mirage 29 petrol head gasket blown twice on one engine.

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Joined: Wed Sep 14, 2011 8:57 pm
Location: fairline mirage 29

mirage 29 petrol head gasket blown twice on one engine.

Post by benegfr » Wed Sep 14, 2011 9:17 pm

Can anyone help? Second blown head basket on one of a pair of 3.0L PETROL penta engines. Someone told me it could be an exhaust flap issue allowing water back into the engine. Doesn't seem likely but has anyone heard of anything like this happening as the engines are low with respect to the waterline. She does drag her stern rather even with full water tank in the bow.

It will tow a wake-board! Getting a bit fed up of 3.0l 'rebuilt' petrol Volvo pentas though. Sark is great and a mirage a nice place to sleep there.

Spi D
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Post by Spi D » Thu Sep 15, 2011 5:37 pm

Are you running at normal temperatures at all times?

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Location: Fairline Mirage

Post by ms » Tue Sep 20, 2011 2:51 pm

The difficulty with problems such as yours is that everyone has an idea ... all are valid (to a greater or lesser degree) and you have to try to make sense of them all.

My limited experience suggests that with significant actual water ingress into the cylinder you are more likely to get a bent connecting road than a blown gasket ... so I remain sceptical about the water coming back up the exhaust system. Easy enough to check though .. get the boat out of the water and fit a new exhaust bellows.
Do you know when this was last done ?

Now .. CYL heads do go of their own accord on old engines from time to time so reason for incident 2 is more worrysome.
Was CYL head skimmed before it was re-fitted.
Was CYL head tightened down with a torque wrench, and was it re-tightened after some hours of running.
Is it possible to determine if it was the same actual cylinder that caused the problem.

... Two of those big engines ..... she must me very low in the water at the stern. Do you have ballast in the bow ? ...

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