# 25EH 4S EFI



## caveman (Jun 13, 2009)

This is a 06 motor and i would like to get a little more speed out of it.It only has about 10 hrs. on it, it is on a 1648 and will do about 23 mph.I was thinking of changing the prop. The boa

t is not here now so i do not know what the pitc is but i do remember it is the low. around 10 would a 13 or 14 be worth the money i would like speed around 30 mph.


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## Quackrstackr (Jun 13, 2009)

It all depends on how many rpm you are currently turning. You need to figure that out before you start jumping up in pitch. 

Your engine is designed to run in a recommended rpm range. Running above or below that at wot is a sure bet for engine problems sooner rather than later.

Every inch of pitch increase is going to knock you down approx. 200 rpm.


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## caveman (Jun 13, 2009)

yes i know this but how do i fig rpms in. right now if i run wide open it over reves


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## Quackrstackr (Jun 13, 2009)

You have to put a tach on it to figure that out.

It is hitting the rev limiter?


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## caveman (Jun 13, 2009)

Dont have,just wanted to know if any one else has this motor and what prop they are runnig,or what is the best way to fig out


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## caveman (Jun 13, 2009)

OK Q You have been very help full in the past please sent me in the right way now


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## Quackrstackr (Jun 14, 2009)

A lot of guys run these on small outboards.

https://www.tinytach.com/tinytach/gasoline.php


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## cathunter21 (Jun 14, 2009)

im not trying to steal your thread :lol: but i have a 07 15 hp mercury and when i there is no differince in 3\4 throttle and full throttle speed wise, and when i do put it on full throttle which i dont it doesnt run smooth it sounds like something is limiting it. i didnt no they had rev limiters on them? i dont no what pitch prop i have but could a higher pitch prop solve this problem?


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## Quackrstackr (Jun 14, 2009)

It is near impossible to diagnose a pitch issue or suggest what you should do without knowing what rpm you are turning at wot and what the recommended range for your engine is.


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## caveman (Jul 16, 2009)

Ok can't find paper work but here is #s on prop. 48 896890a10 8p. I think this is a 8 pitch if i go up in pitch will this increase or decrease RPMS. Right now the motor says max rpm 6000 / over rev. 6300 This motor will over rev when wide open. with this prop.



THANKS caveman/mike


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## caveman (Jul 16, 2009)

ok reread tread and if i understand up in p rpms go down so how much up in p to need to go to get max .performance out of this motor?? :?:


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## bassboy1 (Jul 16, 2009)

If you increase pitch, the RPMs drop. As Quack said, you need a tach to determine what prop you need - period, end of story. Get a tach, get an RPM number and come back. Otherwise, we are purely working off of guesswork, which is never a good idea when it comes to working with precision mechanical devices. We can't help you if you can't give us the RPM you are turning currently.

You aren't by any chance a musician are you? If you have a musical tuner, you can determine RPMs fairly closely, just by determining what note the motor is playing, and whether it is flat or sharp.


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## caveman (Jul 16, 2009)

bassboy1 BOY :lol: :lol: :lol: :lol:


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## caveman (Jul 16, 2009)

I am just looking around here to see if anyone has did this to a motor like this and if so what they did please give good info not smart !#$ INFO...........................................................


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## stinkynathan (Jul 17, 2009)

caveman said:


> I am just looking around here to see if anyone has did this to a motor like this and if so what they did please give good info not smart !#$ INFO...........................................................



Dude....seriously. GET A TACHOMETER! The TinyTach is around $30 and will show up on your doorstep in about four days. I just installed one on my boat after having some timing issues and it has been very helpful. You WILL be glad you installed it. 

No one can really help you other than guessing unless you can tell us what RPMs you're running.


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## Quackrstackr (Jul 17, 2009)

caveman said:


> please give good info not smart !#$ INFO...........................................................



Nobody here doing that. If you won't get a tach, we can't help you with max performance.

If you are currently hitting the rev limiter with an 8, you need at least a 10 to get it off the limiter and (maybe) into the recommended range. You won't ever know how to adjust up or down after you get it off the limiter without a tach.

You can't rely on someone else's prop results unless they have it on the same exact hull with the same exact motor height, etc.


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## TrackerTom (Jul 17, 2009)

If you are really wanting to try to get close without adding a tach, I would try this prop calculator.

https://www.dansdiscountprops.com/BuyNow/propWizard.cfm

I haven't ordered one from them yet, but it does recommend the exact size and pitch that was recommended by my boat manufacturer and came on my boat. Mine performs well, though I still don't know if it is max performance because I haven't added a tach yet either. It does perform well though. The above length will let you put in your exact combo and come pretty close.

Tom


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## Quackrstackr (Jul 17, 2009)

I just ran my boat through that calculator and the majority of the recommendations are way low on the pitch for it. Plus, it is only making suggestions on the Turning Point props that Dan's carries.


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## bassboy1 (Jul 17, 2009)

caveman said:


> I am just looking around here to see if anyone has did this to a motor like this and if so what they did please give good info not smart !#$ INFO...........................................................


I wasn't kidding when I said you could get RPMs based off the musical tuner. All motors make a certain pitch when running at a certain RPM. Each note is a couple hundred RPM away from the previous. Couple that with whether it is playing flat or sharp, and you can get the RPM fairly close - usually within 100 of correct with a tuner.


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## Specknreds (Jul 17, 2009)

Hope you get some useful info out of this.

I have a 25hp 4 stroke Yamaha on a very heavy 1448 modV. I have tried 4 different props. It came with a 10 1/8th x 10 7/8.

10 1/8 x 12 . I jumped to 29 MPH with heavy load and two people. Good hole shot and I mainly use this one.

10 1/8 x 13 With just me in the boat, 30- 32mph. Too slugish too plain with two people. I use this one when I'm solo fishing.

10 1/8 x 11 1/2 Had a 2-3 MPH jump. Brought it back too dealer and exchanged for the 12.

There is no doubt you can not properly prop your boat without a Tach. I will get one, one day. I was lucky and my boat dealer will let you exchange props.


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## caveman (Jul 17, 2009)

OK 
If i get a tach what should i be looking at? I am trying to finish my mod and nothing is working right,and money for tach is not in my budgget right now or is prop. just looking at what i would like to do.
thanks. mike


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## Quackrstackr (Jul 18, 2009)

First thing, if you know that you are hitting the rev limiter... you need to get at least a 10 pitch prop.

It looks like even a 10 was on the low side for Specknreds.

A tach really isn't going to help you much if you are hitting the limiter currently but the Tinytachs are about $30 and can be purchased online. The tach is going to help you fine tune after you get into the proper range... but it takes $ to do that, also. It is hard to find a dealer that will let you swap props until you find the one you like. Specknreds is extremely lucky. My dealer was letting me swap with what he had in stock. I clipped a sandbar that I had no idea was there and scuffed the face on my current prop so that's now what I'm stuck with. At least until I have a few hundred dollars burning a hole in my pocket to start tweaking again.


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## taxidermist (Jul 19, 2009)

cathunter21 said:


> im not trying to steal your thread :lol: but i have a 07 15 hp mercury and when i there is no differince in 3\4 throttle and full throttle speed wise, and when i do put it on full throttle which i dont it doesnt run smooth it sounds like something is limiting it. i didnt no they had rev limiters on them? i dont no what pitch prop i have but could a higher pitch prop solve this problem?




There is either an electronic rev limiter or the valves are floating. I have the same motor and depending on the weight in the boat I hit the same knock. If I have additional weight in the boat I dont hit it.


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## caveman (Jul 19, 2009)

Quackrstackr
Just got back from lake and i am going to get a tack and new prop.... It is a pain to all ways keep looking back at the warning light to see if it is over rev. I just got to find paperwork for this motor to see what props are available 8p was the low end and if i remember correct 14p was high. I just may do like i did as a fo and shoot for the middle and adjust from there.just hate to waste cash. but then a boat is a hole you just keep putting money into.........
Thanks for your help


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## caveman (Jul 25, 2009)

OK i placed my order from tiny tach last night and i hope i will have before next weekend.after i get some #'s i will need help from here.


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## caveman (Aug 1, 2009)

Well it has been a week and i still didn't receive the tach,just waiting is the hard part.I would much rather walk in some place and walk out with what i want.In the mean time i have been looking on line prop selector.And with their recommend a 9.25 diameter pitch 12.5 this is basted on weight.Let me say that i am not going to get this prop. or any other one until after i know my rpms.Just want to know if that prop is in the ball park.
Thanks
mike


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## BassNBob (Aug 1, 2009)

Caveman, if your going to the Dale Hollow get together I will loan you mine to use that weekend.


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## caveman (Aug 1, 2009)

BassNBob said:


> Caveman, if your going to the Dale Hollow get together I will loan you mine to use that weekend.





bassnbob
thanks i would like to go but i need to get my boat finished first.Hope to have tach some time this week am going to call them Monday and see what is up.i may try and go for sat. just not sure. But thank you


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## caveman (Aug 5, 2009)

OK 
I called to day and they said it was being made 2 weeks????? well i will see.


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## caveman (Aug 7, 2009)

STILL NOT HERE.


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## caveman (Aug 12, 2009)

WELL AT LAST it showed up today,it was to late when i got home to play with but after work tomorrow i will look at how it dose with ears and this weekend i hope see on water. :| :|


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## caveman (Aug 13, 2009)

Well today i was able to put tack on my motor and see what rpms i am running with ears/muffs and setting in driveway at idle the tinytack said after 1 min. of running avg. was 440 rpms. is this a point to start at?Is this to low /i will post more info. when i put it on water.Now is when i need input.
THANKS MIKE
PS i have pic's of how it is hooked up and of rpms can post if need be. :?:


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## Zum (Aug 14, 2009)

I didn't look back but I thought this was a prop. thread?
Just knowing what your idle is,is not going to help anyone decide on the proper prop.
Sorry,if this is more then a prop thread.
If it doesn' stall and idles in gear fine,I'd say thats good to go.
People need to know what the rpms are in WOT and don't try that with muffs or even in a barrel.


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## caveman (Aug 14, 2009)

Zum said:


> I didn't look back but I thought this was a prop. thread
> Yes this is about prop but everyone on here said i needed a tack for rpm before i could get the correct prop so i got one.. and i hope that i will get some good in put from the members on here as to what i need to do.After i put it in the water with some good # s.Just wanting some help.
> 
> mike


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## Zum (Aug 14, 2009)

I'm sure you will get some.


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## Quackrstackr (Aug 14, 2009)

440 sounds like you are in the neighborhood at idle.

The problem you are going to have is trying to figure out what pitch to get on the first shot. If you are hitting the limiter, you know right off the bat that you need one at least 2" bigger in pitch. You'll want to try and stay as close to that 6000 number as possible without running over it and you can figure 200 rpm up or down for every inch of pitch up or down... given that you stay with the same model of prop. Increased cup, diameter or adding a blade will cut down your rpms as well.


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