1985 Merc 350 /260 Vapor lock

[madrussian1962]

Wellcraft Nova XL 1985 with metal fuel lines. Runs fine although I have stalling problem. I will run at different speeds with the blower on all the time and she will stall out. I wait for 15-20 minutes and she will restart and usally get me home however sometimes it will happen again and I need to wait another 15-20 minutes. I notice the Temp gage runs 200F at idle when not in motion however once under motion she will drop to 160F or below. I think I have a bad impeller in the lower unit that woud explain this however any ideas on why she stalls???? I have noticed fuel vapor coming from the carb and the air cleaner has shown black soot. Engine has 160 hours and look like a rebuilt or new carb was installed. Return fuel line looked plugged so I have removed this and will replace with new. Notice droplets in this hose. Fuel separator replaced and all gas removed and replaced with new. I have removed the fuel separator and did not find it full of water. Any help appreciated!!!! Love this boat as she is a tank in the water!!!!!!!!

 

[Bondo]

Re: 1985 Merc 350 /260 Vapor lock

I think I have a bad impeller in the lower unit

Ayuh,......... I Agree......

Return fuel line looked plugged so I have removed this and will replace with new. Notice droplets in this hose. Fuel separator replaced and all gas removed and replaced with new.

Your motor Doesn't have a Fuel Return Line....................

That's a Safety Vent Line for the Fuel Pump.......

If there was Gas in it,....... Your Fuel Pump is Bad,+ needs Replacing.......

 

[madrussian1962]

Re: 1985 Merc 350 /260 Vapor lock

Appreciate correction and advice. New OLD boat that needs some attention but cleaning up well and sound. Bought her on the water and purchasing a trailer to pull. Gimbal bearing,Impeller,Thermostat replace. Check timing, carb settings, gap etc. Any other checks or replace??? Boat has sat for 10 months.

 

[achris]

Re: 1985 Merc 350 /260 Vapor lock

As my friend Bond-o has stated, the clear/green line from the fuel pump to the air horn of the carb is a saftey hose. If the fuel pump diaphram starts leaking then the fuel is pumped up to the carb, flooding it and stalling the engine. If it didn't do that, then the fuel from the failed diaphram would go into the engine sump, turning your nice friendly engine into a bomb, a BIG bomb!!! Not a good look....

If there's fuel in the line, replace the pump (or a new diaphram kit), just do it quickly, please...

Chris..........

 

[Coors]

Re: 1985 Merc 350 /260 Vapor lock

And I ain't gonna get hammered about the statement "factory manual".

 

[Don S]

Re: 1985 Merc 350 /260 Vapor lock

And I ain't gonna get hammered about the statement "factory manual".

Then don't keep bringing it up..................

 

[madrussian1962]

Re: 1985 Merc 350 /260 Vapor lock

Thanks for all the help. I thought I had this nailed when I realized I had a stuck Thermostat. Engine wll run at 165 F or lower at all speeds NOW so I believe the lower impeller is OK and thought VAPOR LOCK was no longer the issue. Took her for a hard drive ( ran at about 4000RM GOOD POWER) over rough water and ran great for 15 minutes or so then again died. Motor hesitates then I bring her to idle and she will run for a few minutes before totally cutting out. I will sit for 15-20 minutes and she will restart and and run however on my way back after about 7-10 minutes ( ran at about 3000RPM) she died again. Sat for another 15-20 minutes and restarted fine and IDLED home with no problems ( ran at about 1100RPM). ANY THOUGHTS OR IDEAS APPRECIATED IN ADVANCE!!!!!

 

[madrussian1962]

Re: 1985 Merc 350 /260 Vapor lock

Thanks for all the help. I thought I had this nailed when I realized I had a stuck Thermostat. Engine wll run at 165 F or lower at all speeds NOW so I believe the lower impeller is OK and thought VAPOR LOCK was no longer the issue. Took her for a hard drive ( ran at about 4000RM GOOD POWER) over rough water and ran great for 15 minutes or so then again died. Motor hesitates then I bring her to idle and she will run for a few minutes before totally cutting out. I will sit for 15-20 minutes and she will restart and and run however on my way back after about 7-10 minutes ( ran at about 3000RPM) she died again. Sat for another 15-20 minutes and restarted fine and IDLED home with no problems ( ran at about 1100RPM). ANY THOUGHTS OR IDEAS APPRECIATED IN ADVANCE!!!!!

 

[madrussian1962]

Re: 1985 Merc 350 /260 Vapor lock

Thanks for all the help. I thought I had this nailed when I realized I had a stuck Thermostat. Engine wll run at 165 F or lower at all speeds NOW so I believe the lower impeller is OK and thought VAPOR LOCK was no longer the issue. Took her for a hard drive ( ran at about 4000RM GOOD POWER) over rough water and ran great for 15 minutes or so then again died. Motor hesitates then I bring her to idle and she will run for a few minutes before totally cutting out. I will sit for 15-20 minutes and she will restart and and run however on my way back after about 7-10 minutes ( ran at about 3000RPM) she died again. Sat for another 15-20 minutes and restarted fine and IDLED home with no problems ( ran at about 1100RPM). ANY THOUGHTS OR IDEAS APPRECIATED IN ADVANCE!!!!!

 

[Coors]

Re: 1985 Merc 350 /260 Vapor lock

Did you replace the leaky fuel pump?