Old fuel - Vapor Lock?

[lkbum]

2001 5.0l EFI. I'm pretty sure I have a Vapor Lock issue. After shutting down, engine water gage temp has to be below 125F to start (takes about an hour to cool from 175F running temp). I have twins, both engines act identically. Fuel is about 6 months old (150 gallon tank) and I always use stabilizer (marine grade). Non ethanol 90 octane from local Marina. Never had this issue before, 2001 Chap 280 SSi. Tried running with engine hatch open and then leaving open, didn't make a difference. Fuel filters changed 3 months ago, crystal clear gas in the filter. Since both engines act the same, I'm questioning the fuel. Thoughts? Thanks in advance.

 

[tpenfield]

The fuel is probably fine, and it would not really care about the engine temp. I would check to see if the tank vent is clear and venting properly. Also the check valve at the tank fitting may be sticking.

When you say "won't start" . . . does that mean the engines crank, but won't start . . . or does the starter not even work?

 

[lkbum]

Engines crank fine, but don't start. When the engines are cold, they start and act normal. I can then run with no issues. After running for a while (long enough to reach full operating temp which is roughly 175F on my gage), if I shut down and go to restart the engines they initially start (for a couple of seconds) then "surge" momentarily and then stop. Engines then turn over, start up nd sputter on occasion but die pretty quick. If I just let the boat cool down, they start and run fine. They then operate normally. We haven't used the boat much this season. First happened going to 4th of July fireworks. 10 minutes at 3000 RPM, shut down for 15 minutes, no start (turned over, no fire) until cooled off. Last night 30 minutes at 3000, shut down for 45 minutes, no start as before until cooled off. After cooling off and restarting, they run fine with no issues at all. As long as gas is moving through the lines, no issues.

 

[tpenfield]

Another thing that I can think of is that with twins, there is 'master' / 'slave' relationship in the electronics (ECM). Possibly there could be a problem in one of the engines that is effecting both via the master/slave connectivity. Maybe some of the Mercruiser guru's (FunTimes, aChris, Bondo, et al) can comment.

Got a serial # for the engines?

 

[lkbum]

2001 models
Port serial # OMO 69661
Starboard # OMO 69669