Mercury 50hp troubles

[TACOMATruckin98]

Hey guys, first post, first real trouble with a boat. We recently purchased a pontoon with a 1965 Mercury 500 o/b. The trouble im having is very strange. I got the motor running after sitting over a year. Sitting in the yard, it runs, starts, does everything no problem whatsoever. Yesterday, took the boat to the lake. Put it in the water, starts up very well. Let the boat idle for 5-10 minutes, put it in gear to go to the dock, and the boat completely bogs out. I can't move the warm up lever away from warm-up much, if it all without it bogging out and dieing. When i go to the motor, the fuel bulb is completely limp, and finally it wont start at all, and run down the battery. Go to pull the cover off and it sparks at me. Im totally confused whether its fuel, or ignition. It doesnt make sense with it running perfect out of the water, and like crap in the water. Any help would be GREATLY appreciated. Sorry for the long explanation

 

[tashasdaddy]

Re: Mercury 50hp troubles

open the vent on the tank, should solve collasped bulb. the idle has to be set higher when running on muffs, because there is no backpressure, from the exhaust being submerged in the water. thus, on muffs, set idle higher, then fine tune in the water. 650 -700 at idle in geat. as far as sparking, check for bare wires,

 

[TACOMATruckin98]

Re: Mercury 50hp troubles

yeah, i need to find out how to idle it up a little bit, and take off the cover that holds the ignition and try and replace bare wires. however, when we replaced the old dryrotted fuel line, where it connects to the engine, the fuel line part turned, however, it wouldnt come off. Having the vent closed, open, and cap off, it still had the same deal. Could it be something with where the fuel line goes onto the engine, the engine part itself? Anybody know what screw adjusts the idle?

 

[tmcalavy]

Re: Mercury 50hp troubles

Sounds like you need to check: compression, spark, fuel fitting at outboard, fuel system between tank and bulb. Check compression just for your peace of mind, all 4 jugs should be over 95 and all should be within 10% of each other. Check spark on each plug/wire by pulling plug, reattaching wire and holding plug electrode up to the block...you should get a strong blue spark. If it tried to bite you when you took the cowl off, sounds like you need to replace some of the old wiring. Use marine grade wire, the right gauge, and go slowly...replacing one at a time. If you need to replace plug wires, you want solid metal core wires...not modern auto wires. The wires on my 73 Merc 500 threaded into the distributor cap just like a bolt into a nut...yours may be the same, don't yank on them. Probably wouldn't hurt to check the points, coils, condensors...there may be an access plate on the flywheel to sight through...if not, time to pull the flywheel. Your fuel problem sounds like an obstruction somewhere between the bulb and the tank...may be some crud in the tank blocking the pickup. You should be able to turn and disconnect the fuel line at the motor and at the tank...the old fitting at the motor may be crudded up. You can find a new replacement almost anywhere that carries Merc stuff. The bogging and dying could mean it's due for a link-n-sync...getting the timing and carbs in synch...I paid about $50 to get the 73 Merc 500 done...shouldn't be much higher nowadays. The Merc 500's are really stout outboards, let us know how it goes.

 

[TACOMATruckin98]

Re: Mercury 50hp troubles

yeah, i talked to a guy that i know whos a marine mechanic, and im gonna replace the wires and probably rebuild the carbs. How do you take off the part of the motor itself that the fuel line attatches to? i really would like to get that off, and get it fixed. i have 2 merc 500s, and love them, but, this one is being a pain. just gotta get this one running right, and do some fishin!

 

[agitator]

Re: Mercury 50hp troubles

Had the same trouble with mine. Great on the muffs, good idle and stall and quit if I tried to accelerate. Clean plugs but they were defective anyhow. Try new plugs.