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30 4cyl merc engine Trouble running

D

Dan Hutchings

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"Ok here's the problem. I

"Ok here's the problem. I have been running my 1991 Sea Ray once a week for the past four weeks. The last time I took it out I have had a problem. It will run good for a about 10 minutes at full speed and then will bog down and die. It will not restart until it sits for 15 minutes then it will restart and run for about 10 minutes and die. The problem is intermittent. The engine is not overheating. Prior to this problem I filled up the tank, and ran the gas stations pump dry. I have replaced the water separator, Fuel pump, in-line filter, coil, plugs, points, distributor cap, condensor, adjusted the carb, and checked the timing. I have taken it out on test runs and it will run great for about 10 minutes and the problem would start again. I have not solved the problem and I'm completely stuck please help."
 
"Check the vent screen in the

"Check the vent screen in the gas cap. If it's clogged, the fuel pump will draw a vacuum in the tank. Eventually, (10 minutes or so, less time if the tank is near full), the pump will loose suction head."
 
Thanks Troy no such luck there

Thanks Troy no such luck there is no screen in the gas cap. I even checked to buy a new and they didn't have a screen either. I did change the water separator again and that still didn't work. Anybody else any suggestions???? Please help I don't want to take it to a shop.
 
The fuel tank is vented. I che

The fuel tank is vented. I checked that and I took the gas cap off once it died to see if it was the fuel tank not being vented. Thanks for your help. Still stuck.
 
"I'll bet you have a fuel

"I'll bet you have a fuel FILTER (not STRAINER) before the fuel pump? If so, it is strangling the fuel pump, which simply allows your carb to go empty after a hard run (since the pump can't keep up).

Case in point: My old 28 Bayiner did the exact same thing. Previous owner installed a second fuel FILTER before the electric pump (while leaving the strainer in place) . When that filter was tossed out, leaving the STRAINER in place (along withthe filter AFTER the pump), the problem went away.

Here's the deal: Gas vaporizes easily, so a pump can't suck it in through a strong resistance (like a filter before the pump). So it vaporizes, and pumps don't pump vapor very well (nor would the motor run on it anyway).

Jeff

PS: A strainer removes big chunks to protect the pump/ a filter removes tiny particles, to protect the carb. You need both, but put only stainers BEFORE the pump."
 
I do have a water separator be

I do have a water separator before the fuel pump but I have changed that filter twice now. Other than that I don't have anything before the pump. I have ran the boat for several weeks with the water separator on it with no problems. Do you think it is the water separator causing the problems?????
 
Do you think I should re-run t

Do you think I should re-run the separator so that it is after the fuel pump???? If so what about running a rubber line into the carburetor cause I have a metal line right now running from the fuel pump to the carb???
 
You might try by-passing ther

You might try by-passing ther separator as an experiment. Don't leave it out if that's not it.

You also might have a weak spring in the fuel pump. That can be checked by installing a 0 t0 15 psig pressyre gage after the fuel pump and eyeballing it during a full throttle run.

Jeff
 
Ok by-passed the water separat

Ok by-passed the water separator and not too much luck it was a little better. It did die on us but we got a longer run out of it. I took the fuel line off from the fuel pump a blew back into the fuel tank and there was a lot of pressure there. I would hook the line back up and it would run again for a little. I think something is clogging up in the fuel tank so I am going to take the tank out on Tuesday and have it flushed out. Hopefully that will work. does that sound like it might be the problem??????
 
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