Expected speed and RPM

I recently purchased a used 1991 Valanti 220 XL. Specs are:

5.7L Mercruiser, 260 HP Alpha One
3700 lb dry, 60 gal fuel tank, 5-6 people on board
Prop: 14.5" diam, 19" pitch aluminum (new, same as old)
WOT RPM: ~4200
Max MPH: 35-38 (GPS)
Comes up on plane @ ~3000 rpm

Does this sound about right? I had assumed a 260 HP motor would do more than 38 mph, but never having owned a boat, I have no real basis for comparison.

Also, does that prop size sound about right for a boat of this size/weight? I know it's at the low end of the recommended WOT RPM range, but I wanted to see whether it's the prop, or the motor is not as strong as it should be.

FWIW, the motor looks and runs great - nice and smooth, no strange behavior. I'm just trying to see if I'm in the ballpark of "normal".

Any comments are welcome. Thanks!

Re: Expected speed and RPM

Animal223 said:

5.7L Mercruiser, 260 HP Alpha One
3700 lb dry, 60 gal fuel tank, 5-6 people on board
Prop: 14.5" diam, 19" pitch aluminum (new, same as old)
WOT RPM: ~4200
Max MPH: 35-38 (GPS)
Comes up on plane @ ~3000 rpm

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Looks like what I would expect to see. The bottom end of the WOT range is typically where the best performance comes from.

Re: Expected speed and RPM

I agree with RP, but I am curious about your use of trim. Can you tell us about how much positive (up or out) trim you are able to use? Are you trying different trim settings? Also, have you run her at all with just you and low fuel? I'd be curious about the RPM and speed increases from a light load as well.

P.S. Thanks for the great info to start with!

Re: Expected speed and RPM

I'd Think that a 350 in a 22' boat otta see the Low 40s.......With 30 gals. of Fuel,+ 1 or 2 people......

As QC mentions,.... There Might be another 3/5mph to be found in the Trim button.......The Other 600 rpms Might be there Too......................

Re: Expected speed and RPM

QC said:

I agree with RP, but I am curious about your use of trim. Can you tell us about how much positive (up or out) trim you are able to use? Are you trying different trim settings? Also, have you run her at all with just you and low fuel? I'd be curious about the RPM and speed increases from a light load as well.

P.S. Thanks for the great info to start with!

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If I remember correctly, my trim was about half way or maybe a little more out... I adjusted it until it seemed to have the optimal performance without cavitation. Other trim settings produced lower RPMs (~4000).

I'll try with a lighter fuel load with just me, and see what happens. Thanks for the input!

Re: Expected speed and RPM

Also, in case it helps, the drive has a Doel-Fin hydrofoil attached.

Re: Expected speed and RPM

Animal223 said:

Also, in case it helps, the drive has a Doel-Fin hydrofoil attached.

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Ahhhhhhhhh! Lose that thing and fast. Every test I have seen showed that they slow the boat down . . . Can cause other issues as well, but honestly may have solved a porpoising problem though too.

You may be able to get the bow up (trim out) further before ventialting if you shift some weight aft, but that will increase the tendency to porpoise. That can be managed with trim tabs, but let's see how she performs with that abomination off of the drive