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how to choose the correct prop. for optimum speed

TheBrain

Regular Contributor
Is it safe to overprop a vessel for speed?

My 22’ pocket cruisers hull is 1900LBs ½ way loaded, w/ a engine pod setback 20”. Original engine was a 165 merc inboard out board 715LBs.

Engine swapped is a 2004 johnson 175HP.carbed 2 stroke 383LBs pod and brace90LBs w/ 14.25x 24 stainless steel prop I went 53MPH on GPS it got a tad unstable.

It was suggested to me not to use a high pitched 24 never got a full explanation why.

I’ve dropped the pitch down to 19” same diameter and do notice a drop off in speed but quicker hole shot.

Then tried a 14.25x21 aluminum slower than the 24 haven’t clocked speed yet but livable

So Is it safe to over prop a vessel for speed?or doe’s this over stress the engine?considering a 14.5x22 aluminum.


Thanks for advice.
 
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I'm still confused certainly don't want to ruin the pistons. is this caused by constant WOT runs?

the boats engine w/ the 24pitch came off a bass boat that hull weights 1500LBs only 400LBs less than my cruiser.is it weight related plus shape of hull like the cruiser wasn't intended on blazing speed like bass boats are.
 
Ayuh,..... If the motor can't make the recommended rpms at Wot, it's lugging,.....

It's lugging All the time,..... at All rpm levels,....

Luggin' the motor causes excess cylinder heat, 'n detonation, which burns holes through piston crowns,.....
 
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