Volvo Penta 275 - Max HP Rating

[JRS85]

I was curious as to what the maximum horsepower a 275 outdrive can handle. The boat originally came with a 305 (225E, I believe) and has been upgraded to a 350. I do not know any of the specs for the motor other than 5.7 is stamped on the block.

When I have 5 or 6 people in the boat, the time to plane is pretty slow. The boat has a cuddy and all of the weight is in the rear. I have access to an aluminum intake and heads that I can interchange pretty quickly, but I want to be sure that I do not exceed the maximum hp rating.

Any help would be greatly appreciated. Thank you in advance.

 

[Howard Sterndrive]

Re: Volvo Penta 275 - Max HP Rating

exhaust restriction would be my only concern. The drive can handle the power, but the 275 might restrict the exhaust too much unless you convert to through hull exhaust.

 

[Don S]

Re: Volvo Penta 275 - Max HP Rating

The drive will take it, but if you want it to get out of the hole quicker with a load, find a DuoProp lower unit and props. Then it won't be as slow getting on plane.
But any single engine boat will be sluggish with 5 or 6 people on the back when you are trying to get on plane. What sze boat is it?

 

[JRS85]

Re: Volvo Penta 275 - Max HP Rating

Thru hull exhaust is installed, so restriction shouldn't be an issue. The boat is 23'.

As far as the duo prop unit, is this a direct swap and is the associated cost worth the effort? Will swapping the heads and intake make any noticeable difference? I have access to a set of older 462 double hump SBC heads as well as some others.

Any opinions welcome. Thank you.

 

[Don S]

Re: Volvo Penta 275 - Max HP Rating

The 27 Bayliner Victoria I had would do about 17 at WOT with the single prop. Went to DP and it went 30.
At 3200 rpm I was doing about 20 or 22 and didn't have the secondaries open. Stock old style chevy 5.7 with a Qjet carb.
Still got on step quickly with 4 adults on the aft deck and 2 on the flybridge.

 

[JRS85]

Re: Volvo Penta 275 - Max HP Rating

My engine setup is pretty similar. The boat is a Baretta 230 Phaser with the old style 350. I have replaced the QJet with a Holley. Have no idea as to the specs on the cam or heads.

That's a pretty impressive jump in top speed by going to the duo-prop. I think this might be the route I need to go.

Also, is there a specific duo prop lower that I should look for?

Thank you very much for your fast responses.

 

[Don S]

Re: Volvo Penta 275 - Max HP Rating

You want a 290 style lower unit with a 1.95:1 gear ratio.