want more top end

[aintmisbehavin]

Re: want more top end

If your motor is only turning 5050 @ WOT, you can expect significantly reduced life. I would try raising the motor first based on your other thread before buying another prop.

why would this reduce life? does everyone run their boats at WOT at all times. Its a 76 johnson 115. Not sure how much life it actually has left anyway.

Compression is 120 +/- 5 on all cyl
Ignition, plugs, battery and everything is good
Fuel pressure is good.

Boat is running great, just want to do a little tuning. Had no idea how to set a outboard up.

 

[coolguy147]

Re: want more top end

its something called lugging. when you lug the motor bad things happen. excessive carbon build up. possible overheat. streess on thing where stress doesnt need to be.

 

[R.Johnson]

Re: want more top end

It's a gasoline burning engine, such as the family car. Think of locking the family car in high gear. Add a hill, and see how it respond's.

 

[aintmisbehavin]

Re: want more top end

Cupped prop, I have no idea

here's the one i bought

http://boatpropellers.iboats.com/Jo...10025/?**********=738861582&*******=294051844

 

[aintmisbehavin]

Re: want more top end

Seems like a set up issue. Photo of the stern with the cav plate would be a big help. May need to raise the motor up some.
I will ask again.....cupped prop ????

Here is a pic attached to another thread
http://forums.iboats.com/showthread.php?t=361649

 

[Fisherball]

Re: want more top end

The prop got rid of my low end vibration.

Shortly after I replaced a dinged, damaged prop my prop shaft seal started leaking. That low end vibration caused the seal to fail. Not hard to replace, you need a manual to tell you what to do.

 

[kenmyfam]

Re: want more top end

Cupped prop, I have no idea

here's the one i bought

http://boatpropellers.iboats.com/Jo...10025/?**********=738861582&*******=294051844

Well it says representative photo only so your guess is as good as mine.
How about a photo of the one you got ???

 

[kenmyfam]

Re: want more top end

Motor looks low. raise it a hole at a time and see what happens. Make sure you are still cooling each time though.

 

[Fisherball]

Re: want more top end

Click the product info tab on the ad in link, it lists:

Fine tuned cupping - grips the water tight and greatly reduces ventilation

You have a cupped prop.

 

[aintmisbehavin]

Re: want more top end

So whats a cupped prop going to do?

 

[reeldutch]

Re: want more top end

were did it say it is a cupped prop.

if your 17 pitch prop turned more rpm than the 15
you have a problem.
are you sure about the rpm readings?
i didnt think your engine is set to low i believe if you fully trim it in as you should the cavitation plate wil be above the keel.
but i cant realy tell.

but everybody here is telling you thigns to do,
Rememder to stick with one thing at te time or you will not know what to do next.
go with th easyest for you and tell us your findings.

everybody here will agree that the same type of prop with a lower pitch should turn more RPMs assuming your engine is in great shape.

start from there. i would take your old prop and your new prop to a prop shop and tell them your story
they might see a problem with the old prop.
bud if thats the case im woried about the rpms the 17 pitch let the motor spin when the prop was brand new.

 

[Fisherball]

Re: want more top end

Check your lower unit oil every time you get off water. Pull bottom screw & be sure what flows out (won't be much) is oil not that peanut buttery, milky looking stuff that is water & oil mixed. A dinged or out of balance prop causes that vibration that wears out seals.

 

[aintmisbehavin]

Re: want more top end

I raised my engine up 2 holes and still have one to go. I was able to get 1 mph from it, so it topped out at 35 @ 5100 rpm's. I can get it up 1 more hole and that shouldn't hurt anything, may even pick up a another mph and some a little more rpm. Still may order a 13 prop and see what that does along with the trim tabs everyone is going to.