1986 Mercury Classic fifty 45 HP problem

[zapped77]

I have a used 45 HP mercury classic fifty outboard that I picked up last month (6-21-07) and running it on the hose it started and ran great. First trip out it ran great in the no wake zone hit the gas and it ran great for 30 to 60 seconds just fine and then it started reving up and down just like going from idel to full throttle over and over.

Then I pumped the gas line bulb and it would come back to life as long as you pumped the bulb. I figured bad fuel so I removed the carbs drained all the fuel and drained one tank (the card kits needed to be ordered). With new fuel and all the water cleaned out it ran good for five trips, about 20 gallons of fuel then it started doing the same thing.

I rebuilt the carbs, new fuel lines inside the motor, new hose from tank to motor, new fitting on tank. This motor has carbs with the fuel pump attached to the carbs so fuel pumps are new.

I removed the carbs one more time to check the vacuum port one each carb and when the motor cranks over the vacuum is working you can feel the air coming in and out. I reinstalled the carbs when for a test ride and the same problem but if you pump the bulb it will run just fine.

Any help would be great.

Thanks
Zapped77

 

[Laddies]

Re: 1986 Mercury Classic fifty 45 HP problem

You either have a vacume leak in the fuel line or the pumps are acting up

 

[zapped77]

Re: 1986 Mercury Classic fifty 45 HP problem

both fuel pumps are new they are attached to the carbs and I have all new gaskets for the carb mounts. where could the vacuum leak be? and all fuel lines are 100% new this is including the fitting in the tank and lines feeding in tow the tanks runs the same on both tanks.

one thing I am going to try is the fitting on the tank, the fitting is a johson type and maybe it is not letting enough fuel to pass. I know merc tanks have a different fitting. but it did run ok for a few trips that.

this morning I changed every fuel line and it still ran the same when I took it out.

let me know if you have any other idears.

thanks
zapped77

 

[Laddies]

Re: 1986 Mercury Classic fifty 45 HP problem

OK!

 

[jimmyb1966]

Re: 1986 Mercury Classic fifty 45 HP problem

Hi I was wondering if you still had your 45hp classic 50? I have one myself and am having same trouble as you did.Were you able to fix it?What I know about outboards doesnt fill a very big book but I think I could put a fuel pump kit in if I had some kind of directions and diagram.Would this come with the kit couse I have no oners manual but would like to get one.Is there one or two pumps on these?

 

[imported_Voyager]

Re: 1986 Mercury Classic fifty 45 HP problem

What rpms are you running?

The fuel pumps on these old motors are marginal. I had the same issue when my boat was loaded and the rpms were down a bit, re-propping to get more rpms at WOT fixed the issue. The mercury fuel fittings (buy the real metal ones) flow more freely than the johnson fittings, and a good quality bulb is important as well.

Also, I hear that there are new plastic (rather than rubber) fuel pump parts, but I still run the rubber gaskets.