1978 Merc. 1500 with blown powerhead

[ottsixx]

I just bought a 1978 Cajun boat from a fella who was reconditioning the boat and took it out for a spin and was running it balls to the wall and on the 5 th pass across the lake the powerhead blew,No. 3 plug has a lot of metal chips or shavings on the plug as you can turn the flywheel a lil ways in the clockwise and then it locks up and then you can reverse it and at some point it will also lock up again,I am curious what has gone wrong inthe power head and is it worth rebuiloding or just better off to buy another powerhead.....

 

[CRFan1]

Re: 1978 Merc. 1500 with blown powerhead

I just bought a 1978 Cajun boat from a fella who was reconditioning the boat and took it out for a spin and was running it balls to the wall and on the 5 th pass across the lake the powerhead blew,No. 3 plug has a lot of metal chips or shavings on the plug as you can turn the flywheel a lil ways in the clockwise and then it locks up and then you can reverse it and at some point it will also lock up again,I am curious what has gone wrong inthe power head and is it worth rebuiloding or just better off to buy another powerhead.....

Personally, It sounds like you you broke a ring and it is snagging on the port. Gonna have to come apart as this usually does damage to the cylinder as well, unfortunately....Get someone to take a look first though. Sorry man that sucks!

 

[Chris1956]

Re: 1978 Merc. 1500 with blown powerhead

Pull off the transfer cover on the starboard side of the motor and shine a light into the plug hole on #3. You will likely find a broken connecting rod. if the damage is confined to cylinder #3, and you can rebuild it yourself, it may be worth doing. It will cost $150 for a new overize piston set, and some gaskets. The cylinder will need to be bored out, and you will need to price out a new connecting rod, main and wristpin bearings.

However, I think there is a high probability that you damaged the crankcase when you broke the connecting rod, and the block may be junk. The only way to know for sure is to open the crankcase and look around.

BTW - The last Merc 1500 was made in 1977.