1975 115hp Merc

[utfyrfytr]

Hi guys, Took my 75,115hp Merc out for the first time last week and this is on a 1968 Crestliner that I have been redoing for the past year. The motor is new to me and has many new parts and has been rewired. It ran fine most of the morning and we even trolled with it for about an hour. After a short run across the water it was idling fine but when I went to give it more throttle it just died. It would restart but not accelerate so we idled over to another spot and fished for about 30 min and then tried it again. This time I move the cold start lever to a faster idle and started the motor. When I put it in gear it stumbled for a maybe 2-3 seconds and then took off and ran pretty well back to the docks. It is a 17' with a bow tank and so due to the distance (20 ft), I put an electric fuel pump on it when I ran the fuel line. I guess my question is it seems the problem may have been fuel related so would you think a faulty fuel pump at the engine could be a cause for the problem? It doesn't make sense to me since it has the elec pump but maybe? I tried to find a fuel pump rebuild kit here on Iboats but could not locate one. The motor serial # is 4239210 if anyone knows where I can find one. Sorry for the long post and thanks for any advise you may have.

 

[flyingscott]

This might be what you need sierra
18-7811 - Diaphragm Kit, 89031A1
21-30430A 7 - Check Valve Kit
89031A 1 - Diaphragm - Priced Individually

 

[Chris1956]

Your symptoms point to dirty or misadjusted carbs. You could have picked up some debris from the tank, while running it.

 

[utfyrfytr]

Thanks guys, the tank is new, the fuel line is new, the filter is new and I went through the carbs last winter, but that is what it acts like to me also. I could try adjusting the carbs a little and see what that does for me. I haven't looked up the parts #'s yet but I will shortly. Thanks again.

 

[Chris1956]

A typical mistake is setting the idle mixture too lean. It will cause the motor to bog or stall when trying to accelerate. Richen the mixture 1/8 turn (top carb first), and see if performance improves. Follow with mid carb, then bottom carb. Test after each adjustment. Remember adjust only one carb and then test.

 

[utfyrfytr]

Thanks Chris. To my untrained marine repair ear, (I was a small engine mechanic for a lot of years), It sounds as if it is already a little rich but I will certainly give that a try. These old Mercs are like nothing I have ever worked on before so thanks for your help.

 

[roscoe]

In my experience, if you tune to a good idle, you will be too lean, and will not accelerate. Better to be a little rich.

 

[utfyrfytr]

Thanks Roscoe, I won't be able to get it out again until after the 4th, I'll mess with it a little more then.

 

[jimmbo]

What kind of pressure is the Electric Fuel pump delivering? Too much pressure can cause a high fuel level in the carbs. Also what means do you have to ensure the pump isn't trying to supply fuel if the engine isn't running? And, here is a big one... Is the fuel pump USCG approved?

 

[utfyrfytr]

The pump specs say 2.5 - 4.5psi, the pump is on it's own rocker switch, the pump says gas, diesel, marine carbureted E80165