Performance or Prop

[keys disease]

Today got to run boat at WOT, no wife or kids. Only got 40 mph at 4500 rpms. Engine runs great at idle or WOT. Boat is a Key West 186 Sportsman (19 ft cc) with a 2004 Yamaha 150 2 stroke. Prop is a stainless factory prop with a marking of 5070 19. Any help would be loved.............

 

[99yam40]

Re: Performance or Prop

Is 4500 your WOT?

Have you checked out this site to see what props and performance they got?

http://www.yamaha-motor.com/outboard/products/perfbull.aspx

 

[robert graham]

Re: Performance or Prop

Your prop/boat/trim setup should give a wide open throttle in the 4500 to 5500 RPM range. Did you adjust your trim when you were running wide open? If not, then try trimming it up next time for a few more MPH and a few more RPM's. If trimming it up doesn't give you that then you may need a different prop to allow for more RPM's. Good Luck!

 

[rodbolt]

Re: Performance or Prop

that motor needs to be capeable of turning 5300 to 5500 RPM with its NORMAL load.
if not engine longivity may be impaired.
did it ever turn up? has the tach been verified accurate? a quick run up with test wheel YB1626 and the engine should be able to turn it 4600 to 4800 RPM.
if the engine is making correct power chase prop issues, if it cannot you have to fix the engine issue first.

 

[keys disease]

Re: Performance or Prop

I was running WOT. I checked that the carbs were all wide open. I checked the post you recommended 99 yam and they ran a 17 pitch prop. Im thinking a aluminum 17 and I should gain 500 to 600 rpms. Also I trimed engine till it sounded like it was ventiling then trimed it down to acheive the 4500 rpms. Once I get all my info together ( total weight, dead rise, gear ratio etc) Ill post on the prop forum.

 

[robert graham]

Re: Performance or Prop

If your set-up, trim, tach and motor are all as they should be, and I would expect they are, then you're probably going to need a different prop, keep your present prop for a spare. Maybe the previous owner was doing special with the boat that could require a prop like what you've got? Maybe it's never been right. You're really going to like it when you can run your boat/motor in the 5500RPM range. I had a 115 Yamaha on a 16' Checkmate that would cruise all day at 5800RPM, maybe not the best for the motor but it never seemed to hurt it. Good Luck!

 

[rodbolt]

Re: Performance or Prop

if RPM is all you want its cheaper to remove the prop and toss it in the creek.
if actual performance is what your after the ONLY way to do it is either a dyno run OR the use of the yamaha test wheel.
this will put a known load on the engine and you measure the max RPM against a known load.
if it can pull the known load to the correct RPM, chase prop and hull issues.
if it cannot pull a known load to the proper RPM chase engine issues.

 

[robert graham]

Re: Performance or Prop

Is your boat new from a dealer or pre-owned by somebody maybe screwing around with the set-up or prop. If it's new, take it back to the dealer and tell him it's not reaching specified RPM's...

 

[keys disease]

Re: Performance or Prop

Preowned by a bone head.

 

[robert graham]

Re: Performance or Prop

He may have replaced/changed the prop for some reason. If you can return to the "original prop specified" for that motor it'll probably put you right near where you want to be, speed and RPM wise. Do you have your owners book/manual or a boat dealer around who could aim you in the direction of the right prop. Good Luck and let us know what you find!