1977 mercury 140 issue

[GavinMcGraw]

Hello, new to this forum. Was hoping someone with some older Merc knowledge can help me. I have a 1977 Merc 140 tower of power. Starts great and runs good but lately I’ve had an issue when throttling up. When I go to WOT it stays at low RPM and sort of bogs. Then maybe 10 seconds of this and it finally opens up and runs great. Then if I turn it off and start it up 10 min later and try the same thing, it only happens half of the time. To sum it up, the throttle response is poor but when it does finally get going it purrs. I changed the fuel filter and that helped but still does it some times.

any ideas what I should fix? I was thinking spark plugs or maybe a carb clean.

thank you

 

[Chris1956]

Just so you know, Merc did not make a 140HP inline 6 in 1977. They made one in 1978 and 1/2 of 1979.

They also made a 140HP IL6 in the early 70's.

Check the fuel pump diagham. If it has a pinhole leak, raw fuel will get into the crankcase causing the motor to bog on acceleration. Rebuild kits are cheap and easy to install.

If that doesn't fix it, you may have dirty carbs. But the fuel pump is more likely, and a whole lot cheaper and easier to rebuild.

 

[racerone]

Try opening SLOW SPEED mixture needles 1/8th turn at a time.----Often that " no money spent " procedure cures the bogging.

 

[Chris1956]

I gave slight mis-information. Mercury made a distributor ignition 140HP motor in 1978 and 1/2 of 1979. The made a ADI 140HP IL6 motor in 1/2 of 1979 and 1980. They may have made a 140HP motor in 1981 and 1982 as well, but I am unsure.

All of these motors had the same powerhead as the Merc 1500 motor of 1976 /1977..

 

[GavinMcGraw]

Okay thanks, I’ll have to look up the serial number to find the exact year.

I’ll try and find where the fuel pump is and take a look. Would make sense it’s the fuel pump though as it ran bogged for 20 minutes as I limped it back to the docks. Clogged fuel filter.

thanks

 

[GavinMcGraw]

So I inspected my fuel pump visually and I noticed a hose clamp that was completely broken on one side and a possible small leak around the housing joints where the gasket should seal. I’m new to the boating world but I’m assuming this would be causing my hesitant acceleration problems. Does anyone know where I can buy parts for this? I figured out it’s a 1979

thanks for all the help.

 

[Chris1956]

Fuel pump rebuild kits are avail from many sources on the web. I expect there is a choice between OEM, GLM, Sierra and maybe some other brands. They will come with a new screen, oring, two gaskets and a diaphragm.

Replace the check valves and their gaskets if they look bad.

Check the two pulse lines for kinks, raw fuel and wear. Sometimes they have springs inside them to keep them from collapsing under the vacuum pluses.

I had some trouble with my fuel pump on a motor like yours. It didn't want to pump enough. So makes sure everything is clean and tight.

 

[Chris1956]

Sorry, ebasicpower, crowleymarine, Amazon and a host of others should have the kit. Likely iBoats has it too.