Coil pack 92 nautique, possible symptoms?

Hi Guys,

I'm troubleshooting a 92 nautique over here in blighty and suspect the coil pack.

cyls 6, 7 and 8 are sparking but it seems they are firing either to early or too late meaning that there is little or no combustion on those cylinders.

Initially I suspected it to be a fuel problem as the boat started playing up after cleaning the spark arrestor (was full of alternator belt shavings). The boat runs on propane (like many do in europe) and often the slightest change in airflow will affect the mixture.

Any how after fully checking the fuel system it is defo the ignition because of the following :

1. Sometimes runs fine, other times it missfires and then surges
2. On pulling leads 6,7 and 8 whilst running there is little chnage in RPM (but good spark from lead to ground).
3. Exhaust manifold on that side is cold, other side is warm so I suspect this means no explosion on those 3 cylinders.
4. Exhaust smells of fuel, particually when running poor.
5. Engine backfires through both the carb and exhaust everynow and then.

Now I've read before that the coil packs on these can be troublesome. Could these be playing up meaning they are not firing at the correct time?

Any ideas?

Turns out it's water in the bores. Pulled plugs 6 7 and 8 today and they are wet and rusty.

I'm guessing manifold/riser issues causing this.

Jay,
Could be head gasket also