# 25hp Mercury is Sloooow.



## TinCan2 (Jul 11, 2010)

I'm trying to bring a 1989 Merc back to life. I rebuilt the carb and tuned the motor up. Crazymanme2's advise fixed my starter problem (bad solenoid), thank you. Now the problem is no speed. Motor starts fine and runs good, but there is no speed. I know I'm pushing a bigger boat (1648 Seark) but would think I would get a little more speed. On today trip boat would not even plain out. I would estimate speed at around 10 to 15 mph on todays trip. At full throttle it seams there should be more in the tank, doesnt seam or sound like motor is wound up all the way. Is there something I can do?


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## crazymanme2 (Jul 11, 2010)

Need some more info,as where is your tilt pin position,look down the throat of the carb to make sure your getting full throttle,how loaded down is your boat,maybe a pic of the motor on the transom,(side pic)did the motor ever run good? :?:


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## lckstckn2smknbrls (Jul 12, 2010)

Are both cylinders firing?


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## Troutman3000 (Jul 12, 2010)

lckstckn2smknbrls said:


> Are both cylinders firing?



This. It sounds like what mine was doing while running one one cylinder.


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## TinCan2 (Jul 12, 2010)

We will see if this picture attaches. If so it is a copy of my setup. Motor tilt pin was on the third hole from the back. I moved it to the fourth, haven't tried that position yet. Boat weight is 297lbs. I have added gear (batteries, fuel cell, tackle, etc) of an estimated 160lbs plus my weight of 190lbs, so weight it is pushing is an estimated 350lbs. I looked and the paddle in the carb is exactly horizonal at full throttle. I just got the boat (it was given to me) and dont know how it ran before. As you can see it is the long shaft.

I thought about could be firing on one cylinder, will check it this evening. Any pointers on the easiest way to do this?

Feel like I am replacing the motor one part at a time!


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## Troutman3000 (Jul 12, 2010)

TinCan2 said:


> We will see if this picture attaches. If so it is a copy of my setup. Motor tilt pin was on the third hole from the back. I moved it to the fourth, haven't tried that position yet. Boat weight is 297lbs. I have added gear (batteries, fuel cell, tackle, etc) of an estimated 160lbs plus my weight of 190lbs, so weight it is pushing is an estimated 350lbs. I looked and the paddle in the carb is exactly horizonal at full throttle. I just got the boat (it was given to me) and dont know how it ran before. As you can see it is the long shaft.
> 
> I thought about could be firing on one cylinder, will check it this evening. Any pointers on the easiest way to do this?
> 
> Feel like I am replacing the motor one part at a time!




Easy way is to pull the plugs and ground them to the motor, crack the motor and if it sparks then you are good. You can also get a spark plug tester, which is the preferred method.


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## Troutman3000 (Jul 12, 2010)

https://www.tinboats.net/forum/viewtopic.php?f=4&t=14596&p=149862#p149862

Read here, many of the same questions.


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## Troutman3000 (Jul 12, 2010)

Its not your prop is it? Same one that came with the boat right?


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## Quackrstackr (Jul 12, 2010)

TinCan2 said:


> doesnt seam or sound like motor is wound up all the way.



most likely not a prop issue unless it is way overpropped.


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## crazymanme2 (Jul 12, 2010)

Looks like your cavitation plate is well below bottom of your boat.Your boat might be designed for a short shaft, which with the shaft so far in the water would create more drag.
Make sure your motor is firing on both cylinders as mentioned before you mess with the tilt & height of the motor.


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## Deadmeat (Jul 12, 2010)

That was my thinking also after seeing the pic. It looks like a long shaft motor on a short shaft transom.


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## TinCan2 (Jul 12, 2010)

Had a friend look at the timing advance. He got a little umph out of it. He also suggested I raise the jack plate atleast another 3 inches. Will try that and let everyone know how that works. Checked and it is definantly firing on both cylinders.


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## Troutman3000 (Jul 12, 2010)

probably needs to be raised a bit for sure.


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## TinCan2 (Jul 12, 2010)

Ok, got home from work tonight and lifted the jack plate three inches. Put hotter NGK plugs in it and motor seams to run a lot stronger. Will have to throw it in the lake tomorrow to let you know how things worked out.

Attached picture shows the motor after the jack plate was lifted three inches. Does this look like it will be enough? Will have to do some fabrication work to take it any higher.


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## lckstckn2smknbrls (Jul 12, 2010)

I have a 1" thick piece of hardwood on top of my TH Mini Jacker to raise the motor a little more.


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## TinCan2 (Jul 12, 2010)

lckstckn2smknbrls do you think it needs to go higher? I could do the wood think. I'm an accountant for a large metal fabricator/manufacturer. I have the materials and labor available to lift the transit out of AL if needed. I like the durability of AL better; but, I'm sure your suggestion will be fine. Thanks you for the input, I appreciate any ideas.


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## crazymanme2 (Jul 13, 2010)

If you know what the cavitation plate is you want that even or just above the bottom of your boat.


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## lckstckn2smknbrls (Jul 14, 2010)

TinCan2 said:


> lckstckn2smknbrls do you think it needs to go higher? I could do the wood think. I'm an accountant for a large metal fabricator/manufacturer. I have the materials and labor available to lift the transit out of AL if needed. I like the durability of AL better; but, I'm sure your suggestion will be fine. Thanks you for the input, I appreciate any ideas.


Aluminum would be better I had the wood sitting around. My anti-cavitation plate is about 2" above the bottom of my boat. You can raise your motor a 1/4" higher for every 1" you have it set back. The Mini Jacker has a 4" setback.


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## TinCan2 (Jul 14, 2010)

I took the boat to a local lake last night to try the motor with current setup. Results were a lot better. Plained out and ran faster than it has ever. I estimate the top end speed to be in the low 20s mph. I don't have a way to check actual mph. At top end of the throttle the waterline on the motor was at the bottom of the (I guess cavitation plates) two rings/plates just above the foot (see photo above). I know this is a lot of boat for a 25hp. Do you think it could do better on speed or am I at the max? Good news is I can live with its current output. More speed is always better if you can get it!

I attached photos of the "trail" the boat was cutting and a picture of boat for size reference. Does the "trail" look about right?

Everyone please excuse me, I'm new at rigging tin boats. In the learning curve. I appreciate everyones help.


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## Troutman3000 (Jul 14, 2010)

That motor is plenty for that boat, but without having a mph reading its hard to tell if your getting everything out of it. The motor setup looks like the cavitron plate is still a little low according to Lock and Stocks....


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## Zum (Jul 14, 2010)

I agree with the above post.
If it's in the budget maybe some type of tach could be installed.(tiny tachs are pretty cheap)
You may not have the right one(prop),which not only makes the boat slower but it's hard on your outboard.


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## lckstckn2smknbrls (Jul 14, 2010)

Raise the motor more just watch the the motor is peeing.


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## TinCan2 (Jul 18, 2010)

I raised the motor so the cav plate is level with the bottom of the boat. Took it to the lake for a trial run with my iPhone speedo app. Messed with the tilt pin to get it to the point where it ran the best. After all that the iPhone read 21mph. Does this sound about right for my boat and motor? Would think it could do a little more. I was expecting mid 20's. I can live with it the way it is now, just wanting to know if I could get more out of it.


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## TinCan2 (Jul 18, 2010)

A little more information, I looked at the prop, it is a "Power Prop" 13 pitch.


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