engine compatibility with mc1 outdrive

[thestigmach1]

I'm basing the hp estimate off the fuel injected 1957 that made 283hp. I may not quite make it but I should be able to get close. The heads are what is already on a motor I'm interested in, and I've seen the setup on a dyno on YouTube. Of course they may just be saying that's what it had, but it ran quite well. I'm basing the bell housing and flywheel of the fact that when you go to order a flywheel it's the same in general for a sbc, and my uncle says it's all the same as well. He built chevys for a long time. A lot of people say a well built 283 is better than a 350 for high rpms applications because it can rev higher for longer periods of time without adverse effects. And of course in a boat it's revved fairly high for long periods of time.

 

[Bondo]

A lot of people say a well built 283 is better than a 350 for high rpms applications because it can rev higher for longer periods of time without adverse effects.

Ayuh,.... If yer talkin' 'bout spinnin' it to 9 grand, Maybe,......

But, in a boat, yer lookin' at a 5 grand redline anyways,...

Btw,... What pitch prop is the I6 runnin' to get the right rpms,..??

 

[thestigmach1]

I'm not sure on the prop, it was on the boat when I bought it. Even if I don't do an engine swap it needs a prop badly because it's damaged a fair bit. I'm thinking it's a 19 pitch though. I know as I go up in hp I'll have to change my prop pitch other wise I'll just over rev it and not get any more speed or hole shot out of it. That's going to be largely trial and error since I won't have a set hp rating like with the stock setup. Unless I dyno the motor, which I probably won't do. As far as recline goes I like the idea of having something that is capable of 9 grand without blowing up and running it at 5000. Leaves a lot of buffer.

 

[Bondo]

since I won't have a set hp rating like with the stock setup

Ayuh,... If the prop is a 19", ya only have the choices of, 21", or 23", as that's 'bout as big as standard available props get, which is still gonna be Way small,...

'n a motor capable of spinnin' 9 grand, will have zero power at idle to 5 grand,....

The reason everybody runs a 350 is they're cheaper to build, 'n provide more Torque, which is what pushes yer boat,....

 

[thumpar]

The 283hp is probably from a pretty wild cam which can cause reversion in a boat. That is why you see the mild HP ratings on marine engines. You can't do a tone to hot rod them without causing problems.

 

[Scott Danforth]

I just sold my 320ish hp 350. it was vortec heads, Comp Cams XM268 cam and roller rockers, running a dual plane intake and a holley 750CFM carb. I was running 14 degree BTDC with 24 degrees advance (36 degree total) and 91+ octane

I kept the carb for my next build. the new owner is happy as a dog with a bone. Motor made great power up to 5200 RPM then the cam fell on its face (and I have a pig of a boat for the motor)

No way would I run the cam that was in the old 283's. that was a solid lifter, high duration / high overlap cam (read that as sucking the water up the exhaust into the cylinders) to run a cam like that, you need dry exhaust (such as jet boat headers) Also, that motor was a very high compression compared to a boat motor.

BTW, you can take a junkyard 1996-2000 SBC Block, add $300 worth of machining and balancing, $800 stroker rotating assembly, a new set of vortec heads and build yourself a 383 putting out about 350hp at the prop for about $2k total that will run on 87 octane all day long.

If I was in your shoes personally, I would locate a 292 cubic inch inline 6, change the cam to an RV/Towing cam - bolt it in and be running in a week. the 292 has so much more torque than the 283 your dreaming of. you can get low mileage 292's from old county trucks, old bread trucks, etc. and all the marine stuff from your 250 cubic inch will bolt onto it.

 

[thestigmach1]

I'd leave the 250 and build it up if anything compared to putting a 292 in it. Stock for stock there's only a few hp and torque gain, which could be achieved with my engine and some love. I did not know that the cam on the 283 would cause it to suck the water into the cylinders though. What cam would I have to switch in to make that not happen?

 

[Captain Ollie West]

If you really want something different, cobble together a junkyard turbo setup for you 250 :rockon:

 

[Scott Danforth]

If you really want something different, cobble together a junkyard turbo setup for you 250 :rockon:

make sure the manifold and turbo are water cooled marine rated. otherwise a very hot turbo in an engine compartment is like a lit match in a gunpowder factory.

 

[Bondo]

I'd leave the 250 and build it up if anything compared to putting a 292 in it. Stock for stock there's only a few hp and torque gain, which could be achieved with my engine and some love. I did not know that the cam on the 283 would cause it to suck the water into the cylinders though. What cam would I have to switch in to make that not happen?

Ayuh,.... The 292 has a Much longer stroke than the 250,..That makes for much more Torque, which moves yer boat,....

Hot Roddin' the 250, might increase it's horsepower, at the expense of down low torque,....

Changin' the cam in the 283 will lower the torque available, 'n move the peak horsepower lower in the rpm band,....
The 283 just don't have the stroke or displacement to be a real powerful boat motor,.... No Torque,...

 

[Scott Danforth]

If you havent figured it out, boats need torque. unlike a car motor, a boat motor is more like a tow truck motor, towing a motor home up a hill while in sand and stuck in high gear.

Unlike the 250 cubic inch which was a car motor turned into truck and boat duty, the 292 was built to be a tow truck motor, and has more torque 2000 RPM and below than any production small block V8 with the recent exception of the LS series. it also is limited by hits head design to 5200 RPM and below which makes it a great motor for boat application. it is a long stroke motor

The passenger side motor mount is the only obstacle on using a 292, and you can buy a fabricated mount to fix that issue.

regarding your cam question, you need to limit it to about 268 degrees of total duration (about 226 degrees or less at 0.050" lift) put that cam in a 283 like Bondo pointed out, and the 283 falls on its face. the 283 was designed to be a high RPM motor, not a low RPM lugger. the bore to stroke ratio is off, and the cam to make it work is all wrong for boat use. a 305 out of your grandmas mid 80's malibu would be a better boat motor than the 283