Fuel supply on a 1981 Merc 50 pull start.

[madgadget]

Hi all,

I just picked up a merc 50hp pull start. I was told by the prev owner that he could not get it going, nor could the people at the marina he took it to. However the previous owner to him promised that it was a runner, so I did some checks and decided to take my chances. (It has compression and spark)

So I took it to my workshop put it on a stand fixed the pull start, pulled all the plugs and sprayed in some fuel, put plugs back and gave it a tug, it started and ran for about 3 seconds before dying. (I didn't hook it up to a fuel supply.)

So it runs. I then went to look at the carbs and followed the fuel lines. It goes from the intake fitting, directly over to the intake to the carbs, there is no fuel pump. Is this normal? Surely there should be some kind of pump on it somewhere?

This is where I throw it out to the experts here. Is the supply tank supposed to be pressurised by crankcase pressure to force fuel to the carbs or is there some other way this is supposed to work?

Thanks

 

[Barnacle_Bill]

Re: Fuel supply on a 1981 Merc 50 pull start.

Yes you should have a fuel pump. It may be part of the carb on that motor.

 

[madgadget]

Re: Fuel supply on a 1981 Merc 50 pull start.

Hmm ok, I couldn't see how it could be mechanically connected to anything. I shall take another look later.

 

[emckelvy]

Re: Fuel supply on a 1981 Merc 50 pull start.

Lots of later-model Mercs had fuel pumps integral with the carburetor. Find the serial # on your transom clamp and look up parts diagrams for your motor here:

http://www.mercruiserparts.com/SelectModelType3.asp?class_id=2

Also see this FAQ section which has tons of good general info about 'waking up' a 'sleeping' motor, and troubleshooting techniques:

http://forums.iboats.com/forumdisplay.php?f=31

HTH............ed

 

[madgadget]

Re: Fuel supply on a 1981 Merc 50 pull start.

Well I have a serial number of: 9341626 (Europe model). Its a 50HP model 4cyl. This seems to fit though: 9107214 THRU 9248005

And specifically:

But I need to go to workshop tomorrow and check.

Thanks for the info I'll rip one of the carbs off and see what's going on in it!

Ed

 

[emckelvy]

Re: Fuel supply on a 1981 Merc 50 pull start.

Pull the bottom bowl on that carb and if you see a lot of Green Stuff in the jets you've likely found the problem.

In that case, be sure to clean out both carbs and blow out with compressed air or at least carb cleaner if you don't have a compressor. You may have to remove the jets/orifice tubes and mechanically clean to get the junk out, if it's badly caked....ed