Over-propped?

[SEGAangler]

First off I apologize if I'm posting this in the wrong place. I've got a 19 ft Bayliner that I'd estimate around 2700 lbs loaded. It's powered by a 140 HP Evinrude. The motor was original (actual gear ratio unknown) and performed well with a 13 3/8 x 17 prop. After a lower unit failure it was outfitted with a V6 gearcase (actual gear ratio unknown). This unit came with a 14 1/2 x 19 prop. I haven't been able to water test it yet. Is this going to be too much prop? I'm not concerned with hole shot or top end either; I just want a decent ride w/o straining/stressing the engine. I know many people argue pros and con's regarding that gearcase change; but it's done and my hopes would be to get 2 seasons from it. Any input on prop suggestions or things to watch for is appreciated.

 

[alldodge]

First off I apologize if I'm posting this in the wrong place. I've got a 19 ft Bayliner that I'd estimate around 2700 lbs loaded. It's powered by a 140 HP Evinrude. The motor was original (actual gear ratio unknown) and performed well with a 13 3/8 x 17 prop. After a lower unit failure it was outfitted with a V6 gearcase (actual gear ratio unknown). This unit came with a 14 1/2 x 19 prop. I haven't been able to water test it yet. Is this going to be too much prop? I'm not concerned with hole shot or top end either; I just want a decent ride w/o straining/stressing the engine. I know many people argue pros and con's regarding that gearcase change; but it's done and my hopes would be to get 2 seasons from it. Any input on prop suggestions or things to watch for is appreciated.

This is he right section, your talking props.
You have the right prop if you can reach WOT RPM range with the boat loaded like you normally use it. We can find out what your WOT range should be but not knowing if you were reaching it prior is an issue. Also unknown previous drive ratio is a biggy. You could figure out the current ratio by turning over the engine by hand in gear and counting rotations. There just to many pieces missing to be able to determine what would be best. If it was mine I would start with the old 17 pitch prop and take the other with. Give it a try and give us some numbers and we can help more

 

[SEGAangler]

I'll have to try with the new prop; the old 17 is for the smaller V4 gearcase. I hope to get it out in the water to try this week.

 

[steelespike]

I think the ratio is the same but the 14 1/2 X 19 will probably slow things. And make the 140 struggle.
Get us the lightly loaded wot rpm and gps speed and we should be able to help.

 

[SEGAangler]

By GPS speed of 44 mph I was (theoretically) running around 5500 RPMs on the old setup which it seems was 2:1 gears. The new gear is 1.85:1. A little deeper research gave me these ratios and the calculation was: SPEED= [RPM?Gear Ratio] X [Pitch?1056].....All things considered I do believe the 19 is going to be too much. I will run it and get the WOT rpms and speed, hopefully tomorrow afternoon or Thursday, and maybe we can narrow down the size before spending $$ on a new prop. Thanks guys; as soon as I can run it I'll post results

 

[SkiDad]

i would agree that 17 is probably going to be what you need. I can't see you hitting 44 with a 17 unless you are running about 6000 - but I think that might be ok for that engine.

 

[SEGAangler]

I'm honestly not concerned if I hit the same top speed or not; my main concern is not over-stressing the engine with too big a prop. Mitzysman, it seems I have an identical boat to yours....so as you're aware my motor is actually over the boat's rating!

 

[SkiDad]

what year ? mine is a 1985 but rated for 140... they really should have rated it for 150, but I think 140 was the largest Chrysler back then.

 

[SEGAangler]

'85 by hull number but somehow Ga DNR has it as an '86. Trophy 1910 rated at 130; came new with a 125 Force. When I got it it had the 140 Evinrude with 25" shaft on a jackplate. I rebuilt the transom at 25" and eliminated the jackplate to reduce rear end weight