replacement prop question

[xltier]

Is there a way to find out what prop I should have on my boat.The one on there has no size markings anywhere.It doesn't seem to perform as well as I would expect. Ihave throttle left to go after I am peaked out mph. Its 1995 AQUASPORT 225 EXPLORER WITH A 250 YAMAHA.

 

[jimmbo]

What RPMs are you maxing out at? What is your engines recommended WOT RPM range? I find it hard to believe that you are still have unused Throttle when you reach peak rpm, unless you are under propped and your engine has a Rev Limiter(I have never had one with).

The prop has to have the info on it somewhere.

 

[xltier]

it is maxing out at 58-5900 rpm. i am told that it has a rev limiter. it is a 2003 ox66 250 hp.i know the info should be on it but it isn't.it is off the motor ,on my bench and 3 of us have gone all over it.

 

[jimmbo]

Do you know the the WOT rpm range?

 

[xltier]

6100 I have been told.not positive. but my point is that I am reaching that rpm at 3/4 throttle. anymore throttle movement just makes more sound from the motor but nothing changes.rpm or speed.hole shot is good and up on plane is quick but if I pull back to bring the motor down a little it falls right off plane. constantly playing with the throttle to maintain plane without being wide open.the boat originally came new with a 200hp.when I got it, it has a 250hp.thought maybe the 200hp prop might have got used,that's y I want to measure it.if there is a way to.

 

[jimmbo]

Engines have a Recommended WOT RPM range. examples; 4500 - 5500, 4800 - 5300, 5000 - 6000. At 6100 you are probably over revving, but by how much? You haven't provided the WOT range speced by Yamaha. You also haven't provided any info as to what prop you are currently using. The info is on the prop, you just haven't located it.

"boat originally came new with a 200hp.when I got it, it has a 250hp.thought maybe the 200hp prop might have got used"

The two engines probably utilize the same prop(s). Depending what the gear ratios are on engines, they may or may not use the same pitch on a given hull load, or they may require different pitches.

"hole shot is good and up on plane is quick but if I pull back to bring the motor down a little it falls right off plane."

You are falling off plane with the engine at 5500 rpm? Something here is not adding up.

 

[xltier]

we have polished this prop all over. it is NOT on there.I am a 20 year mercruiser mechanic with a full time repair shop. I just don't know outboards. I will never have another one. also I did not say it fell off at 5500.

 

[Sea Rider]

If prop numbers are unavailable on body or blade, take it to a prop shop and have it measured to know the exact diam and pitch, prop seems is way under propped. Will need to go to a higher pitch prop for wot rpm to decrease. How much more pitch, who knows..

Happy Boating

 

[xltier]

that's what I was thinking. and y I wondered if there was a way to check pitch at home. I just got a call, a guy has a 13 3/4 x19 stainless for me to try.mine is 14x??. also the steel one is cupped and mine isn't. thanks

 

[Sea Rider]

that's what I was thinking. and y I wondered if there was a way to check pitch at home. I just got a call, a guy has a 13 3/4 x19 stainless for me to try.mine is 14x??. also the steel one is cupped and mine isn't. thanks

Will need prop tools to check correct current pitch, available at prop shops. Try the new prop and report max wot rpm achieved as loaded to go from there...

Happy Boating

 

[xltier]

10-4