motor / make swap

[Phantom17]

Hey all, I have 2 answers on this so I need to know what the pro's / experienced think. <br /><br />I have a 1981 OMC 2.5 litre 120 hp, 400 O/D. Runs excellent, bad drive.<br /><br />I want to replace a 1985 merc alpha 1 (probably 3.0) 140 hp with my OMC motor (both OMC and Merc are GM based engines). I have all the housings that came with each set-up. Is this an easy swap, and what I am looking to replace. I would think the motors are identical except the mounts, which I will swap off when both motors are out. <br /><br />Appreciate your help.-Jeff

 

[KaGee]

Re: motor / make swap

Let me see if I understand you correctly...<br /><br />You want to stick your motor in another boat??<br /><br />If so, I believe the answer is yes, GM made all those base blocks as far as I know yours should bolt up. However, you would have to swap everything else from the Mercruiser... wire harness, etc. Basically you would only swap the long block.

 

[rbezdon]

Re: motor / make swap

If you are talking about doing it the other way, switching the drive onto your boat and engine, I am pretty sure you will have to completely redo the transome cut out which is difficult. Fill in the old cutout and make a new one.

 

[Phantom17]

Re: motor / make swap

Keith has it right. I want to take my GM OMC 2.5 litre and put it in a different boat with a merc drive. The merc boat had a 3.0, with an alpha one, and I have about had it with the omc drive I have (400 stringer hydro). <br /><br />As far as the wiring goes Kieth, have you done anything like this? I don't want to get into another project right now. How about the motor mounts? Am I getting too deep doing this or is it basically simple.<br /><br />Just hoping to be able to either sell mine needing a lower, or keep my motor, part out everything else and sell the hull and trailer.

 

[rbezdon]

Re: motor / make swap

Just treat the project like a long block swap, Swap all the castiron stuff and use the old MErc stuff on the "new" block. Since the Chevy block is the same, everything should bolt right in.

 

[Bondo]

Re: motor / make swap

Like Ron says,........<br /><br />Just treat it as a "Long Block Swap",......<br />And Everything will Go Smoothly,...........<br /><br />Those blocks are the Same Casting on the Outsides...... All the Bolt Holes are in the Right Places............

 

[Phantom17]

Re: motor / make swap

Excuse my inexperiance, but when I pull the OMC motor, and swap over the mounts etc, will I only need be concerned with the inside of the boat? The drive has been in indoor storage for a year and a half, so it is already off. I bolt the motor down and then use an alignment tool to install the drive, or is there an alignment system for the motor as well? I obviously plan on getting the book, but I am still considering doing this purchase. Boat money is so thin it's scary, but I think I might have a decent deal here. The boat itself is 5 years newer, and I honestly don't want to put money into this 400. What am I looking at for his swap? I really appreciate your input gents.-Jeff

 

[Bondo]

Re: motor / make swap

Well,...............<br />Even though this is a SBC,... It'll give you an Idea of How Far you need to Disassemble the OMC to get down to the Long Block,...........<br />

<br /><br />Once you've Stripped the OMC,+ Reassembled the Motor with All the Mercruiser Stuff,........<br />Then you Install the Motor,+ Align the Motor to the Gimbel Bearing,..........<br />Then the Outdrive is Installed,+ Hopefully You Go Boating...........<br />

and I honestly don't want to put money into this 400.

I find it Hard to Believe that Anybody could argue That Point.................<br />

What am I looking at for his swap?

Just Make Sure,.. You get ALL of the Mercruiser Stuff..........<br />Little Parts will add up Fast.......

 

[rbezdon]

Re: motor / make swap

If as you say, the OMC engine is in good shape and the problem with the Merc engine will be fixed by replacing the block, then doing this swap should be very inexpensive. Since the oil pan may be different you may need a gasket. Then the carb gaskets, thermostat housing gaskets, lower unit gasket, exhaust miniflods and risers rubber stuff (hoses and clamps), belts, new filters etc, my guess 2 to 3 hundred when your done. That assuming everything from the Merc is useable. If the exhaust manifolds need replaced, risers, etc. bellows etc. then more.