OMC 2.5L 120HP

[my jenny]

Hi, I was wondering what size prop we should have on; 16'8" Play Time open bow, OMC 2.5L 120HP. New to the pitch/size.

 

[Sea Rider]

Assume you have a current prop with that engine ? If so, need to go for a wot spin you alone on flat calm no wind water cond and check max wot achieved on that run to see if inside min-max rpm range stated for that engine.

Happy Boating

 

[Scott Danforth]

17 pitch or 15 pitch would be my first guess. 19 pitch may work, but you may have a sluggish holeshot

 

[steelespike]

Your present prop size should be near the base of the blades or under the prop nut.

 

[my jenny]

This is the outboard

 

[my jenny]

We are trying to find the problem: WOT only 2000rpm with load,

 

[Scott Danforth]

Check the stickies at the top of the forums for suggestions of low WOT

 

[Sea Rider]

Does the engine revs even throughout the whole throttle range ?
How many people were on board when tested while achieving so low rpm ?
Does tach reads accurate ?
Is prop in good healthy cond, probably you are experiencing nasty hub issues or you have a spun hub already ?
If 2000 wot revs are real, you?re extremely lugging the engine which is no bueno...

Happy Boating

 

[steelespike]

Have you looked under the prop nut for prop size?What is the gps speed at 2000. Probably not on plane.
Have you done a cylinder drop to see if all are firing?

 

[my jenny]

I never thought to use my gps to see how fast we were "NOT" going! LOL....I will do next time. Only my husband and I onboard. The prop we have on there now is 13x19B. Yes the tach seems accurate.

 

[my jenny]

yes we have done a cylinder test and all are firing, we also changed the carb

 

[Sea Rider]

If all of the above is OK seems a prop hub failure....Can you borrow another prop to test ?

Happy Boating

 

[steelespike]

Is this called a Sea Drive or a 400
Is it a V4 2 stroke? Depending on the model there may be only one prop higher so I'm thinking a 17 may get it done though still sluggish.
Gear ratio is 1.86 Everything sound and tuned I think a 19 might work but I think there is a problem.Perhaps the foam has absorbed water over the years.
Is the timing set right and advancing as it should? Throttle opening all the away?