fuel odor after WOT volvo penta

I have a '96 bowrider with a volvo penta 5.0 FI fuel injected motor(302 ford). It starts and runs good, but when I give it 3/4 to full throttle for a little bit, then take it back down to 1/2 throttle, I can start to smell gas in the passenger compartment. I cannot see any fuel leaking anywhere in the bildge or engine compartment. I took the little gas tank access cover off a couple time right after this and smelled the hoses next to the tank and could not smell and gas odor at all.

It will sit and idle without this smell and run under 2500rpm with no smell either. Seems like I only get the smell when only when doing a hard run, then backing down to idle, or backing down to half throttle.

I checked fuel tank vent, no obstructions. Gas is fresh, fuel filter is new. Engine runs strong and gets to RPM fast and boat runs fast like nothing seems to be wrong. Boat gets good gas mileage, and has not changed.

It does sometimes stall after running the motor hard then sitting idle for 3-5 minutes. Most every time it will start right up, sometimes it takes a couple cranks. When starting cold, so far never have had a problem cranks right up on first try.


Thanks for the help!!

Re: fuel odor after WOT volvo penta

How long does the smell linger? Is it more like the raw gasoline smell you would get from a gas can spillage? Or is it more like too rich exhaust fumes smell?

If it blows away soon after stopping and is like rich exhaust and not so much like raw gasoline then you may be experiencing the Station Wagon effect. A boat's basic aerodynamics will want to draw exhaust fumes back into the boat. Even an EFI engine will run slightly rich in a boat to keep chances for detonation down, they also do not run as much timing for the same reasons. This results in not-quite-so-efficient combustion and could result in that old-timey gas smell from a rich engine's exhaust. When backing down it may also richen up some as all the electronics catch up to the conditions.

If it lingers a bit even with the wind blowing and is more like the raw gasoline smell then it is probably a hose somewhere. The big hose from the fill cap to the tank can hide problems for a while. It may not leak after filling but if the same gas smell is present in the cockpit right after filling then that hose may be leaking vapor. Could be the tank vent plumbing as well.

I know you have mentioned most of these items but it is more than likely something you have already checked. Gas fumes are strong and do not require a lot of spillage, for example, put a gas can that you spilled some gas onto into your car or minivan or truck cab and even if you wiped it down good it will stink up the place in no time without ventilation.

Re: fuel odor after WOT volvo penta

Thanks for the reply, It seems to linger for a few minutes. It does smell like raw gas, but I was thinking it could be raw gas from the exhaust like you say.

It seems like I can cruise at around 3000rpm or less and not have the smell, but when I give it WOT for alittle bit, then throttle back down to 3000rpm or goto idle, I can smell the gas fumes. It does seem to go away after sitting for awhile.

Also doing sniff test through the gas tank access hole and sniffing all the hoses, I cannot smell any fumes.

Thanks for the help!!

Re: fuel odor after WOT volvo penta

I would like to give an update incase anyone else has simular problem. I had my boat in the drive to try and diagnose problem. I turned key a few times to prime the pumps, and then I felt around the fuel lines checking for any leaks.

I found a wet line that was going into the high pressure fuel pump. I screwed the brass pressure fitting until it was tight and primed a few more times and it stayed dry. I then ran on muffs for about 20 minutes and kept checking all of the fuel lines. Everything seemed to stay dry.

Hope this was my problem, thanks for the help and suggestions.