Optimax 150 fuel leak

[dave115]

Guys I have an intermittent fuel leak that I cannot find and hoping someone can help. It is a 2010 non-XS Optimax. Model no. 1150D73HY serial no. 1B776244.

When the leak occurs there is a slick and fuel odor on the water. I had previously thought it was unburnt fuel from the exhaust but I trimmed the motor up on the water last time it happened and found fuel was dripping out of the lower cowling. Was mostly from the starboard side but could have been just because I was on that side and the boat was listing a little bit. I do not know if it had oil in it, only that it was definitely fuel.

I took the lower cowling off the next day and ran it on muffs and no leak could be found. Nothing at either fuel rail or around the fittings on the vst. No fuel remained in the cowling but there was slight fuel odor on some residue at the bottom of the starboard lower cowling (as expected).

I have only had this happen after a long run and it only seems to occur (or at least is more noticeable) in cooler weather. It runs fine except that it does have an occasional rough idle in hot weather but always runs fine at speed. I know - a rough idle in hot weather and a fuel leak in cold weather. Awesome.

Water separator and fuel filter were just replaced and the shop didn't see any leaks then (had this issue prior to that work so the leak is not related to the filter change).

Bottom line is there any condition where a fuel leak inside the cowling would only occur during a high speed run and not at idle, and if cold conditions could exacerbate it?

If I take it in I am afraid the shop will idle it on muffs and not find any leak, hoping to find a place to start.

Thanks in advance.

[EuropeanAM]

Start it with the cowling OFF when it's stone-cold the first time of the day and monitor the bottom of the STB side fuel rail, as well as all hoses/connections.

Moving your post to the 2.5L Forum (correct place).