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Hello,

I'm rather hoping somebody can offer some advice or words or wisdom here...

About a year ago, I bought a Shetland 570 with an inboard OMC sterndrive setup. On the first trip out, the engine started billowing black smoke and everything stopped - it turned out it had overheated and seized.

I had the engine rebuilt and, this week, finally finished rewiring it all and decided to test the electrics. I was fairly happy to find the battery still had enough charge to lower the drive leg, but not quite as happy to discover oil pouring out of the water intake just above the prop shaft...

This is the first time I've lowered the leg since the stupid thing blew up, so I assume this is symptomatic of the reason why. I also assume that a seal has gone on the drive shaft and the oil had pooled around the impellor, waiting for the day I lowered the leg and it could all drain out...

The sterdrive is a Stringer 400/800 model number 980701, serial number 120B 4290 - it is, indeed, the same sterndrive as Noah fitted to the Ark (I'm reliably informed). On the off-chance that somebody out there knows how these things work, I'd be very interested to know what they think has happened and, to the nearest power of ten, how much it's likely to cost to repair.

Any thoughts, comments or sage stroking of beards will be much appreciated,

Many thanks,

Paul
 
Don't know much about the stringer but did have an OMC cobra for a number of years.

Assuming the oil is coming out of the water intake and not from around the propshaft. It may be possible that what you are seeing is in fact engine oil rather than leg oil. If the engine failed that badly, the oil could have ended up in the exhaust and cooling systems to find its way to the leg.

Have you checked the level of oil in the drive?

Someone who knows these drives better than me may say differently but I am struggling to see how leg oil could end up coming out of the water intake unless the leg itself has corroded through!

If the oil is coming from around the propshaft, it may just be the propshaft oil seal that needs replacing.
 
It's a good thought (and I rather hoped that when I saw the oil) but I'm pretty sure it's gear oil from the leg...

When the engine siezed, apart from the smoke and clattering noise, it was fairly undramatic - certainly no oil seemed to escape visibly. When I then stripped down the engine prior to craning it out, there was no oil in the exhaust, which is the only route into the drive unit from the engine. Also, the oil that came out of the water intake was nice, clean and green - the oil in the engine sump was black and well used at the time of the blow-up...

The way an OMC drive leg is arranged internally is essentially with a drive-shaft passing all the way through it from top (where the engine drives it via a 90 degree pair of gear) to the bottom (where an electromagnetically switched gearbox drives the prop either forward or in reverse) with the waterpump impellor attached about mid-way down. From the diagrams in the manual I've got, it seems that the top of the drive leg is filled with oil, as is the bottom, whilst the impellor is in a chamber with seals above and below - the driveshaft itself acts as an oil pump, having an archimedes screw along part of its lower length.

I'm fairly certain one of the seals has failed rather than any corrosion has occurred internally...

All the best,

Paul
 
Ok that makes sense. I think you will have trouble finding anyone with the knowledge of old OMC drives to do the work to a decent standard. If it were me I would looking at doing it myself with the help of a maunal and use of those US based forums where you will find loads more OMC savvy people than you will this side of the pond.

When I was an OMC owner there was a company called L&J marine based in Hampshire who were reputed to be 'THE' OMC specialist in the UK. Never used them myself but may be a source of parts and advice. Google them for contact details.
 
I'll look them up, thanks for that.

I'm tempted to do it myself on the grounds that I can't really make it any worse than it already is...I was just put off by the full page of WARNINGS and CAUTIONS in my manual regarding trying to get at the impellor...

Still....how hard can it be?

Thanks,

Paul
 
Hello Paul,
Having recently rebuilt one these drives it sounds like the double lip seal at the bottom of the upper gearbox has gone allowing oil to leak through into the water pump housing and out through the water intake at the bottom of the leg. The upper and lower gearboxes are separate sealed units. The leg needs to be removed from the boat to do this. Disconnect the gear cable from the shift mechanism inside the boat at the back of the engine, tilt leg up and remove the gear cable retaining clip where it passes through the back of the intermediate housing. Remove the hinge bearing rubbers and caps, with the leg in the straight ahead position undo the hinge cap bolts and pull the leg away from the boat while taking care to pull the gear cable through at the same time. The tilt quadrant may have to be removed to achieve this. Remove the top coverplate from the leg taking care as there are shims underneath it, once removed the upper gearbox will come away from the rest of the leg. The waterpump housing is then removed from the upper gearbox to get at the seals. It is worth considering replacing the rest of the seals in the gearbox as they will now be quite old and starting to become hard. It is quite a straight forward job but be prepared for seized and sheared bolts! Parts are readily available from the USA at very reasonable prices and quick delivery times. Try googling "omc 800 Stringer" and it should come up with several suppliers.
Hope this helps.
 
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It sounds like the bottom oil seal has failed on the vertical driveshaft in the upper gear box allowing oil to escape through the waterpump housing. The lower and upper gearbox are seperate sealed units and the vertical shaft is made up of three parts. The leg will have to be removed from the boat to take off the upper gear box for a strip down. The crown wheel has to be removed from the vertical shaft to remove the shaft from the bearing box to get at the seal. I have recently had the pleasure of stripping and rebuilding one of these drives! PM me if you need more info.
Regards.
 
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