2GM Yanmar Oil in Exhaust

[Blue Crab]

Please cut to the chase, cap. I'm outta popcorn.

[miabellabrian]

Not sure what my hull speed is I guess around 7 knotts ?? 25 foot contessa, anyway ATM that is the least of my concerns, I was getting good speed 8 knots no problem at all. I know the boat needs a hull clean but isnt too bad, as it has the soft antifaul that comes off.


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[miabellabrian]

Lol

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[Cheechako]

If you've got a lot of blow by, then likely your engine needs a lot of work.

[GrahamHO]

Originally Posted by Cheechako

If you've got a lot of blow by, then likely your engine needs a lot of work.

If his engine starts OK and he gets any issues with the prop sorted out he could probably live with a little oil consumption even if it kills a few fish. That is if he is only sailing around Lake Macquarie and not going out into the ocean. If he has an anchor and sails he shouldn't get into any trouble there.

If or when it does its final dance of death a 15 HP four stroke outboard on a bracket would be a good cheaper option than a rebuild of a 30 year old motor. A long shaft model might be worth considering. Then his yacht should sail better with a total of maybe 150 kg removed including the prop and shaft drag. Four strokes of course are better for a displacement yacht and use less fuel and have less fumes.

Meanwhile as Sailorchic34 suggests it's probably a good idea to simply do a head gasket change (using ample but not too much gasket goo). I seem to remember the head gasket is around $100

Then live with it and go sailing.

[Cheechako]

He eliminated the idea of "bubbles in the coolant" on a later post. Certainly nothing wrong with cleaning up the head and a new gasket though. I'd definitely get the head tested and or rebuilt if going to that trouble. But I'm just not seeing a head gasket as a likely oil in exhaust problem. Possible, but....

[sailorchic34]

Originally Posted by GrahamHO

Good info. I'm not wishing to contradict you but the head nuts or bolts should be loosened in the reverse order from tightening. That is loosen the outside nuts first and the loosen center nuts last.

You are correct. Thank you for that correction. Darn senior moments.

[GrahamHO]

Originally Posted by sailorchic34

You are correct. Thank you for that correction. Darn senior moments.

Bet I'm older than you! I don't think the loosening order is a important as the tightening order.

[sailorchic34]

Originally Posted by Cheechako

If you've got a lot of blow by, then likely your engine needs a lot of work.

If his head gasket is blown at the pushrod galleys then he can get blowby leaking at the head gasket. Plus as oil is returned from the rockers via the same galleys that oil could be pulled into the cylinder on the intake stroke. So it's possible to have both with a blown head gasket.

From personal experience, if rings were bad/broken on one cylinder to cause blowby like that, the engine would be very hard starting. Requiring many chants and questioning it's parentage. Been there done that.

Though if only the 2nd and oil rings are toast, then it might still start easy but smoke and have blowby. Though when I had one bad piston (all three rings and lands broken) there was no smoke when running and very little oil. It drank and burned tons of oil though.

That's why with easy starting but blue smoke, I lean towards a head gasket. Grey smoke could be sticking injectors, and black smoke would be over proped or fouled prop.

The sailorchic method for checking if the rings are good is once the head is removed, pour a cup of oil in each cylinder and let it sit for 12 hours. If the oil has not dropped much or at all, the rings are good. If one hole has lost oil, then it has bad rings and your rebuilding the engine.

[Cadence]

Originally Posted by GrahamHO

Bet I'm older than you! I don't think the loosening order is a important as the tightening order.

I may be older than you? Loosening in the right order may be keeping it from warping? It is hard to think of a slab if metal warping but it can.

[Ocean Diamond 2]

Originally Posted by miabellabrian

Lol

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Hey Brian,

I had a Dehler that went through 2 2gm20 Yanmars and 2 3gm30's so I have some experience and I'm local.

You should try Minards Diesel service, the local Yanmar agent. They helped me a lot.

When you get it fixed can I come for a ride as I've never been on a Contesa 25 and would love to experience 9 knots

Good luck mate,
Derek

[GrahamHO]

Originally Posted by Cadence

I may be older than you? Loosening in the right order may be keeping it from warping? It is hard to think of a slab if metal warping but it can.

Yes as I said a couple of posts back, you should loosen in the correct order but I think tightening in the correct order is even MORE important as it allows the gasket to settle in "flatly".
I didn't say it is not important to loosen in the correct order and I always do that.
I just knew somebody make that comment.( I did make a typo writing "a" instead of "as" but my meaning should have been clear)

[GrahamHO]

Originally Posted by Ocean Diamond 2

Hey Brian,

I had a Dehler that went through 2 2gm20 Yanmars and 2 3gm30's so I have some experience and I'm local.

You should try Minards Diesel service, the local Yanmar agent. They helped me a lot.

When you get it fixed can I come for a ride as I've never been on a Contesa 25 and would love to experience 9 knots

Good luck mate,
Derek

You'll need to wear good wet weather gear as the bow wave from a Contesa 25 comes back into the cockpit

[Cheechako]

Originally Posted by sailorchic34

If his head gasket is blown at the pushrod galleys then he can get blowby leaking at the head gasket. Plus as oil is returned from the rockers via the same galleys that oil could be pulled into the cylinder on the intake stroke. So it's possible to have both with a blown head gasket.

From personal experience, if rings were bad/broken on one cylinder to cause blowby like that, the engine would be very hard starting. Requiring many chants and questioning it's parentage. Been there done that.

Though if only the 2nd and oil rings are toast, then it might still start easy but smoke and have blowby. Though when I had one bad piston (all three rings and lands broken) there was no smoke when running and very little oil. It drank and burned tons of oil though.

That's why with easy starting but blue smoke, I lean towards a head gasket. Grey smoke could be sticking injectors, and black smoke would be over proped or fouled prop.

The sailorchic method for checking if the rings are good is once the head is removed, pour a cup of oil in each cylinder and let it sit for 12 hours. If the oil has not dropped much or at all, the rings are good. If one hole has lost oil, then it has bad rings and your rebuilding the engine.

Yeah I hear you on the 2 cyl. If one cyl is very bad it should be pretty rough or hard starting. Amazing how on a 4 cyl you cant tell there's a problem at all sometimes with one bad cylinder.

[Wotname]

Just some pure specualtion follows
We now know the engine is 30+ years old.
Assume engine has been used lightly for most of the time, especially as a Contessa 25 probably needs only say 6 hp to reach hull speed in calm waters like Lake Macquarie.
Plenty of carbon build up over the years masking the wearing of rings / bore.
Recently run a WOT for an hour or so has broken up / burnt the carbon thus now seeing the true effect of worn rings.
Perhaps a blown gasket to boot.

If this is what happened then one possible cheap solution is take head off to check head gasket, do the sailorchic endorsed quick and dirty ring check and providing the oil isn't gushing though the rings, reassembled and use a slightly heavier grade of oil , say SAE 40.

Keep running lightly, keep the oil up, maybe toss in a can of "magic instant rebuild/smoke stopper", and allow more carbon to build up to help seal the worn bore.

Cold starting might b e an issue but it doesn't get that cold at Lake Macquarie and even that can be overcome by external heating if necessary. One advantage of the 2GM over the 2GM20 is that the 2GM has a slightly heavier flywheel which should aid cold starting when used in conjunction the decompression levers.