OMC to Mercruiser Conversion, Should I do it?

[reavesga]

I am currently running a 1973 OMC 140 HP OMC Stringer Sterndrive. It has run fine for two seaons now after about a $1000 investment in the ball gears, bearings, and a water pump. Last Friday it "slipped" out of gear. Turned out it was the shift switch. A frantic google search turned up omc-switch.com where you can get the switch rebuilt. Expensive though. Also found one on e-bay which is installed right now and will hopefully get me through the weekend. Anyway this got me thinking about parts availability and cost. I have a complete 1974 Mercruiser MC-1 that is in good shape. A lot of folks have said I need to swap the MC-1 in as parts are still available. What I want to know is; is the swap is worth the trouble just to get a Mercruiser drive?

I have the problem of the large OMC hole in the transom solved. Boat is Aluminum transom plate can be bolted in and out so building up a new transom is not a big deal. It looks like the hardest thing on the job is going to be just physically moving the engines around as I don't have an over head lift that can reach up into the boat.

Would love to hear from folks that have contemplated the same issue. If you have done this swap, what problems / challenges did you run into and were you happy with the result?

 

[HT32BSX115]

Re: OMC to Mercruiser Conversion, Should I do it?

Howdy,


I think you should do the swap if you really like and cannot live without the boat.

Otherwise, it might be just as good to sell the boat and get another one with the engine/drive combo you like.

What I want to know is; is the swap is worth the trouble just to get a Mercruiser drive?

You have the hard part figured out. (big hole/small hole)

I would even suggest looking for a much newer engine and drive.

Or, find a Merc gimbal and associated parts and get an SEI drive. This way you install a new drive with a 3 year warranty.



There's a lot of possibilities most all will take a fair amount of money and time to "get to the water".

I did it removing a 460 King Cobra,replacing with a 454 Bravo III.

I didn't have to do anything with the cutout and I had everything for the swap.


I also was able to sell all the OMC "Stuff" for about $3400 so far (I still have a few parts and 2 props left!! & I paid $5k for the Merc)


If you like projects...then it'll be fun.......If you like boating it might be better to sell yours and buy something else!


Good luck,


Rick

 

[reavesga]

Re: OMC to Mercruiser Conversion, Should I do it?

Are the SEI drives a good alternative? Basically I have a complete donor boat, drive, controls, everything. The owner spun a bearing in the engine last season and has lost interest in fixing it. He was going to just haul it to the junk yard so I offered a couple hundred for it and now I own it. Drive was reported as running fine at time of removal.

How about the tool that I have read about for drilling the transom? Do you know where I can get one? Is it required? I had just planned on matching engine crank shaft position. Kind of backing into the problem by locating the inner gimbal to components to match the engine heigth in the boat then locating the outer gimbal.

The boat is a 1974 Crestliner Cuddy Cabin. We really like the style of the boat and you don't see to many of them on the water. At this point I have a grand total of $200 invested in the donor boat.

 

[HT32BSX115]

Re: OMC to Mercruiser Conversion, Should I do it?

He was going to just haul it to the junk yard so I offered a couple hundred for it and now I own it. Drive was reported as running fine at time of removal.

Well,


that's somewhat different.

You may not even have much to "part-out"!

Are the SEI drives a good alternative?

I have not done one but most everyone here that installed them have been happy with them......

Going with the most modern parts ensures that you'll have an easy time finding replacement "stuff" when needed.

How about the tool that I have read about for drilling the transom?

I think Don and and a few others here have the template that you can download

The best way to do it is to get a Mercruiser installation manual and do the measurements (X dimension etc) the way they suggest.

In general, once you locate and cut the hole, install the gimbal mount and inner transom plate, you make/locate the front engine mounts. The rear engine mounts are already on the inner transom plate.

Over in the
Boat Restoration, Building, and Hull Repair

You'll find a whole bunch of people that have done what you want to do!



Regards,


Rick

 

[reavesga]

Re: OMC to Mercruiser Conversion, Should I do it?

Decision made for me. Something let failed this weekend under power. The lower unit is all jammed up and something is wrong in the transfer case. So out it comes.

 

[wire2]

Re: OMC to Mercruiser Conversion, Should I do it?

My '84 OMC V8 stringer drive was running fine 2 years ago, I still decided to change to a late model alpha just for ease of mind.
http://forums.iboats.com/showthread.php?t=225270
Don't worry about not having a hoist, a 4 banger is manageable by hand with 2 people. It's easier if you chain a tube across the top of it for a handle.

 

[reavesga]

Re: OMC to Mercruiser Conversion, Should I do it?

Conversion is in progress. Built a new transom and coated in epoxy. I have discovered that the back of the boat is not even close to flat. So the new transom that is does not fit very well. The cardboard template fits nice, but obviously it would bend around the metal transom.

The metal and wood match up pretty good in the area where the stern drive will mount so that is nice and flat like it is supposed to be. But at the top, there is about a 0.5" gap between the wood and the metal. I have tried to draw it together, but no luck. A straight edge across the back of the boat shows that it is bowed inward.

So here is the question, can I pour expanding foam into the gap, which I know does not go all the way down and let it cure to get a "custome" fit, or should I just cut the top 8" off the ply wood, which has no fasteners in it anwyay. Or just leave it.

I am somewhat worried about foam due to water, however, all of this is well above the water line so maybe it is not an issue.

 

[cimy3]

Re: OMC to Mercruiser Conversion, Should I do it?

You could always pour Seacast in it and then no worries about water rotting it away.
Check it out....

http://www.transomrepair.com/catalog

 

[reavesga]

Re: OMC to Mercruiser Conversion, Should I do it?

Does it have any expanding properties to fill voids? Also when I say pour I really mean pump through a tube. This is an I/O situation so the top of the transom is not readly accesible.

 

[wire2]

Re: OMC to Mercruiser Conversion, Should I do it?

Does it have any expanding properties to fill voids? Also when I say pour I really mean pump through a tube. This is an I/O situation so the top of the transom is not readly accesible.

Seacast does not expand to speak of. If you need to push the aluminum plate away from the wood, try to drive some tapered hardwood dowels down into the void, then pour Seacast around/past them.

The Seacast will consist of liquid resin, paste hardener and recycled fiberglass strands. In your case, if you need to pump/pour it, don't add the fiberglass, or add very little of it. Call/email the folks at Seacast, they're very knowledgeable.