Bear with me while I give you all the information I have...I apologize in advance for the length.
The boat is a 1992 Wellcraft Eclipse XL. Engine is Volvo Penta 431A with dual props. I "inherited" this boat with a bad engine (Spun rod bearing and holes in 2 pistons) from my father-in-law. The boat had always run great but the first trip out last year she gave up the ghost. It was supposedly winterized/de-winterized at a nearby marina.
Soon after getting the boat I rebuilt the engine with the help of my dad. Everything went reasonably well with the rebuild. We installed the engine and to our surprise it fired up right away without much timing adjustment. One thing that perplexed us a bit was that the spec for timing is 8* btdc at 800 rpm and something like 18* at 2500 rpm (this is printed on the engine cover). We set it at 800 but at 2500 it was in the mid 20's. It sounded fine so we figured we'd take it out to see how it ran. Well, it ran good, really good.
Fast forward a few weeks and probably 8 to 10 hours of running. Had it out skiing and it suddenly dropped a cylinder. No. 1 spark plug was basically melted. This was near the end of summer, so I didn't mess with it again until this year.
This spring I stuck a new plug in there and it did the same thing within maybe 15 minutes. At this point I decided to let someone look at it. My mechanic said the valves were out of adjustment as was the timing and it needed a dist. cap. He set the timing and valves and I put a new dist. cap on it. He also noted that the carb was dumping a LOT of gas in the engine, so he turned it down as far as he could. I go back on the water and it runs awesome, I mean better than ever, for about 15 minutes and then loses a cylinder again. This time it's number 2. By the time I limp back to the boat launch it's running really bad. No. 1, 2 and 4 plugs are damaged.
At this point my mechanic does a compression check and suspects valve damage to three cylinders, which was correct. I had head jobs done on both heads. Took it back out this weekend and it ran really bad right off the bat. It will barely plane out. No.1 plug ground had slight damage. Note that all these damaged plugs I'm mentioning look like pre-ignition from all the photos that are in repair manuals. One actually had gap bridging (probably from a piece of valve).
I start thinking that he may have starved the engine for gas when he adjusted the carb. I added some fuel to the mix just to see what it would do. It still ran terribly, but it didn't kill any plugs. This is probably because I only ventured about 200 yards from the dock this time.
I am at a complete loss at this point. All cylinders are firing now, but it can't get out of its own way. I'm going to take it back to my mechanic since I feel he should have caught whatever the problem is by now. All the while, I've spent some good money letting him basically get me where I was last year.
I feel that it's GOT to be something in the ignition or in the carb. Hopefully someone here can give me some help. I'm scared I'm going to further damage the engine.
Thanks
Brad
The boat is a 1992 Wellcraft Eclipse XL. Engine is Volvo Penta 431A with dual props. I "inherited" this boat with a bad engine (Spun rod bearing and holes in 2 pistons) from my father-in-law. The boat had always run great but the first trip out last year she gave up the ghost. It was supposedly winterized/de-winterized at a nearby marina.
Soon after getting the boat I rebuilt the engine with the help of my dad. Everything went reasonably well with the rebuild. We installed the engine and to our surprise it fired up right away without much timing adjustment. One thing that perplexed us a bit was that the spec for timing is 8* btdc at 800 rpm and something like 18* at 2500 rpm (this is printed on the engine cover). We set it at 800 but at 2500 it was in the mid 20's. It sounded fine so we figured we'd take it out to see how it ran. Well, it ran good, really good.
Fast forward a few weeks and probably 8 to 10 hours of running. Had it out skiing and it suddenly dropped a cylinder. No. 1 spark plug was basically melted. This was near the end of summer, so I didn't mess with it again until this year.
This spring I stuck a new plug in there and it did the same thing within maybe 15 minutes. At this point I decided to let someone look at it. My mechanic said the valves were out of adjustment as was the timing and it needed a dist. cap. He set the timing and valves and I put a new dist. cap on it. He also noted that the carb was dumping a LOT of gas in the engine, so he turned it down as far as he could. I go back on the water and it runs awesome, I mean better than ever, for about 15 minutes and then loses a cylinder again. This time it's number 2. By the time I limp back to the boat launch it's running really bad. No. 1, 2 and 4 plugs are damaged.
At this point my mechanic does a compression check and suspects valve damage to three cylinders, which was correct. I had head jobs done on both heads. Took it back out this weekend and it ran really bad right off the bat. It will barely plane out. No.1 plug ground had slight damage. Note that all these damaged plugs I'm mentioning look like pre-ignition from all the photos that are in repair manuals. One actually had gap bridging (probably from a piece of valve).
I start thinking that he may have starved the engine for gas when he adjusted the carb. I added some fuel to the mix just to see what it would do. It still ran terribly, but it didn't kill any plugs. This is probably because I only ventured about 200 yards from the dock this time.
I am at a complete loss at this point. All cylinders are firing now, but it can't get out of its own way. I'm going to take it back to my mechanic since I feel he should have caught whatever the problem is by now. All the while, I've spent some good money letting him basically get me where I was last year.
I feel that it's GOT to be something in the ignition or in the carb. Hopefully someone here can give me some help. I'm scared I'm going to further damage the engine.
Thanks
Brad
