Cracked block. OMC Interchange question

[ciera sunbridge]

Hi I'm new here but have been lurking for some time and figured this is the best site to help me get a few very important questions answered. You all know yoru stuff

So long story short... I have a cracked block in my 87 OMC 3.0 cobra.

What year(S) engine will be a direct replacement. I just bought and towed home a 85 Sea sprite with what I Was told was a 3.0 cobra just to find out it was not and its a 3.0 stringer.

They sure dont look the same either now when I put them side by side. Trim is different not to mention I dont seem to see a bellhousing like on the 85 stringer nor does my engine mount to the floors stringers like the 85.

Right off the bat when I got home I noticed a few different things... On the 85 I just pulled home the engine mounts are completey different. Maybe this is not a big deal or is it? Can they be swapped out? Example.. the 85 3.0 is mounted into the stringers and mine is not and in he rear I have a transome plate that my motor is affixed to via mounts while it looks lik ethe 85 is mounted to a bell housing. Please correct me if I'm wrong though!

Another thing I noticed is that the front trim assembly are not the same at all. Qwick fit or deal breaker?



Note.... you can tell in the pictures that my engine was fairly new. Only 120 140 hours if I recall before she was Mis treated and sustained a block crack. Again this was not me but someone who I had winterize it and didnt. Thats a subject for another time though.

Here is mine and here is the 85... and yes I have water in my oil so welding the block is a no go. LMK what you all think. can I use just the 85 block since it dont look like I can just drop this dressed engine in?

My motor thats cracked....

Another of my Motor...

*******************************************************
The 85 I just yanked home... Note the different mounts.

Seems to be different layout then mine.

This is the what I think to be a Stringer not a cobra right? This is the 85 donor boat not my 87 of course.

 

[ciera sunbridge]

Re: Cracked block. OMC Interchange question

Few more pictures...
Crack in my block:-(

Mine...

The one I just bought yesterday...

 

[ciera sunbridge]

Re: Cracked block. OMC Interchange question

All you are exchanging is the block right?

Well I was not planning on just doing that. I was hoping to drop in the full dressed engine but that dont seem to be possible from my way of looking at it. However... If I had someone tell me that I can just strip the 85 3.0 and swap over all my new goodies and that it would be a direct fitment... then yes I would go that route.

 

[solar7647]

Re: Cracked block. OMC Interchange question

If they are the same block, just strip the new one down to the block and then rebuild it using the parts from your original motor, head, manifolds hoses ext. They should bolt right on. You will just need to get a new gasket set.

Then take all the parts that you arnt using from the Stringer and sell them on ebay!

 

[solar7647]

Re: Cracked block. OMC Interchange question

Well I was not planning on just doing that. I was hoping to drop in the full dressed engine but that dont seem to be possible from my way of looking at it. However... If I had someone tell me that I can just strip the 85 3.0 and swap over all my new goodies and that it would be a direct fitment... then yes I would go that route.

I would think you could you will just have to transfer everything including the drive.

But I would just rebuild using the block from the one you just got. It will be less head ach. Just MO

 

[ciera sunbridge]

Re: Cracked block. OMC Interchange question

Solar...

Check out this pictures I found of a 3.0 NON cobra.

Notice the engine mount I dont have these and the trim is way different setup. I would hate to take evrything off just to find out things wont bolt up.

 

[solar7647]

Re: Cracked block. OMC Interchange question

Solar...

Check out this pictures I found of a 3.0 NON cobra.

Notice the engine mount I dont have these and the trim is way different setup. I would hate to take evrything off just to find out things wont bolt up.

That engine isnt stripped to the block. You want it to look like this.

According to the site where i got this photo this is the replacment block for both of the engines you have. So they should be able to be swapped. The mounts from your Cobra should bolt on the other block.

 

[solar7647]

Re: Cracked block. OMC Interchange question

I dont have a lot of OMC knowledge but this should all unbolt from the block at the location the red arrow points to and all that stuff should come off.

 

[ciera sunbridge]

Re: Cracked block. OMC Interchange question

Thanks Solar. As you can tell.. I'm not to well educated on wrenching on boats. My Guess was that the blocks were the same I was just worried that there might be some differences.

Guessing I would now strip the 85 down to just the head and block right? Considering my current head will have watery oil running through it.

Man this is going to be alot of work all for a 3.0 that should have never been put in my Sunbridge. Bayliner under powered many of them to pass on the savings to boat buyers. I have seen many more 5.0 in my 2150 then 3.0s.

I'm almost considering ditching this all together and looking for a V8 donor boat for a full swap. Thoughts? Sure would be nice to get out ofthe hole faster and not have to be 5000 RPM to plan out all the time.

 

[solar7647]

Re: Cracked block. OMC Interchange question

Considering you have the space and the transom is good you could swap up, but considering your lack of wrenching know how it may be a bad choice, plus you will prob have to do some wood and fiberglass work because V8's mount on the sides of the engine.

Yes you need to take everything of the Stringer so you just have the core block with the and the head. Then as you remove thing from the cobra you put them on the other block.
You will need a overhaul gasket kit for the Cobra. they run between $100-200.
You will also need a manual for the Cobra if you dont have one.

My signature has a link to my 3.7L rebuild, the parts and make of the motor are different then yours but it will give you a good idea of what you have to do.

 

[bruceb58]

Re: Cracked block. OMC Interchange question

Before you go through all the trouble of putting this other engine in your boat, I would consider starting it up first and measuring the compression. You can do this in the old boat you have. You just have to supply water to the engine and probably run it from a portable tank if the fuel is unknown.

 

[solar7647]

Re: Cracked block. OMC Interchange question

Before you go through all the trouble of putting this other engine in your boat, I would consider starting it up first and measuring the compression. You can do this in the old boat you have. You just have to supply water to the engine and probably run it from a portable tank if the fuel is unknown.

Good point!!!!! this slipped my mind, no sense in doing it only to find the new block needs work to!

 

[ciera sunbridge]

Re: Cracked block. OMC Interchange question

Thanks guys... I did a compression test on it before i bought. It was about 120 across all 4. So the rings are not shot by any means. It was holding 30 PSI at idle per the gauge on the cluster as well but I wasnt going by that of course.

As far as experienced.. yes I lack working on boat engines in general. However.. I use to be ASE certified back in the day and also have 20 years racing and many years budiling Ford engines for my my drag cars. So swaping over and being a parts changer on this type of project would be easy for me.

I was just concered about the over all casting design and or mount locations. maybe some there maybe some not etc.. Thats why I was really looking for a dead YES on the swap. After all this... I think I'm just going to put a v8 Mill in. Bayliner installed many of the 2150 Cieras with v8's So my guess is everything is there ready for a V8. It wont be to bad if I have a complete donor boat side by side.

Solar.. I looked at your project a few posts ago. Looks real nice!


Thansk for everyones help on this.

 

[solar7647]

Re: Cracked block. OMC Interchange question

Good luck with the swap.....Since you are going to do a hole swap with a V8...get something other then OMC...considering they are no longer in Buisness and you will need to change drive anyways.