stott71

Here's the email I sent to my mechanic...anyone have any ideas?

I’ll try to summarize what’s going on with the boat.

Initially, both engines ran quite strong after the rebuilds/reinstall in the last few weeks, although in retrospect the port side engine may not have idled quite as smoothly as the starboard (subtle difference). Last week at the beach, extended periods in no wake zones (10-30 min) seemed to cause the port engine to run poorly when getting back up on plane . Towards the beginning of the week, the port engine would sort itself out in a few minutes and run strong, but by the end of the week, the port engine was running poorly all the time and would not exceed 3400 rpm even at full throttle. It seemed at this point like it was running on 7 cylinders. I swapped ignition coils from one engine to the other and the poor performance continued on the port motor. I looked down in the carb at idle and didn’t see any excess fuel dumping down there, so I don’t really think it’s a fuel delivery problem.

On a possibly separate issue, the port motor would not restart (battery power?) when hot, only after cooling off. Advance Auto Parts tested the battery and said it needed a charge, and I remembered you said the battery wouldn’t hold a charge about a month ago, so I replaced the battery and now the port engine will re-fire with no problems even when hot.

What I’m thinking at this point is that plug wires or distributor cap could have an issue, even though they are new within the last 2 years, so I’ll swap them from one motor to the other to eliminate that as a possibility. If the port engine problems persist, I thought I’d check and see if any of my plugs are fouled. Beyond that, I’ll double check the ignition timing and then perhaps do a compression test.

One other piece of info, not sure if it’s relevant, is that both engines appear to get ignition power from the starboard side electrical system, because the port side battery cutoff only controls the port starter (you can turn off the port battery switch while the port engine is running and it will stay running). I didn’t know if having both engines electrical run off the starboard side could be causing voltage fluctuation and/or plug fouling.

stott71

Update to the last post: Checked all plugs and #1 cyl was black and covered in gas, all the rest of the plugs were fine. Compression test is consistent on #1 cyl and 2 other cylinders we tried. We're thinking it could be as simple as a bad plug or plug wire . I'll let you know what I find out.

Griff

Its probably running a little rich at idle. Fouls a plug or two and then does not completely recover. The problem will get worse when one plug fouls since there is even more fuel that won't burn off and then more plugs will foul.

stott71

Port engine appeared to run better after replacing the #1 plug and plug wire and coil, but still would not rev past 3400. Thought it could be a fuel check valve problem so I checked that and pulled out a chunk of plastic that had to be blocking some fuel. Engine ran better, as high as 4200 rpm, but still had an intermittent miss around 3100. Later had just gotten up on plane for about 1/2 mi (engine was definitely missing) when the port engine went dead and stayed that way, no spark, wouldn't even pretend to start. Plenty of fuel getting there, but found a very loose wire connnection with the wires leading to the ignition module and distributor. I'm thinking this is what caused the intermittent missing, fluctuating tach and the inability to rev very high. I'm also thinking this loose connection and fluctuation caused the ignition module to go bad...so that's what I have to try and fix next.