25EH 4S EFI

[caveman]

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.

 

[Quackrstackr]

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.

 

[caveman]

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

 

[Quackrstackr]

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

It is hitting the rev limiter?

 

[caveman]

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

 

[caveman]

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

 

[Quackrstackr]

A lot of guys run these on small outboards.

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

 

[cathunter21]

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?

 

[Quackrstackr]

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.

 

[caveman]

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

 

[caveman]

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?? :?:

 

[bassboy1]

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.

 

[caveman]

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

 

[caveman]

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...........................................................

 

[stinkynathan]

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.

 

[Quackrstackr]

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.

 

[TrackerTom]

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

 

[Quackrstackr]

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.

 

[bassboy1]

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.

 

[Specknreds]

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.