what pitch prop r u running on your 18' donzi with a 350 sbc?

[ratman]

i just bought a 71 18" donzi with a merc 350ci chevy with an alpha drive i currently have a 19 pitch that hits the 4800 rpm rev limiter easily, so want to put more prop on it i will also be reviing the motor 5700 to 6k rpm. was wondering what rpm drive and prop you guys with 18's are running. thx, rm

[Sam]

5700 to 6k rpm ? Quite frankly I don't think your 350/Alpha combo will have the ponies to spin any decent size prop at those RPM numbers. As for the Alpha running 5700 to 6k they were never designed for that kind of abuse. Even if you could get your nummbers up there I wouldn't plan on keeping your drive in one piece for long. If it were me I would be be looking to keep the rpms in the 5000-5200 range. It's a pretty safe range for the motor and drive.

Most of the guys that I know running 350's in 16's and 18's are running props from 22" to 25". There are no short cuts when it comes to prop slection. So you just have to bite the bullet and test, test, and test. There have been lot's of posts on the subject, do a search.

Good Luck
Sam ;)

[RedDog]

To get the RPM you want, sounds like you need less prop rather than more prop.

[BUIZILLA]

why did you want to over spin the engine by 1,000 rpm?? doesn't make any sense to me...

JH

[RedDog]

why did you want to over spin the engine by 1,000 rpm?? doesn't make any sense to me...
JH
Bui - you're sounding like an old fogey with that question :wink:
- http://www.donzi.net/forums/showpost.php?p=361136&postcount=21

[ratman]

i built a bunch of sbc's for off road, 44" tires and deep mud put a marine style load on the eng. my 350's id turn 8500 rpm my 383 7500 rpms never a problem, i ran full roller valve train and arp bolts in oem pink rods. the volvo 270 on our 76 never had any issue turning 5800 rpms for years and years with no issues. is the alpha a pos compared to the volvo drives? thx, rm

[Lenny]

5400 with an Ultra 24". About 150 hours now. No problems. I usually run about 3800-4000 for long periods. (over 1/2 an hour)

[dick grande]

i built a bunch of sbc's for off road, 44" tires and deep mud put a marine style load on the eng. my 350's id turn 8500 rpm my 383 7500 rpms never a problem, i ran full roller valve train and arp bolts in oem pink rods. the volvo 270 on our 76 never had any issue turning 5800 rpms for years and years with no issues. is the alpha a pos compared to the volvo drives? thx, rm

man that's so sweet. those pink rods are da bomb aren't they I bet if you freeze them theyd twist 10g for sure! lots better than that squished steel crap, i think they call it pm or something they're tossin out today. i can't get my baha faster than 6400 because it starts to miss, once last year it really ran rough and like shut off on me and stuff. merkruiser **** is the cats ass to dude, i've never hurt my alfa i run royal purple and amsoil 50-50 works great... that volva stuff is old teknology thats why you cant hardly by parts for them.