85 1977 mercury bogs at half to wot but idles ok. Need to pump bulb to keep running.

[andrewbabich]

85 1977 mercury bogs at half to wot but idles ok.

The boat starts right up and get right up on plane, but soon it starts bogging down and sounds like its about to stall. So my buddy sits at the back and needs to pump bulb to keep running. We give it a pump... oh about every 10 seconds i'm guessing.

I suspect fuel pump needs a rebuild or air in the lines, but before I try and rebuild the fuel pump, is there a clear check tube near the fuel pump I can check for bubbles or something like that, i read that there might be one?

I 'm having trouble finding any serial number on this old motor to even order a fuel pump. Where should I be checking for the serial number.

Thanks
Drew

 

[Chris1956]

Re: 85 1977 mercury bogs at half to wot but idles ok. Need to pump bulb to keep runn

Serial number should be in center of transom clamp, between the clamp screws.

There is no factory clear tubing that you can find on that motor. A rebuild kit for the fuel pump is real cheap. I would just rebuild it. You can order them from a local Merc dealer, iboats, ebasicpower, crowleymarine, Dougrussell etc. You will need to know the year exactly as there are some differences in fuel pumps.

 

[andrewbabich]

Re: 85 1977 mercury bogs at half to wot but idles ok. Need to pump bulb to keep runn

I found the serial number : 4723613. I think the motor is a 1977. I found a rebuild kit on ebay for this that includes this serial number so I'm going to go for it.

Some diy website recommended installing a clear fuel tube in between the fuel pump and carbs to see if you have any bubbles going to the carbs. Anyone recommend or have experience with this type of diagnostic procedure.

My fuel line from the pump to the carbs goes behind the electrical panel and the starter so it looks like a pain in the butt to get to...

I would like to see if my fuel has bubbles in it. I have replaced the primer bulb line and have a newer 6 gallon tank threaded into one end of that line, but its possible air is getting in by the threads on the 6 gallon tank.

 

[Chris1956]

Re: 85 1977 mercury bogs at half to wot but idles ok. Need to pump bulb to keep runn

The clear fuel line could be installed between the bulb and the quick connect fitting at the motor. Or it could be installed from the quick connect to the fuel pump. You will find that you can get at the pump to carb fuel line real easy once you have some experience on the motor.

 

[kevblac]

Re: 85 1977 mercury bogs at half to wot but idles ok. Need to pump bulb to keep runn

I saw your thread in Iboats about your engine, I have the same engine and the same problem. Did you ever find out what was going on. I need some help. If you got yours running I would sure like to know what the problem was.....Thanks my email is kevinfblack@yahoo.com

 

[carholme]

Re: 85 1977 mercury bogs at half to wot but idles ok. Need to pump bulb to keep runn

Drew;

Yes, your s/n comes up as:

85 850 4-cyl 4590512 4831998 1977 USA

From here:

http://www.marinshopen.se/Motorer/O...Mercury2takt4cyl4085hp/tabid/487/Default.aspx

Parts listing:

http://www.crowleymarine.com/mercury-outboard/475.cfm

Service Manual: 90-86134--4

or you can download this condensed version of the Clymer manual:

http://web.ebscohost.com/serrc/pdf?sid=91f5cc4f-7643-4e96-99b1-94d06753e929@sessionmgr4&vid=4&hid=13

Gerry