prop question

[Brian_Brunner]

Hey guys, I have a prop question, I have a 89 winner with a 3.0 merc and a alpha one drive and I top out at 30mph @ 3400rpm here in colorado, i bought it in florida and it ran 35mph @ 4000rpm, my question was what prop should i be running here in colorado for max mph and rpm? i have a 14 3/4 19 pitch on it now, Basically WHAT should i be running on it?
Thanks Brian

 

[Bondo]

Re: prop question

Ayuh,... I'd think a 15" might get it up to the required 4200/ 4600 rpms...

 

[steelespike]

Re: prop question

I think you have more than an elevation problem.If the Winner is 17 to 19 feet you should be running close to 40 or more at sea level and about 4600 rpm. Be sure the motor is in excellent tune and the throttle opens all the way.Bottom clean and smooth.Check the compression.
You can figure about 3% power loss for each 1,000 feet, thats with ideal tuning for that elevation.If you will be running routinely at that elevation you should rejet the carb.Not sure but its possible timing may be an issue at extreme elevation.If your sure motor is sound and your specs remain the same Bond-o s suggested prop should work.Otherwise get us the new specs
so we can suggest a change.

 

[Brian_Brunner]

Re: prop question

Ok I will check timing, but will the pitch of the prop affect it that much?

I think you have more than an elevation problem.If the Winner is 17 to 19 feet you should be running close to 40 or more at sea level and about 4600 rpm. Be sure the motor is in excellent tune and the throttle opens all the way.Bottom clean and smooth.Check the compression.
You can figure about 3% power loss for each 1,000 feet, thats with ideal tuning for that elevation.If you will be running routinely at that elevation you should rejet the carb.Not sure but its possible timing may be an issue at extreme elevation.If your sure motor is sound and your specs remain the same Bond-o s suggested prop should work.Otherwise get us the new specs
so we can suggest a change.

 

[1980Coronado]

Re: prop question

Ok I will check timing, but will the pitch of the prop affect it that much?

Yes...rule of thumb is 150-200 rpm for every inch in pitch and cupping will reduce rpm by 200 rpm......you have altitude reducing your Hp by 3% for every 1000 ft, so you can't turn as much pitch.

In reading this I wondered if the 89 was fuel injected or or does it have a carburetor......was wondering if you may have to re-adjust the carb for the difference in altitude....I don't know the answer to that question but it was something that popped into my mind. I would think if it's fuel injected, the computer would be able to adjust for the reduction in oxygen...but a carb wouldn't...just throwing that out for discussion.