'77 Mercury 850 fuel pump issue

Bradmph

Bradmph

Cadet
Joined
Aug 30, 2009
Messages
24
I think I am having a fuel pump issue with my '77 850 thunderbolt. I can squirt fuel into carbs and the boat starts right up, runs for about 20 seconds and stops. I removed the fuel pump and the filter was clean and the diaphram was ok, though it was a little bit stretched from the pressure put on it by this springed cap that was located against the diaphram. This was centered right in the middle of the diaphram and the cap on the spring was about a 1/2 in. in diameter. I could not locate this spring and cap part in a parts list to rebuild the pump anywhere. Is this part supose to be there or not? This spring is pretty stiff also, though it does not look bad.

I included a picture of the parts in my pump and I also created an image on this picture showing the spring and cap that was found in the pump.
850pump.jpg
 
Wingedwheel

Wingedwheel

Lieutenant Junior Grade
Joined
Jun 16, 2009
Messages
1,071
Re: '77 Mercury 850 fuel pump issue

Was it located by the check valves? or between the diaphram and check valves? I'm trying to remember if there was one inside my fuel pump when I rebuilt it as I have the same motor. Perhaps it helps regulate the pulses from the engine block.
 
Bradmph

Bradmph

Cadet
Joined
Aug 30, 2009
Messages
24
Re: '77 Mercury 850 fuel pump issue

I was searching the web and I finally found a kit that contains the part. The kit is called a check valve kit and it can be viewed at this link...
="http://store.eastcoastmarineservice.com/ProductDetails.asp?ProductCode=21-30430A13"

The spring and black cap that fits on the spring is shown in the pic.
Location was between the check valve and diaphram.
Have you heard of anyone replacing this kind of pump and installing an electric pump in it's place? This motor I have has been a problem for a while now. It is very hard to get started unless I prime the carbs with a bottle and when I return the warmup lever to home for idle it stalls. It will run ok with a hose on it in the driveway after cranking it over for a long time, but at the lake it will not even make it in gear before she slowly idles down to stall.
I do have to manually choke it right now until I can find a replacement choke solenoid. After idleing for a while and shutting down, I have to choke it again and again. I figured an electric fuel pump with a manual flow restrictor would cure this stalling since I just about done everything I could to fix the problem, yet it still exist.
 
You must log in or register to reply here.
Top