Used 1978 OMC outdrive question

I have a 1979 OMC hooked to a GM 260 hp in a 20 ft Formula/Tbird. It's been an adventure the last 2 seasons but I've had some fun times in this girl. I really don't have a problem with being an OMC owner. That being said I'm trying to prepare for keeping it going the next few years. I changed the water pump and manifolds and she's staying cool now. Bad thing is the upper is getting water in it. The short term solution has been to keep good gear oil in it. I've changed it 3 times this season. I'm going to try to reseal it this winter.

I found a 1978 used outdrive from a V8 boat and I think (havn't seen it yet) that it's the same as mine, or dang close.

Here's the question, this dive was rebuilt by the people at sterndrive.com nine years ago and was never installed on a boat. The owner says is was a complete rebuild. He has the reciepts. It's a good deal and I'm thinking of buying it to help me get more years out of my boat. I could have a drive on the boat and one for a spare.

What are some of the risks I should be aware of with this plan? Could the seals have gone bad over the last 9 years, just sitting?

Re: Used 1978 OMC outdrive question

floattest said:

Could the seals have gone bad over the last 9 years, just sitting?

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That hasn't been my experience. The seals are lubed at assembly. Gear oil doesn't evaporate measurably.

My primary concern would be that the 78 drive (or your drive) was at one time converted from hydromechanical shift to full mechanical shift. That was a popular update that would make the swap a real headache.

compare the 2 lower units for the absence or presence of a rectangular zinc anode next to the 6 idle relief holes. If they match, probably a good investment.
Fun is all about a good stash of spares with stringers.

I'd also turn the steering worm gear on each drive to see if the two drives have the same steering direction parts in them (minor detail, but you want to know before you pull out of your slip and crash after swapping drives)

Re: Used 1978 OMC outdrive question

This turned out to be an electric shift so it wasn't of any use to me.

It's still for sale in Snohomish Washington.

It was rebuilt by a company in Everett and never installed.

look for it on craigslist in wa. seattle area.

Hope it helps an OMC owner somewhere.

Re: Used 1978 OMC outdrive question

floattest said:

This turned out to be an electric shift so it wasn't of any use to me.

It's still for sale in Snohomish Washington.

It was rebuilt by a company in Everett and never installed.

look for it on craigslist in wa. seattle area.

Hope it helps an OMC owner somewhere.

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It wouldn't have been a '78 then. '77 was the last of the electric shifts.

Re: Used 1978 OMC outdrive question

Leaking uppers are more often due to frost damaged walls than failed seals, (in my experience).

Did you try a vacuum (or low pressure) test thru the dipstick opening? 2-3 psi in it with soapy water sprayed at the shafts may tell a tale.

If you're going to open it anyway, look closely at the thin section adjacent to the water passage for a hairline crack (frost). If none, replace the seals. Generic seals are available from any bearing supply for half the cost of OEM, (maybe $30 for all 4). Remember to face the first one IN, the last one OUT.

I just had 1 more thought, you may have corrosion in the seal area of the housing, allowing water to pass around the seal.

Re: Used 1978 OMC outdrive question

Wow! A stringer upper box with water in it! Imagine that! They all do, they always will, due to the crappy sealing of the steering shaft, among other reasons. If I never see another OMC product, it will be too soon. 'nutcase

Re: Used 1978 OMC outdrive question

wire2 said:

.....Leaking uppers are more often due to frost damaged walls ......

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What exactly means this?

My upper is near 30 y/o, sits out in the winter (gets into the low 20's, enough to break blocks and manis) and never gets water in it.

Re: Used 1978 OMC outdrive question

WizeOne said:

It wouldn't have been a '78 then. '77 was the last of the electric shifts.

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HMMM....

I have a 200hp OMC/chevy 305 motor. Thing is the boat is a 1978 and theres no 200hp motor for '78.... there was in '79.

My OMC 800 drive is also electric shift.

Not sure what to make of all that but it is what it is.

I'm guessing they mixed and matched on certain models that were built early/late in the year.

Re: Used 1978 OMC outdrive question

do NOT use generic seals,why? because the seal is on a steel base and the girdle springs are normal steel, the proper seals are made out of stainless steel. a generic seal will not last.