So here it is. I have a 2005 Trophy Pro 2359 with a Mercruiser 5.0L carburated. When I bought the boat this winter it only had about 83 hours on it. I took it in to Odie's marine to have it checked out and winterized again so it was ready for the season. On the first trip out, the thing purred like a kitten, ran real smooth and did great. The only issue was when turning it off the motor would diesel. I took it back to Odie and he reset the timing. The next time I took it out, no more dieseling but it seemed as though the idle was set too low; it would not stay running without some throttle untill it was fully warmed up. On one trip I had spent the night in Sunny Cove. When we got up in the morning, we took off out of the cove and after about a minute or two on step the boat began to loose power and almost died. I could keep it about half throttle and it would do fine, but at full throttle it would sputter and loose power. It did this about three times and then all was fine.
I got it back to Anchorage and was going to replace the fuel water separator. I couldn't get the filter off, so I called around and took it to Boat Works of Alaska who happen to squeeze me in just in time. They had to replace the filter and housing, plus they did some carb adjustment because the idle was low. Took the boat out the next day and headed to Montague. She ran like a dream all the way out and back, however, she started to diesel again on a few occasions. The next day, we had a bunch of people on the boat, so we just took slow cruise around the bay.
Three weeks had passed and I finally got the boat back in the water this weekend. Hit Seward on Saturday morning. Launched the boat, started up fine, warmed up nicely and then headed out. Got outside the harbor and hit the throttle and it seemed like I wasn't getting enough power to get up on step. Throttled back down, adjusted trim tabs and off we went. Got up on step but still a little slower than normal, then all of the sudden, it started to loose power. After a few minutes it sputtered and died. It took a few minutes and playing with the throttle and she started again. I had to pump the throttle to keep her going and there was a weird clanking sound coming from the engine. I was able to limp back into port, and at idle the engine sounded normal and ran fine, but as soon as I tried to throttle up, it would spit and sputter.
Got back to Anchorage, hooked her up to the hose to flush her out and she started fine. However, there was a slight winning sound coming from the belt. I began to play with the throttle a little and rev her up and got it to back fire once or twice. Other than that, she sat there and idled fine and warmed up to temp while it flushed and I shut her off, no deiseling.
So here's the question. After that long story and all the symptoms, what do you suspect this could be and how would you fix it?
When I got her back from Boat Works, I was told it was time for a tune up and that the electric fuel pump was weak. I'm thinking I have some bad gas coupled with a weak fuel pump and maybe a timing belt issue. What do you think?