1990 Mercury 40 HP 4 Cylinder 2 stroke

[russwick]

Wondering if anyone has dealt with my current problem. Last week I took it out, and on the way home, the motor cut out at full throttle. Was able to drive in at about 5 MPH, spitting water from the tell tale. Did not feel hot when I put it on the trailer.

Saturday I put a new rectifier in it, as it was not charging at the battery. Compression was 150 pounds at all 4 cylinders. Spark looked good at all four plugs.

Well, yesterday I took it out, and was good at full throttle for about 15 seconds, then it cut out again. Shut it down while fishing. Started it up and again made it back at 5 MPH.

Any ideas? Thank you.

[teamlund]

Is the primer ball staying hard? If not change that and possibly any other connections that could go bad from the tank to the engine...Start off with the easy stuff.....Possibly bad gas also, I would try filling it up at a diff station..

[denpat]

I have a 1990 Mercury 100hp that was doing the same thing. It would come out of the hole very well, but after about 15 seconds at WOT it would start surging. I discovered a bad fuel line from the tank to the splash well. It was old, cracked, and must have had a hole in it some where. Had already replaced the gas line and primer bulb from the spash well to the motor, just didn't go far enough. Replaced it and now it runs perfectly.

Good luck.

[staylor]

...the previous posts about the fuel tank and lines and bulb are the first place you should start- along with a possible clogged vent in the fuel fill cap. If the motor has a fuel connector that twists on at the motor you can check everything from the tank to the fuel pump at once by just hooking up a second remote tank and another hose and bulb that you know are good. If you can't do this then put on a new hose and bulb- connect right to the tank, skipping the possible little in line metal surge valve that may be clogged. If it still acts up trying hitting the chokes and see if it speeds up from 5 mph. If the choking doesn't help, then try squeezing the bulb while its running bad and see if it speeds up. If it does run better under either of these tests then you need to clean the fuel filter or carbs or put in a fuel pump kit. If it still runs bad I'd get a dealer to check out the powerpack and coils which may be breaking down only when under load. When the rectifier crapped out it may have screwed up the powerpack or a coil/coils.
Doug

[russwick]

Thank you for all the replies. I believe it was in the fuel. Fuel Pump and fuel filter had all kinds of crud in it, so I rebuilt the pump and replaced the filter. Flushed and cleaned the tank. Took it out Saturday, and all was well. Except for a fuel leak. That is around the filter, cable tie must not be tight enough. Thanks again.