'79 OMC GM: Can I drop in any old 305/350? How about a Ford 302/351?

[gallipoli]

I have an OMC Setup with an 800 series stringer out drive (works) but the engine flooded with salt water and seized from Hurricane Katrina. It is an OMC GM 230 HP V8 '79 or '82 305 cid or 351. The boat is a 1979 John Allmand 23' with hard top.

I don't have time or money to assemble a new long block or have it professionaly rebuilt. I need a used motor drop-in solution even if it needs a little work.

Can I put just about any GM 305/350 setup on the same motor mounts? I'd like to avoid fiber glass work or structural redos of the transom or stringers. I was told any pre-'86 350 or 305 should bolt onto my intermediate housing and fit on my existing motor mounts. Is there anything else to it other than the obvious remove O/d and engine, drop in engine, wires, out drive and linkages, re-connect outdrive and boot? I'm looking at a couple boats with hull damage and running GM motors to swap cheap.

Option 2: I have a '77 Ford 302 engine and int. housing available (OMC 800 stringer outdrive removed). I know the intermediates will need swapping. They are the same rotation OMC 800 stringer series electric shift out drives. Will the Ford V8 engines fit on the GM V8's motor mounts? If the stringers are good is any fiber glassing necessary?

I can handle removing and bolting on carbs, heads, manifolds, int. housing, pumps, etc but I have no clue when it comes to fiber glassing or moving motor mounts and never swapped a motor.

Any help? At least my home had flood insurance (got 5 feet of water), the boat is lucky to get Sea Tow paid for. The budget is too small to get a rebuilt motor or do fiber work and since the hurricane all labor is 4 x the price!

Thanks in advance this board is awesome!

 

[gallipoli]

Re: '79 OMC GM: Can I drop in any old 305/350? How about a Ford 302/351?

Just to clarify, if I buy a 305 or 350 it would be a COMPLETE motor with accessories (alternator, starter, pumps, etc). I'm not going to buy a long block and try to reuse old parts. I'm reusing the outdrive and intermediate if it fits.

If my stringers work with a Chevy 305 will they fit a Ford 302 or 351? Is moving motor mounts easy? Is it safe to assume the mounts are the same distance apart from side to side? Does this apply to V6 also?

 

[AaronG]

Re: '79 OMC GM: Can I drop in any old 305/350? How about a Ford 302/351?

Yes, you can use a 305/350 from a junkyard. Just make sure it is the older 2 piece rear main design, I believe the later ones will require an adapter to fit.

You need to swap the starter, alternator, intake, carb and exhaust from your old motor. You also need a marine circulating pump, and brass freeze plugs.

I don't believe the Ford stuff will easily bolt up. Also, marine parts for Ford engines are more expensive than GM engines.

 

[WillyBWright]

Re: '79 OMC GM: Can I drop in any old 305/350? How about a Ford 302/351?

Nothing Ford will fit anything GM.

 

[gallipoli]

I want to swap out the entire setup

I want to swap out the entire setup

I know I'm making this more complicated than it is.

I am going to drop in a complete motor with bell housing, pulleys, belts, carb, manifolds, risers, etc... everything but the outdrive. I don't want to do any hull structural work (stringers or fiber glass).

My OMC 800 outdrive is fine and I'm getting ready to pull out the entire 305 to put another complete setup in.

I found a good running '77 Ford 302 V8 recently rebuilt ready to drop in with intermediate housing for $400.

I'm looking for OMC Chevy V8's ready to go but they're more expensive (at least $1,200 inc shipping).

Is it the same amount of work to get the engine installed with either motor?

Is it any less work to put in a Chevy since it fits on the same motor mounts and fits perfectly?

I can't reuse any old parts because they're all rusted red from salt water in Hurricane Katrina.

The kids want to go fishing, "are we there yet?"

 

[JackCoWo]

Re: '79 OMC GM: Can I drop in any old 305/350? How about a Ford 302/351?

i don't see why swaping brand engines would make a job more difficult, as long as the ford engine is complete, and you have the ford int. housing. But the nice thing about the chevy engine is parts availbilty. I would also doubt that you would have to do major structual work to the boat. in 79 OMC offered chevy 305, 350, and the ford 351, which shares the same bottom end diamentions as the ford 302. And I would assume most boat builders would have build the boat with that in mind. But finding a good used chevy small block engine shouldn't be a hard or expensive proposition either.
But BRP has a nice parts break downs to guide you what kind of parts you are looking at for the engine change.
http://epc.brp.com/login.aspx?Retur...ealerlocator=no&AspxAutoDetectCookieSupport=1

 

[Don S]

Re: '79 OMC GM: Can I drop in any old 305/350? How about a Ford 302/351?

Fastpony, read WillyBWrites post again. Ford is not like a Chevy. While OMC, and even Mercruiser and Volvo used engines from both Ford and Chevy, the parts were not interchangable.

 

[JackCoWo]

Re: '79 OMC GM: Can I drop in any old 305/350? How about a Ford 302/351?

Cool Don, which parts are you refering to, that i claimed were interchable?. Are you implying that OMC, Merc, Volvo used completely different drives for the different engines?, thats the hundreds of boat mfg. produced a different boat for the customer's choice of engine?

 

[Bondo]

Re: '79 OMC GM: Can I drop in any old 305/350? How about a Ford 302/351?

Are you implying that OMC, Merc, Volvo used completely different drives for the different engines?, thats the hundreds of boat mfg. produced a different boat for the customer's choice of engine?

Ayuh,........... That's pretty much the Way it Works............

 

[gallipoli]

Anything will drop in as long as the right intermediate is used

Anything will drop in as long as the right intermediate is used

Now I see it's common sense that the stringers should support any type of motor. It's not like you have to buy a different boat because you're upgrading the V6 to a V8.

Two of my buddies who have done the engine swap operation said I should be able to put a V6 or V8, Ford or Chevy and it won't matter as long as I get the appropriate intermediate housing.

Any of them should fit on my stringers easily. If I put a V6 or a Ford V8 I might have to move the mounts forward or back a few inches and use the respective mounts.

I guess that pretty much wraps it up so I'll go find whatever motor I can that had an OMC 800 on it.

Has anyone tried to put a Mercruiser GM V8 engine to replace a OMC GM Engine?

Is the only different the intermediate housing and exhaust manifolds? I could re-use them.

 

[Don S]

Re: '79 OMC GM: Can I drop in any old 305/350? How about a Ford 302/351?

Those that don't know for sure, always say it's easy because they don't know any better.
Get your "buddies that know" together and make the change. It's just that simple.

 

[paulie0735]

Re: '79 OMC GM: Can I drop in any old 305/350? How about a Ford 302/351?

yeah, no problem......... should take you and your buddies about 45 minutes. That will leave the rest of the weekend to sit around and scratch ya head trying to figure out why nothing fits!

 

[WillyBWright]

Re: '79 OMC GM: Can I drop in any old 305/350? How about a Ford 302/351?

Intake and exhaust manifolds are different. Carbs mount the same. Then there's the mounts for the power steering and alternator. Bell housing is different and possibly even the coupler that bolts onto the flywheel. And of course the flywheels are different. Different starter and probably more. DO NOT use automotive carburetor, starter, alternator, or distributor. We call boats like that Widow Makers.

 

[gallipoli]

Are Ford and GM V6 and V8 engines a standard width at the engine mounts?

Are Ford and GM V6 and V8 engines a standard width at the engine mounts?

Thanks for telling me which parts are compatible your information is quite useful.

These comments below aren't directed to you but
My question was are the Ford and GM V6 and V8 engines all a standard width at the engine mounts?

I gave too much information and only one person really addressed the question.

It doesn't matter what parts will fit because I'll have a complete setup including bell housing and intermediate housing to fit my OMC 800. I'm 100% sure the intermediate/bell housing and outdrive will bolt up.

I had no clue about the motor mounts.

I'm not re-using any parts except the outdrive itself. I'm buying a complete drop-in; everything from carb. to exhaust to bell housing/intermediate housing, pumps, belts, alternator etc and and motor mounts. It doesn't matter if the exhaust is different or V6's have a different gear ratio; I find a drop-in engine then I'll address outdrive gearing.

Thanks for you help; if anybody else has measured or knows if Ford and GM V6 and V8 motor mounts are the same width let me know (the distance between mounts port to starboard). My stringers are 4" wide and I'm guessing 20" apart (I will measure this weekend).

 

[gallipoli]

Last question: Can I drop in a Merc GM V8?

Last question: Can I drop in a Merc GM V8?

Thank you all for your responses. This topic was alien to me at the start and is becoming a reality.

Question: Will an OMC intermediate housing for GM 305 fit on a Mercruiser GM 305/350?

I see a lot of complete Merc 260's available (GM V8) which are less $$$ than OMC complete engines. I was told to look for a two-piece rear seal (pre-'86).

Common sense says the GM 350 Block on the Merc is the same as a GM 350 block on an OMC. I'll re-use the exhaust manifolds and intermediate housing from my Chevy 305 OMC.

Other than "nothing Merc will fit OMC" which is B.S is this conversion easy or not possible, and why?

I found more Mercruiser engines complete and running and for less than complete running OMC engines.

 

[lilmandavis]

Re: '79 OMC GM: Can I drop in any old 305/350? How about a Ford 302/351?

jut make sure you get a gm coupler for the gm or a ford coupler for the ford. the only interchangeable parts between the two would be the carb and the older dana 60 axles. which ummm arent on a boat.