Old School Volvo and HP limits

Mario L. · 10-03-2009, 09:30 AM

I'm restoring over the next few years a Magnum Marine with twin Volvo 250 drives. I will be keeping this boat original but with new engines.

Presently it has two 350 HP 350 cu in SB Chevies, and these need rebuilding or replacing. My plan is either 383 or 372 SBC built to get as much as I can from the boat, without altering the rear hatch, adding scoops, or blowers.

I have no idea who to believe, I've heard 600 HP is fine to a Volvo drive??? if the boat doesn't see air time and re-entry . . nearly impossible, and what fun is boating w/o air time???? Besides, 600 HP is way more than I can reliably get from 372-383 SBC that I need to have last 350-400 hours.

I just rebuilt the two drives, and have to say was very impressed with the lack of wear internally. Gears were all fine, bearings were fine except where moisture got to them. This was in the upper housings as the boat sat for 10+ years on a trailer close to a salt marsh with torn and deteriorated bellows.

Limits seam to be the prop selection for the standard Volvo drive. But what about prop selection for the old Speedmaster drives.??

You see my boat here:
http://www.offshoreonly.com/forums/m...ml#post2965434

Thanks for the help!

Throttle Fever · 10-03-2009, 11:25 PM

Ran 450 hp (406 small blocks) thru 280 volvos for 10 plus years with out a glitch. Also heard 600 was the limit on the 280's. My 280's had 1.61 ratio and I ran rehubed mirage 3 blades 25 pitch wheels. It was a 30 foot 7500 lb boat. Did regular maintenance and change the synthetic gear oil ever season. Never had a issue. Do not know about a 250 though. Thought they made a 270 and a 280. And they were very similar. My 2 cents.

tms1155 · 10-04-2009, 09:41 PM

280's were a little stronger than the 250 and 270 drives. they should still handle what your going to get with small blocks. Just pay attention when you go airborne. If you dont pull back fast enough you will hurt them with any HP.
You may also try switching the drives to spin out(only need to change cables around on drives and switch props) thats the way they were when the boat was made.

hallj · 10-05-2009, 01:32 PM

I liked the Solas props when I ran them on my Magnum!

Jeff