DT115 1986 Motor died

"We were water skiing, been ru

"We were water skiing, been running probably 20 minutes when the motor hesitated then died. We were low on fuel so thought that might be the problem. Put some in the tank and carried on. Went about a kilometre then died again just as if the ignition had been cut. It fired up straight away and repeated this about 4 times back to base.
Took it out next morning and once warm the motor played up again in the same fashion. Removed the hood and felt the head and cylinders. All seemed similar temperature. Water telltale was squirting strongly, hot on our hands. Motor was reluctant to idle when retrailering the boat. No warning lights nor buzzer activated. Motor ran quietly as opposed to previous seizures when there was a ‘ticking’ sound.
Compression check shows 3 cylinders 115psi but no.2 only 70psi. We haven’t yet removed the head.
The motor has done 746 hours, we’ve had it since new, only used it in fresh water 12 - 18 degrees C (54-64F) but has seized 3 times over the last 150 hours, we think the 1st time caused by a worn crankshaft lower seal so leaning the fuel mixture, the 2nd by the shaft rotating inside the pump impellor, the 3rd we know not why. “Cold water seizure” was suggested but I ask how do motors used in Alaskan waters get on? Had the oil analysed and it was perfect. Have done about 40 hrs since then and used 95 and 98 octane petrol exclusively for that time (previously used 91).
The affected cylinders were bored and oversize pistons fitted each time. From memory this is the 3rd time that no. 2 has played up.

Any ideas re what the problem might be and possible causes are most welcome. These failures are expensive!"

"Alan, That ticking noise soun

"Alan, That ticking noise sounds like a scored piston(s). I would guess you weren't getting fuel to one or more cylinders and the lubrication it needed thus causing the scoring. The reason for the lack of fuel/oil getting to one or more cylinders my rest with a compromise in your fuel delivery system. A possible culprit may be a pin hole in a fuel line or bad connection that sucks in air while running, particularly at higher speeds. Hope this helps."

Thanks Richard. We have since

Thanks Richard. We have since lifted the head and there is scoring all round the bore down the cylinder (rather than in line with the gudgeon pin or around the top of the cylinder) which suggests lack of lubrication for one reason or another.

We're not sure now whether to fix it or give up boating.

"Alan, if you choose to stay w

"Alan, if you choose to stay with boating and fix the motor replace all the fuel lines and refit all the connections to eliminate any air leaks. If you pressurize the old fuel lines with compressed air I'll bet you'll find a leak, or two.
I can feel your frustration with boating when things like this happen. You have to remember one thing and that's what the acronym B.O.A.T. stands for: Bring Out Another Thousand!
I wish you the best."