Too Slow: Aquacraft 22-2 Osprey CC INBOARD

[Larryowen]

Man, am I glad I found you folks. Being a 77 yo lifetime Florida boater and previous Aquasport owner (3). I need some advice because I am holding the tail of a monster I'm in love with.

I recently purchased a 1977 Aquasport 22-2 Osprey INBOARD ... always wanted one.  It's in terrific shape, most likely refurbished a couple of years ago. My dilemma is finding out why it will reach only 18 MPH at 3800 rpms and maybe 19-20 mph at 4500 top end.  It has a 350 Chevy which has been "marinized" according to the  guy I bought it from. He said 300 HP, but good luck! Don't know what the HP is. It runs fine, idles fine. I replaced the Holley 4bbl and the point-style distributor with a single-wire DUI distributor, complete tune up with all new parts ...and still the same 18MPH @ 3800 rpms.  The engine seems to have good torque; comes to plane quick enough.

The boat had a full, dual-control tower and getting up and down was a dangerous feat for me , so I removed it thinking I'd lose the weight and wind resistance and thus go faster. Nope!  Even lighter, still only 18 mph.

I'm thinking it could be either the engine is not powerful enough, or it has the wrong gear and/or prop setup. Please halp!  I love this boat but I must get from the Manatee River to the Gulf in less time!

If I need to post this somewhere else, please advise.

[theFunsmith]

There are many on here that know more than me, but the size and pitch of the prop would be good information to add. I have a hunch that it may be the culprit.

[Capt. Bob]

I believe these are the factory specs.

https://classicaquasport.com/smf/index.php?topic=14342.0

Tip of the hat to Funsmith.


Light reading:

https://classicaquasport.com/smf/index.php?topic=6417.msg45553#msg45553

Tip of the hat to Fitz.

Good luck.

[GoneFission]

A 350 marine 4 bbl carb engine usually puts out 250-270 HP and that's plenty for the 222.  Is it direct drive or is there a reduction gear in the transmission?  Props would be different depending on gear ratio.  You should be running around 40 at 4000 RPM with a 2:1 ratio and a about a 14x19 prop.  If it's direct drive (1:1 ratio) the prop pitch would be much less - maybe a 14x13.  Direct 1:1 drive would not be my preference on that setup, as the tip speeds on the prop at 4000 RPM are likely to cause cavitation and slip will be high.  The size and pitch should be stamped on the prop hub.  See what you have.  I would guess you will need to increase pitch a good deal. 

One more question - do you know the condition of the foam under the decks?  Have you weighed the boat?  How does she sit in the water?  Some of these boats have wet foam with hundreds of pounds of water under the decks.  That can affect performance a lot! 

[Larryowen]

Thank you to all of you ... I'll get the prop numbers tomorrow, and investigate the transmission/drive type. I'm starting to have confidence we'll get the craft running right based on the sage advice and info. Again, thanks!

[theFunsmith]

I believe these are the factory specs.

https://classicaquasport.com/smf/index.php?topic=14342.0

Tip of the hat to Funsmith.


Good luck.

Should you find you need a different prop, I still have those two props listed there as well. They came with (and on) my 22-2 before I went at it.