# Having problems with motor



## txneal (May 13, 2010)

I just spent two days on the lake and experienced some trouble with my motor, so I'm hoping that some of you guys might be able to help me figure out what I need to look for. The motor is a 1973 Evinrude 25hp with tiller. It runs really great most of the time, but every so often it just seems to suddenly rev up the rpm real high and the prop quits turning. Over a period of two days on the lake, it happened to me about 5 times. It only seems to happen when I am cruising at wot. I'll just be going along just fine and then it will suddenly happen. I can let off the throttle and then it will catch and start turning again. It will run perfectly for a while and then it will happen again! Its as if it just momentarily jumps out of gear and then when I let off the throttle, it goes back into gear. It only happened about 5 times over a period of two full days on the lake, but I'm pretty concerned about what it is and want to find the cause and fix it before I take the boat out again.

If any of you guys have some suggestions for something that might be causing this or anything that I might try to correct it, I would really appreciate the assistance. This has never happened to me with this motor in the past, but I was carrying more weight this time than what I have ever carried before. It is a 14 foot semi-v starcraft and I had a guy up front and then about 20 gallons of water in a bait tank toward the rear/center of the boat, and also a bunch of fishing gear.. I thought that maybe the extra weight might have something to do with it, but I have no idea what it is.


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## Westtnman (May 13, 2010)

Sounds like it may have spun the rubber hub in the prop. Relatively cheap fix at the prop shop. Also, if you have had the prop off for any reason might check to see that the prop nut is torqued down properly.


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## crazymanme2 (May 13, 2010)

I believe that motor has a shear pin because I have a 1976 25hp & it does.Pull your prop & check the pin.


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## Rat (May 13, 2010)

Definitely check the shear pin, I'll bet it is sheared. Also, you may be ventilating, but this is less likely. If it hasn't happened before, and you have made no changes, then it shouldn't be ventilating; more weight would not make it ventilate. However, if you have moved to motor up on the transom or you are in a higher trim/tilt hole it could.


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## russ010 (May 13, 2010)

exact same problem I had with my 20hp johnson...

Changed the prop and it solved everything.. the rubber hub in the prop is shot


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## txneal (May 13, 2010)

Thanks for all of the replies so far. I'm glad to hear that it may just be in need of prop attention because I was getting worried that there might be something more serious going on in the lower end. I'm at work right now, so I can't look at it until I get home this afternoon, but I'll definitely pull the prop and check it out. That is the only prop I have and it is ancient and a little dinged up, so I've been planning to purchase a new prop anyway. This could certainly be the motivation I need to get it ordered. So If the pin was sheared or the rubber hub is spun, it could still turn most of the time and just slip occasionally? Yesterday morning, I ran it for about half an hour and it slipped twice during that time. Then, I went a few of miles up the Colorado River and was facing a strong headwind and some significant waves and it just pushed along with no trouble at all.


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## perchin (May 13, 2010)

Sorry to be the one who does not beleive this is your prop hub but I don't. I've spun many props and have never had one that works most of the time under a load and only free spins once in a great while. Mine all worked at only idle speeds and free spun under any load when it was the prop. I went through 6 props on my last boat due to the harsh lake we love so much... :twisted: Any ways I really hope you prove me wrong on this one. Now as for the shear pin, I have never had that problem, so maybe its that. Best of luck man.


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## txneal (May 13, 2010)

Well, perchin, I was wondering how it could be working most of the time and just slipping occasionally if it is a spun hub or sheared pin. My thinking was that if it was a pin, it would just spin free all the time and not be working at all. Then again, I haven't ever experienced this before, so I don't know what to think about it. If it turns out that it isn't a problem with the propeller, then where should I focus my attention next?


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## perchin (May 13, 2010)

For now let's just [-o< that it is indeed the hub, or shear pin. I don't know much more about the inside workings of an lower end on an outboard. I'm sure someone who does though will be able to help if need be.


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## russ010 (May 13, 2010)

When you are getting up to WOT, you get going then all of a sudden the motor just revs up, you slow down, let off the throttle and it starts back up again - and then it will do it again about 5-10 seconds later... usually only happens when you are wide open, or when you are on your way to full throttle. Happened to me nearly every time I was out. Some days it wouldn't do it at all, sometimes only once.

It's funny man, but I know exactly what you are dealing with. I had an OLD prop on mine too.. when I took it to my repair guy he told me he thought it was the hub, but wouldn't know until he got into it. When I got there, he had the new prop on and said the hub was jacked up and would catch and wedge itself, that's why it would run sometimes and not others. 

Props are about $100 and comes with the hub... go ahead and spend the dough - and wait til you see how much better your engine runs after that. I couldn't believe the difference


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## txneal (May 13, 2010)

Russ: from what you describe, you were experiencing exactly what is happening with mine. Since I planned to get a new prop anyway, I'm going to give that a try. If I take the prop off and look at the hub, should I be able to tell that there is something wrong with it?


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## russ010 (May 13, 2010)

I have no idea man... I had the repair guy fix mine so I have no idea what it looks like in there. 

I can work on car engines, but you couldn't pay me to touch a marine motor - that's why I let him fix it while he was tuning it up. Since it's a rubber hub, I would think you would be able to see if it's torn or something like that


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## perchin (May 13, 2010)

You should be able to see if the rubber hub has become seperated from the prop with a spun prop, although the last one I spun was only 2 weeks old and I couldn't see any damage to the rubber, but it was indeed spun.


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## Quackrstackr (May 13, 2010)

You won't be able to tell just by looking at it.

You can even drive the hub out of the prop and still not be able to tell unless it has galled the rubber.


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## perchin (May 13, 2010)

Quackrstackr said:


> You won't be able to tell just by looking at it.
> 
> You can even drive the hub out of the prop and still not be able to tell unless it has galled the rubber.



huh???? 5 out of 6 I could visibly tell without question that they were spun. As in black streaks on the inside edge of the aluminum from the hub spinning in the prop. Also from the little erasor like shavings it seemed to of caused, not to mention the rubber being a lil messed up around the edges.

you should also Remove the propeller from the propeller shaft. Inspect the rear bearing surface of the propeller for circumferential scratches indicating the propeller has been turning at a different speed than the propeller shaft/thrust bearing.


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## Quackrstackr (May 13, 2010)

I guess it depends on the prop design.

I've got 2 of them at the house right now (Evinrude) that are spun that you wouldn't know unless I told you. You can't even see the rubber in them, much less black streaks.


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## txneal (May 13, 2010)

well, I just got home and pulled the prop and I can't see any damage at all. It sure couldn't hurt anything to have a new prop, so I'm going to order one and hope that it will fix the problem. I appreciate the help you guys have given me. At least I now have hope that a new prop will fix it and that maybe there's nothing wrong in the lower unit. It might be a while before I know for sure because I'm getting ready to leave for Germany and won't be back for a month. I guess I'll have a new prop to go test out when I get back!


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## bassboy1 (May 13, 2010)

txneal said:


> well, I just got home and pulled the prop and I can't see any damage at all. It sure couldn't hurt anything to have a new prop, so I'm going to order one and hope that it will fix the problem. I appreciate the help you guys have given me. At least I now have hope that a new prop will fix it and that maybe there's nothing wrong in the lower unit. It might be a while before I know for sure because I'm getting ready to leave for Germany and won't be back for a month. I guess I'll have a new prop to go test out when I get back!



A new prop is never a bad idea. Keep the old one in the boat. One day, when you find the shallowest rock in the lake at WOT, you'll be glad you have the spare. You can idle back to the dock with a spun prop a lot better than you can make it back with a prop lacking all 3 blades.


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## flintcreek (May 13, 2010)

Keep us posted and let us know what happens when you put on a new prop. I have a 35 hp Johnson doing the same thing, I have just acquired a extra prop and will give it a try in the next few days. Somewhere on this forum I have read about a motor doing the same thing and it being a worn clutch dog, which engages the gears and then pops out at WOT causing the same symptoms.
I have spun a hub before on another motor and after it was spun, it always spun on me at WOT. If the prop does not fix both our motors we may have to search out more info on the clutch dog. Keeping my fingers crossed.

Flintcreek


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## txneal (May 13, 2010)

flintcreek: I'm just finishing up a job and will be too busy to get to the water before I leave for Germany, so it will be about 6 weeks before I can go test out a new prop. There is the slightest possibilty that I might be able to get a prop and run up to the lake before I leave, but it is unlikely. In the meantime, I'll be very interested in knowing if the new prop has corrected your problem, so please post back here as soon as you have given it a try. A worn clutch dog sounds like way more work than replacing a propeller , so I've got my fingers crossed on this one.


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## cajuncook1 (May 14, 2010)

You can check by putting a mark with a water proof marker pen across the prop and the end of the shaft. If the mark on the shaft does not line up with the mark on the prop after a run it's spun. Look at the two white lines in the picture.








You can take it to prop shop or dealer and get it priced to replace the hub, if that is the problem. Rehubbing might be cheaper.

Good luck my friend,

cajuncook1


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## txneal (May 14, 2010)

Thanks for that great idea cajuncook. I'm actually pretty sure now that it is a clutch dog. What I failed to mention in my previous description of the problem is that there is also a loud "clunk" sound associated with when this happens. In fact, the fist time it happened, I thought I had hit a submerged tree and sheared the pin. 

I just got off the phone with the nearest boat repair guy...about 150 miles from me...and I described the problem to him. He says it is almost certainly the clutch dog and that I'm probably looking at up to $600. for the repair bill with parts and labor. Not very good news since I might be able to find another used motor for not much more than that. He says he hasn't looked up the price, but wouldn't be surprised if the clutch dog/forward gear assembly will be about $400, just for parts.

According to this guy, if it were a spun hub, I wouldn't be getting the "clunk" sound everytime it happens, so I'm pretty sure now that I'm dealing with a clutch dog issue.

Another idea would be to purchase a remanufactured lower unit. I've seen some available for about $400 or maybe I could stumble across an even better deal somewhere. The mechanic I talked to said that installing a remanufactured unit would be something I could easily do myself without having to bring it in to him. Is this something that simply bolts on and is good to go? No special knowledge or tools required?

I guess I'll need to do a little research and see what I can find. I still intend to get a new prop regardless of what I do about the clutch dog.


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## russ010 (May 14, 2010)

are you going to try replacing the prop and all still? I had the clunk happening too - it started doing that crap to me while I was out on the water at night, and I thought I had hit a log or something

but it may very well be the clutch dog - but I have no idea... sucks that your nearest mechanic is 150 miles away


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## cajuncook1 (May 14, 2010)

txneal said:


> Thanks for that great idea cajuncook. I'm actually pretty sure now that it is a clutch dog. What I failed to mention in my previous description of the problem is that there is also a loud "clunk" sound associated with when this happens. In fact, the fist time it happened, I thought I had hit a submerged tree and sheared the pin.
> 
> I just got off the phone with the nearest boat repair guy...about 150 miles from me...and I described the problem to him. He says it is almost certainly the clutch dog and that I'm probably looking at up to $600. for the repair bill with parts and labor. Not very good news since I might be able to find another used motor for not much more than that. He says he hasn't looked up the price, but wouldn't be surprised if the clutch dog/forward gear assembly will be about $400, just for parts.
> 
> ...




txneal,

I would definitely try the spun hub assessment(cheaper route) and if it truly your clutch dog, then I have supplied a couple of links that my get your attention, especially the price of a new clutch dog. I think the mechanic was feeding a big profit in his pocket pitch.

This is a break down of your gear case. Look at item number #31.

https://www.boats.net/parts/search/BRP/EVINRUDE/1973/25302A%201973/GEARCASE/parts.html

*You can order service manual and do it your self.* 8) 

https://cgi.ebay.com/ebaymotors/1973-Evinrude-25-hp-sportster-service-repair-manual-omc-_W0QQcmdZViewItemQQhashZitem3ca98c48fbQQitemZ260542580987QQptZMotorsQ5fManualsQ5fLiterature

https://cgi.ebay.com/ebaymotors/1973-Evinrude-sportster-service-manual-repair-25-hp-_W0QQcmdZViewItemQQhashZitem3cac8db7c0QQitemZ260593006528QQptZMotorsQ5fManualsQ5fLiterature

If you get the service manual and decide to replace the clutch dog yourself don't forget to get a gear case seals kit. Call the Boats.net number and they can assist you with purchasing one. Probably about $30 or less. Don't forget to drain the gear oil first :lol: or it will be a big mess. Refill the case after you done.

Hear is a link on how it is done (draining the gear case and refilling by the Marine Doctor)

https://www.youtube.com/watch?v=Wj0la6c5FDg

You will really like this video!!

https://www.youtube.com/watch?v=vuAcrDFvApA&NR=1

Good luck my friend!

cajuncook1


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## txneal (May 14, 2010)

Thanks for all the links. I quickly checked a couple of them, but will spend more time on it after work today. The mechanic I talked to did say that he thought the clutch dog AND forward gear would probably need to be replaced. I'm wondering how difficult it would be for me to open it up and just inspect it myself to see what needs replacing? Is there a way to get to it in order to view it without having to completely disassemble everything?

I really love this motor as it seems a perfect match for my boat, so I sure would like to have it in top condition. I realize that I may have to invest some more money into it to achieve that, but it'll be worth it to have a dependable motor. At the same time, I'd like to keep the cost down as much as possible. Thanks again for all the help and I will definitely be checking out those videos and other links this evening.

...and, yes, I still intend to try a new prop


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## blimp (May 14, 2010)

it isn't hard to get into that year's lower unit to inspect all you need to do is drain the lower unit oil and remove the screws that hold the bottom plate in place. Draining the oil will likely tell you if you need any parts as it will have metal shavings in there if there is a lot of wear and tear. 

But before you go into that, i would wait and see if it is your prop, easy, cheap fix. Changing your lower unit oil to inspect for metal is an easy thing too that should be done 1-2x season anyway...

good luck, hope its only the prop.


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## txneal (May 14, 2010)

I would like to think that it is only the prop, but I'm planning for the clutch dog anyway. Maybe I'm a pessimist, but I want to be prepared for whatever it is. The main difficulty I'm having right now is the fact that I'll be leaving for Germany soon and will be gone for an entire month. I was hoping to get right back to fishing as soon as I return, so it'll suck to be coming back to a motor that needs work. Therefore, I'd like to be able to inspect the clutch dog and forward gear so that I can get parts ordered if I need them. I suppose the smart thing to do would be to open it up and see if I can see a damaged clutch dog/forward gear and, if so, get parts ordered asap. If they don't appear damaged, then I guess I'll expect the prop to fix the problem. Either way, I'm getting a new prop....that was already in my plans before any of this happened. I'm assuming that if the clutch dog and/or forward gear is damaged, I should be able to tell by simply inspecting them?


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## cajuncook1 (May 14, 2010)

check the ebay links with the service manual listed.....its worth its weight in gold. It has step by step pictures and tutorials that will be a tremendous help!!!!!!! Less than $25 and will help you maintain and service your motor for years to come.

cajuncook1


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## txneal (May 14, 2010)

I actually already have a copy of that service manual that I bought from eBay about a year ago, so I'm good to go there. I was just searching craigslist and found a motor for sale that is identical to mine. The guy says it was running fine until he started having trouble with it only reaching half speed....says he thinks it needs coil He's asking $250 for the motor as is. I'm wondering if it might not be a good idea to just buy that and hope the lower unit and prop are in good condition? It would also give me an extra of everything in case I should need other parts in the future. Still weighing my options, but a parts motor sounds pretty enticing right now.


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## flintcreek (May 15, 2010)

txneal, I have read some where on the net about someone that had the clutch dog ears welded up and then machined down, and sometimes if it has just started jumping in and out of gear you do not have to replace the forward gear. It might be worth trying to find out more info, before you order parts.

Flintcreek


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## crazymanme2 (May 15, 2010)

I've welded gears on that exact same motor.No big deal other than taking apart.I tig welded the worn part than filed it down.


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## txneal (May 16, 2010)

I think I've finally come to a decision on this. I found a guy who is selling a 1971 model of my motor. Although his is 2 years older than mine, most parts are identical and the lower units are the same. He says the lower unit on his is good and it's a complete motor, so it may come in handy for all sorts of spare parts in the future. Another plus with this deal, I think, is that it comes with a prop that recently had the hub rebuilt, so I should be able to take care of the prop question as well as the clutch dog at the same time. He's asking $250. for the motor, so I think that it should be a good deal if I can just switch out the lower units and props and be back on the water. Additionally, he says the motor runs, but has some issues, so I'm thinking that it may even be possible to eventually end up with a working spare motor. I'm thinking that regardless of any other considerations, if his lower unit and prop will fix my problem, then I've gotten off pretty easily and inexpensively on this deal.

My main concern is that I'm not wasting a bunch of time fooling around with this motor when I get back from Germany because I'll be ready to do some fishing asap. As I understand it, switching out lower units is a pretty simple job that could be done quickly. If I can just get my boat into the water, then I could take my time with messing with the other lower unit and perhaps even look into the idea of tig welding and grinding that clutch dog.


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## txneal (May 17, 2010)

Since I intend to just switch out the lower unit with another one, I'm wondering what all is involved in doing that. I have a copy of the service manual, but it's always good to hear from people who have done it before. I know that I'll need to drain the oil before removing it and then be prepared to refill with fresh oil after the new one is installed and I'm assuming there will be a gasket required where the lower unit bolts to the exhaust housing. What else do I need to be aware of? Are there other seals that need to be replaced? I supposed the shift linkage has to be disconnected and reconnected to the new one as well. And then does the shaft simply slide up into place through the exhaust housing or is there more work involved in getting it back into place? I've never done it before, so any advice from those with experience would be great!


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## perchin (May 17, 2010)

txneal said:


> Since I intend to just switch out the lower unit with another one, I'm wondering what all is involved in doing that. I have a copy of the service manual, but it's always good to hear from people who have done it before. I know that I'll need to drain the oil before removing it and then be prepared to refill with fresh oil after the new one is installed and I'm assuming there will be a gasket required where the lower unit bolts to the exhaust housing. What else do I need to be aware of? Are there other seals that need to be replaced? I supposed the shift linkage has to be disconnected and reconnected to the new one as well. And then does the shaft simply slide up into place through the exhaust housing or is there more work involved in getting it back into place? I've never done it before, so any advice from those with experience would be great!



I really think I would just throw on the prop from the other motor first. If the problem is still there then I would try and jump into the lower end. just my .02


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## txneal (May 17, 2010)

I probably will just try the prop first, but I want to make sure I have everything available that I will need to make the switch in case I need to. I'm leaving for Germany in exactly two weeks and won't return until July 2nd. If it turns out that I need to switch lower units, I want to have all the gaskets/seals, oil, and instructions ready to go so that I'm not missing much fishing time. If I get that stuff ordered and have it on hand, I'll be ready to make the switch on short notice if I find that I need to. I'm hoping to hear that switching out the lower unit will be a job that can be completed in an hour or so.....??? I talked to a boat motor mechanic on the phone and he told me that if I wanted to just switch out lower units, it was a job that could easily be done at home and wouldn't require bringing it into the shop. I hope that means it is simple and quick!


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## flintcreek (May 17, 2010)

I do agree first try the prop and hope it works, if not then first off drain the oil out of the lower unit you plan to use, check it for metal and if everything looks good then all I would do is drop the lower unit and make sure both lower units have the same shafts and shift linkage, if so put in the new water pump impeller and put it back together. Doing 2 at one time it will probably take a couple of hours. But for the money I would buy the extra motor anyway....Flintcreek


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## duke us (Jan 11, 2011)

I had the same issue. My Mercury motor would be fine at idle and low speed, but when I would have it at WOT, the prop seemed not to catch. The motor would rev up and I would be going the same low speed as before. :? I called a local dealer and he claimed it was a spun hub. I took off my propeller and this is what I saw.






I ordered a new propeller and hopefully that should do the trick!


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## richg99 (Jan 11, 2011)

Remember that you can have that prop hub replaced. Assuming the new prop does the trick for you..I'd then have the hub on the old one replaced. That way, you will have a very low cost spare on hand at all times. 

The last hub I had replaced was about $35.00 ... five or more years ago. We actually had to try three or four different prop hubs to get one to fit properly on the splines. After the second one wouldn't go on easily, I just brought the motor into the shop and we put them on the motor spline first...and when we finally found one that fit properly..he re-hubbed the prop with that one. Strange, but true. 

regards, Rich


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## Howard (Mar 27, 2011)

> had the same issue. My Mercury motor would be fine at idle and low speed, but when I would have it at WOT, the prop seemed not to catch. The motor would rev up and I would be going the same low speed as before. I called a local dealer and he claimed it was a spun hub. I took off my propeller and this is what I saw.




This is what mine did today. It looks ok (HUB), not like yours and I am going to replace the prop. The prop is worn and it goes on a 15 HP. Hope it fixes my problem ...


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