Fuel starving need help finding correct fuel pump rebuild kit for 1977 Mercury 1500.

[dwilley]

I have a 1977 Mercury 1500 (S/N 4750384) that is starving itself for fuel. I have cleaned the carburetors but the only way I can get it to cold start is to manual spray some fuel in the carbs. Motor has good compression on all six cylinders. It has eletronic choke on top two carbs but it won't pull any fuel when choked, anyone got any ideas why, last year I could choke a little bit and it would fire up and run fine. This year it won't start without spraying fuel in carbs and dogs and wants to die if you go past half throttle while under load, runs good on muffs. I am going to try to rebuilding the fuel pump but when I look up my motor on iboats I get the wrong fuel pump kit. Searching on other sites I believe my motor came with two different styles of fuel pumps. The one that shows up on iboats is the Sierra 18-7807 but the one I think I need is 18-7813. Thanks for your help.

 

[carholme]

Re: Fuel starving need help finding correct fuel pump rebuild kit for 1977 Mercury 15

What is the p/n of your present pump 55156A5 or 66530A2?


Gerry

 

[Chris1956]

Re: Fuel starving need help finding correct fuel pump rebuild kit for 1977 Mercury 15

My '77 Merc 1500 had the single fuel pump shaped sorta shaped like a figure 8. They were marginal IMHO. If you have the backdrag carbs, there is a small Stainless screen under the brass fittings in the carb covers. These screens can get clogged. You have to remove the brass Tee and Elbow fittings to see 'em.

Are you using max cold start lever, and choking the motor while cranking it?

 

[dwilley]

Re: Fuel starving need help finding correct fuel pump rebuild kit for 1977 Mercury 15

The fuel pump I have is the 66530A2 which is the single figure 8 shaped one. I believe I have the backdraft carbs, they have the black line on the top running from the bowl cover to the right side of the carb. I read on another thread that I should put a bb in the line but others say that isn't necessary? Seems like flow through that line isn't necessary if people are blocking the line with a bb, or are you talking about a different brass fitting? When I cleaned the carbs I didn't take out the jets, whoever rebuilt the carb last put what looks to be red nail polish on all the screws and I couldn't get them out so I just sprayed carb cleaner through the jets and blew them out with the air hose. I need to break down and buy three carb rebuild kits but haven't brought myself to do it yet, $$$. The primer bulb could be the cause of a lot of my issues. It was disintegrating from the inside and filling the fuel pump screen with old pieces of black rubber, have a new one now. Can I put a fuel pressure gauge on the fuel pump to see what it is putting out, if so how much pressure is good? I'm not sure what the max cold start lever is? Last season it wouldn't run past half throttle but it would start with the choke. I just choked it until it fired then let off the choke and it would fire up and run. Whatever was wrong last year has gotten worse. I only had the boat out twice and didn't get it fixed before the season was over. Thanks for your help.

 

[carholme]

Re: Fuel starving need help finding correct fuel pump rebuild kit for 1977 Mercury 15

Here is the parts listing for your engine:

http://www.crowleymarine.com/mercury-outboard/462.cfm

For your fuel pump, see under FUEL PUMP AND FUEL LINE ASSEMBLY (SERIAL GROUP #2)

Everything you need to rebuild your fuel pump is there. In the same drawing, see hose, item 25. Disconnect that from the upper carb and using a container to catch the fuel have someone crank the engine and check for a strong pulsing action. Quite frankly, if you have worries about the pump, the parts are cheap and I would just go ahead an rebuild it.

The service manual for your engine is p/n: 90-75512 and you would have to google to see what is available. In the interim, here is a link to the condensed version of the Clymer manual which will help you get started. Let the page load for several secdonds and download soonest to your computer as the link is short lived.

http://web.ebscohost.com/serrc/pdf?...2-a5b8-a52e2a1e704f@sessionmgr15&vid=4&hid=13

Gerry

 

[Chris1956]

Re: Fuel starving need help finding correct fuel pump rebuild kit for 1977 Mercury 15

On MerControls there is a small cold start lever. It is flush to the top of the MerControl. It is lifted up to advance the throttle for cold starting.

The main fuel jet is under a brass hex head bolt on the bottom front of each carb. Remove the bolt and give 'em a blast of gumout.
The idle restrictors are under a brass plug on the top of the carb body. These can be hard of impossible to get out. The red nail polish could be from the factory.

If your primer bulb is falling apart, replace it and clean the filter screen on the fuel pump.

Sounds like you do need to check the stainless steel screens on the carb tops. The brass fittings that cover the screens are for fuel to get into the carb. if the screens are clogged, fuel cannot enter the carb bowls.

BTW - Leave the backdrag hoses alone for now. They are not your problem.

Pump the primer as you accelerate. If that fixes your problem, it is very likely you have a weak fuel pump, clogged screens or some combo.

 

[carholme]

Re: Fuel starving need help finding correct fuel pump rebuild kit for 1977 Mercury 15

The warm up lever is item 17 in this link:

http://www.crowleymarine.com/mercury-outboard/parts/640_28.cfm

Are you sure that your electric choke is working. You should hear it click when you hit the button.

Gerry

 

[dwilley]

Re: Fuel starving need help finding correct fuel pump rebuild kit for 1977 Mercury 15

My boat doesn't have the original MerControls. They were under the seat when I bought it. The controls that are on it are Mercury controls of some kind but it doesn't have the cold start lever. Yes, I'm sure the electronic choke is working it clicks and you can see the choke flappers go over the carb throat but no fuel is being sucked up. I thought that they weren't sealing good but it looks like they are not supposed to because it has a cutout on the bottom of the flap so it can still get enough air flow. I put a new primer and fuel line on. I disconnected the main fuel line to the carbs and when I squeeze the primer bulb it gets hard with little fuel flow but if you squeeze it really hard fuel will flow through the fuel pump and out the line. With the fuel line disconnected from the carbs it should flow really easy and the primer should never get hard right? I am going to take the carbs back off and totally disassemble them and try to find the screen you are talking about. Something is definitely wrong with the fuel pump or my new primer is no good.

 

[dwilley]

Re: Fuel starving need help finding correct fuel pump rebuild kit for 1977 Mercury 15

Here is a picture of my carbs I stole from another thread. If I remember right they are WMK-22 models. Are these backdraft carbs. Where is the screen you are talking about?

View attachment 150675

 

[dwilley]

Re: Fuel starving need help finding correct fuel pump rebuild kit for 1977 Mercury 15

That didn't work try this.

 

[Chris1956]

Re: Fuel starving need help finding correct fuel pump rebuild kit for 1977 Mercury 15

Those are backdrag carbs. You see the brass elbow where the fuel line connects? Remove the brass elbow to see the screens. BTW - that carb has had the backdrag jet removed. The backdrag function is therefore inoperable.

 

[dwilley]

Re: Fuel starving need help finding correct fuel pump rebuild kit for 1977 Mercury 15

I finally got to take the boat out today. I have rebuilt the fuel pump, cleaned the carburetors, replaced all the fuel lines including the primer bulb. One thing I noticed when I cleaned the carbs the last time is that the needle valve on top of the carb floats are sticking. If you push the valve closed the needle will stick shut but open back up if you tap on the top. The boat ran good today up until about half throttle when it will fall on its face. I also noticed that the primer bulb was sucked almost flat. When I pumped the primer the boat would pick up and go full throttle for a little bit then run out of fuel and only go to half throttle again. I did find out last weekend that the new primer bulb I installed was restricting flow so I put a different one on and now it is better but still not great. Could the valve on the tank be not venting correctly allowing the primer to be sucked in. I guess I will break down and buy carb rebuild kits or at least new float needle valves and seats and see if that helps. I ran the motor with the fuel pump pulling from a bucket and it had tons of flow. I still think the primer bulb isn't allowing enough flow. Anyone have any advice? Thanks.