98 gt40 low compression…HELP..no start

[mtrader]

Hi been struggling to figure out my problem….2 weeks ago I take my 1998 gt40 out for a spin..after a few minutes on the water it dies on me. I was going about 30 mph or so and I heard no noise and the motor didn’t overheat. Oil pressure was about 40. I thought I may have run out gas so I added some fuel cranked it but nothing. Then The starter seemed to not want to turn after a few attempts. Like if it was stuck. I got back to the dock and the starter was really hot since I tried a few times to start it. After a while I left it alone and the starter would crank but it wouldn’t start. Fast forward a few days….motor cranks over but still no start even tried starter fluid in intake… Fuel pump is working, spark is weak, but compression on 2 cylinders reads zero and a few others were 60 to 90 range. No water in the oil. Plugs are clean as well. About 700 hours on the motor. I’ve owned it for 12 years always fresh water for me. Bought it with about 350 hours. Changed plugs, cables, HP fuel pump, filters, alternator, all within the last year or so. Any idea if this could be just changing out the heads? Or is there some other damage? I’ve considered getting a new coil to see if that helps w the spark but maybe it’s a good thing that it’s not starting bc maybe I’ll just do more damage n that low compression can’t be good. Thanks for the help.

[malibud]

0 compression that seems odd I'd recheck that

[Rusty Barras]

jumped timing chain? or broken chain? I agree zero compression seems odd.

[gary s]

Have a leak down test performed it will tell you where the problem actually is

[mtrader]

I checked the compression again today port side 95, 0, 45, 45....starboard side 85, 0, 100, 50 we removed the manifold and the guy helping me out said look at the one where it reads 0 looks like the piston made a grayish mark there. He also said the rubber hose connections to the exhaust tubes looked really bad on the inside. Like if they had expanded or something and maybe blocked the water flow and caused the boat to overheat. But as I said earlier that last day it ran it didn’t overheat on me.. I stopped there and didn’t remove any more parts. In the next few days I will remove the valve covers and keep checking.

I was told that since the motor isn’t running I can’t really do a leak down test. Is that correct. Any other thoughts?

[gary s]

No he is not correct. A leak down test pressurizes the cylinder with air and you measure how much leaks out. Now in your case if you hear air escaping from the exhaust or intake you know it's a cylinder head problem/head gasket, air leaking elsewhere could be an internal block or piston problem.

[mtrader]

Ok so still working on this… I have someone coming out this week to dig a lil deeper and get those look tests done. Just last week I had the exhaust manifolds removed by a guy that came to look at it and we noticed a grayish color on one of the ports. the guy said he thought that could be a damaged piston. I’ll post a pic now. Also about a year ago I had a damaged spark plug and we had a bad misfire. Replaced the plug and the boat ran fine right after. I’ll post a pic now of that plug too. Wondering if that was a sign something was going bad?

[mtrader]

here is the pic it is the 3rd one from the right

[mtrader]

Here is the plug from about a year ago. Wondering if this was telling me that the piston or something else was going bad… thoughts ?

[mtrader]

So dug in deeper and looks like 2 bad pistons, and the heads are cracked too. so motor needs a complete rebuild …. Spoke with some mechanics and may jump on this in the next few days finally. A machine shop can rebuild it but I guess I need a bunch of new parts as well… manifolds, injectors, risers , exhaust tubes were shot also…muffler too I think because boat has been taking in more water than normal for a while so …. Keep y’all posted. Any suggestions or opinions add them in here ..thx

[JDC02SANTE]

Hey mtrader, not sure what it will end up costing you to rebuild, but I recently saw a '95 GT40 w/ a Transmission for sale on the GT40 Marine Engines group on "the facebook". I'll see it is still on there if you think it is worth a peek?