V-6 odd fuel issue

[studlymandingo]

I have a 1986 150HP V-6 which has recently developed a strange fuel issue. I always start the motor on muffs at home before traveling the long distance to the ramp 4 blocks from my house. Once in the water, she starts at the first bump of the key. There is a no-wake zone from the dock around a large mangrove stand and into the bayou leading to Tampa Bay. While idling around the mangroves, the motor will die; I have to pump the bulb up and restart. Shortly thereafter, I am through the no-wake zone and I can throttle up to plane; the boat runs fine thereafter until I reach my destination. At any point now, I can Idle as long as I would like with no stalling. After sitting at anchor, beached, drifting, or whatever, I turn the key and she starts immediately; however again running for just a minute the motor stalls and I have to pump the bulb.

This problem has only begun since I replaced the aluminum tank with a new poly tank (55 gallon). I ran a brand new fuel line from the tank to the water seperator at the time the tank was swapped. I have installed a new line and primer bulb from the water seperator to the bayonet connector, and I just put new gaskets and diaphragm in the fuel pump thinking it to be the culprit. I still have the issue.

The new tank is venting just fine as I can fill it faster than what the old tank would take fuel. Before this began, once the boat had been started once in the day, it would start the rest of the day with just the bump of the ignition and would not stall. This is a nuisance more than anything else, except yesterday, I took off from anchor in some pretty heavy surf as the afternoon winds had made for some pretty heady seas in the Gulf; I was without power for the 30+ seconds it took me to prime the system again.

Any Ideas as to what is causing this issue? Is there some sort of check valve in the fuel pump? Thinking it was the valve in the bulb, I just put a new one on but it didn't help.​

 

[gss036]

Re: V-6 odd fuel issue

I had the same situation w/1989 Merc 200 hp about 4 years ago, checked things over several times. The only thing I replaced was the fuel/water seperator filter and that fixed the problem. I have since tried to find filters with the rounded type gasket, almost looks like an "O ring", instead of the flat ones, thinking that they might get a better seal. That seems to have fixed my problem.

 

[CharlieB]

Re: V-6 odd fuel issue

You have a very small air leak into the fuel line.

Re-check lines and fittings, a small leak allows enough air at idle that you run out of fuel yet at speed it is vented out at the carbs, potentially dangerous as you will be running lean on the top carb and could melt pistons.

 

[studlymandingo]

Re: V-6 odd fuel issue

I checked all of the fittings from the tank to the bayonet connector and didn't find any fittings leaking. I haven't replaced the fuel/ water seperator this season. Once I have overcome the initial stall, I can idle as long as I want without it dying again. Once it has been shut off for a few minutes, it does the same thing again. I will replace the filter and recheck all of the connections; like I mentioned before, the fuel line is new all the way.​

 

[studlymandingo]

Re: V-6 odd fuel issue

I checked all of the fittings and couldn't find any indication of a leak anywhere. My fuel line runs under the deck in the netherworld, but it is brand new. I replaced the racor filter, maybe there is something with that; I haven't had the chance to test it since, but I will post my results.​

 

[DHPMARINE]

Re: V-6 odd fuel issue

It's easy to replace the anti-siphon valve on the fuel tank,and it may be your problem.

DHP

 

[studlymandingo]

Re: V-6 odd fuel issue

My tank doesn't have an anti-siphon valve. Straight shot from the pickup tube to the water seperator. I don't believe the old tank had a valve either.​