Mercruiser 260 V8

Question
Hi. I am having trouble with a marine engine.

Its a Mercruiser 5.7 V8 260hp engine.

Its a bit of a long one, but I started with no compression on 2 cylinders. Had
the heads reconditioned, new plugs, gaskets, the whole shooting match. Now
good compression of 90-110 at idle.

Unfortunately due to my inexperience I didn't seal the headbolts which I now
understand are pourus. And never drained the 2 drain taps on the side of the
block after running it with water going thru.

In the process of heads reconned and starting, she became tough to start and
the starter blew a few teeth of the flywheel.

Back to the shop who replaced the flywheel but are now continuing to have
trouble starting the engine.
Initially the engine starts OK'ish, but then starts to slutter and cuts out (fuel
has been in the tank 10-12 months)

The boat has a small amount of milky oil, either thru the headbolts,
condensation as sat in my drive with heads off while being reconditioned
(with a tarp on)  or its another problem.

Q1. would you agree that the headbolts may have let the water in?
Apparently not that milky.
Q2. any ideas on the not starting
Q3. Could the old fuel (10-12months) be causing problems.

Any help would be much appreciated

funds now gone!!!!!! got a lovely drive blocker.......

Answer
Hi Steve...thank you for selecting the undersigned to reply to your question.

Depending upon how full the fuel tank was when the boat was last used, condensation may have built up and contaminated the gasoline. This problem can be effectively resolved by introducing one of a number of chemicals, and recommend you consult a reliable marine mechanic. Alternatively, the octane level may have become depleted, and again, there is an octane addative available at most automotive outlets, so follow the container's instructions.

When reinstalling the head bolts, its wise to insert silicone in the holes, then tighten the bolts according to the manufacturer's recommended degree of torque. Also, its possible the head gasket may be damaged or is defective, so check that out for sure.

If the crankcase oil is milky, drain and flush before introducing new oil. But, what concerns me is the failure of the starter and damage to the flywheel, which I suspect might have occurred as a result of the pistsons seizing, maybe. Something prevented the flywheel from turning properly and that problem needs to be explored and resolved.

I'm not a mechanic, so I recommend you consult and be guided by reliable professionals in the field. In the long run, it may save you a lot of money.

Safe Boating
Ron