Volvo Outdrive Ratings (Motor HP Limits)

[Rick]

I am building 351Ws that will meet with Holman Moody outdrives (AKA Volvo 250s)When the outdrives were rebushed the guy that had the parts said don't push more than 350 hp through them some parts are unavailable. The question is what is the torque or at what RPM? When I Dyno my motors I can do what I Want. Is this 350 hp at 4500rpm 5500rpm? Is there a rule of thumb? Does it even matter if I don't blast it out of the hole? I would guess that my reduction is 1.5:1 being the original drives and motors. I am in the gearbox business and none ones outrives would work if they received half the torque these motors produced at RPM. Not to get too sidelined. Can anyone help me out?

[boldts]

Rick,
Past experience with a Volvo 250 drive on an 18' Classic with a 302 Ford in front of it. The drives gear ratio should be a 1.61:1, not the 1.5:1 as you stated. I blew the upper gears by hitting a submerged obsticle and when rebuilt, had no problems with the drive in the next 16 years of ownership. Of course, take this with a grain of salt because I was not running a Hypo engine in front of it. How-ever, I was always told you can run as many RPM's through the 250 as you want, just don't try to put a lot of torque through the drive. So, small dia. props with more pitch is the ticket. Ran a 14 x 22" on mine at 4950 with a speed of only 48 MPH. Really didn't play with props, but I've also been told that speed is greater if the drive trim is run in the second hole rather than the third hole from the transom. Hope this helps a little! :)

[Gearhead99]

Use to run a 351W with 350HP[engine dyno'd] through my 250 Volvo without any problem. BUT, when I added a 175 HP NOS hit. Well the drive came apart VERY soon after. The lower foot exploded and ruined the housing.

Changed to a 270 Volvo drive that was adapted to take Merc props. Then ran a cleaver. Never had any problems again.

[Rick]

Dave, at what RPM was your 351W rated at 350HP? Thanks Rick

[DON N.]

Seems in the volvo days that the donzi's with 400 hp and up were all shaft drives. Look under old ads on registry.

[MOP]

Boldts I am surprised you blew an upper hitting a log. I was a Volvo tech for many years, one of the films they use to show at school was the drive hitting telephone poles st high speed with no damage. Usualy the shear coupling goes if anything. I think they are a very tough drive, I want to get my hands on an XS. I also feel if you are going to put power to any drive no matter whos, tear it down inspect it and re shim it give it the benefit of good close tolorences.

[Gearhead99]

If I remember correctly the dyno pull was to 5200 rpm at 350 HP. Above that was marginal. I would prop the boat to do 4700-4800 WOT dry [military] power. When you hit the NOS it came on and would bump it up to 5700 or so. Motor was built WELL. Had forged 9 to 1 pistons, balanced, solid roller lifter, roller rockers, 7/16" studs, windage pan, 10 qt oil, MSD, major ported cylinder heads, Chevy valves and either a 750 Holley or AFB. I prefered the AFB. No darn power valves to keep blowing out.

Am in the process of building a stroked 351W. Going to be 426W when I'm finished. Nothing to put it in right know. Was building it for my 68 Mustang.....but, I'm not sure I'm going to install it in it.

[tmdog]

Built a killer motor for my 18 Classic. Chev. 350 pushing in excess of 500 h.p. with a Volvo 270. Only problem was getting into gear at the erratic idle, broke verticle shaft 3 times. Found the answer, start the engine in gear.Ran a special 26" prop. Never ran it up to top speed, scared the hell out of me.

[Rick]

Gearhead thats pretty wild my motors are forged flat top, chevy valved (manley stainless) solid roller motors with holley 750 double pumpers, heads ported more for torque than high volume air. Hamburger oil pans, rear oil pickups, ARP rod and head bolts. Small world. Will let you know what they Dyno out. Hoping for mid 300's at 5500rpm. Would like to prop it at peak HP. Do plan to stay off the bottle though. I am more interested in sorting the whole rig out. How will you accomplish your stroker?

[Rick]

Tmdog, my guy told me whatever I do make the engines idle at 650RPM or below or I will blow the top of the drives off when I shift into gear. So my plan is to have a slow idle and decent upper end hp. Will let you know if it can be done.

[Moody Blu']

I have about 340hp in my 351w and i push my volvo 250 hard and it never blinks. just make sure the universals are in good shape, and if your not sure just replace them....

I know BZMARINE(donzi.net member hasnt been around leately though) has a stroked 401 351w and hes pushing 80+ mph with a 33PITCH (no joke) prop from spinelli. that motor has over 500 HP (ok maybe 450hp?) and his drive is fine.

Big griz says those drives are stronger then bravos, as long as you dont rev the drive past 5200-5500 rpms, that goes DOUBLE for the 351w, the valve train cant handle the high rpms, unless youhave it built for high revving, (thats my next project)- all ford motorsport rockers with a 1.7 ratio and tight ass springs....

hey griz why dont you throw a wrench in here....

[Rick]

Thanks for the info.....Rick