Evinrude 40HP – Won’t stay running in water

I’ve got a 1986 Evinrude 40HP Outboard. Idles fine in the driveway but as soon as it’s immersed in water it dies out. On the intermittent occasions I was actually able to finally get it started at the dock, it would die after applied throttle continuously for approx 5 minutes. In other words, I was able to go 25 MPH per hour for about 5-10 minutes before it governed itself down to about 5MPH then eventually shut off. I’m thinking fuel delivery issue.

I’d appreciate any advice or references to a reputable repair place is appreciated.

Forest Lake, MN area.

I had one do the same thing when I bought it.
It would idle fine but under full throttle it would bog and die. When it was doing this the electric primer would help run O.K. I cleaned the carbs with carbcleaner and it worked fine after that!

FErny

Assuming that this is a older 2-stroke with carbs, this is usually a sign that it is carb service time. Not hard to do yourself and the parts are cheap.

It is a fuel problem.. unless its overheating, or thinks its overheating and has some type of safety device to put it in limp mode.. I doubt it. If that motor has a temperature sensor, and it is pumping water.. if cleaning the carbs doesnt work, that might be the problem. If it was only doing it when its warmed up, that would be more likely… stuck thermostat, etc.. but its doing it when its cold.

It sounds to me like you might have problems with a sticky float, needle, or seat problem. If its an old fuel line it could be deteriorating from the inside restricting the fuel flow. A clean carb wont do you much good if you have little fuel line remnants blocking off the fuel flow.

Time to have the carbs cleaned and stick on a new fuel line if its old. I would guess that will take care of your problem.

If you’re able to run it for a while, try mixing sea foam with the gas. If you want to try something more agressive, try the carb cleaning instructions on the can. That stuff works wonders. Check your gas tank vent and fuel line connections, too, if you haven’t already.

That’s the lazy way to get it running well again. I bet a thorough carb cleaning and replacing the fuel lines would be a perfect fix.

Oh, and one more thing. I had a similar problem and it turned out that the fuel screen in the gas tank was obstructed. You might check that out, too.

I’ll agree sounds fuel related, is your primer bulb staying firm? My motor is really touchy to this, all other suggestions sound great

oh make sure you have the vent open on the gas tank too.

I agree on the SeaFoam. Good strong dose with clean fresh gas. If it runs, but just bogs when you give it gas I would first try replacing the primer bulb. Many times the check valve goes bad after sitting all winter. Cheap and easy to replace and it may fix the problem.

-J.

I owned an ’84 Evinrude 40hp brand spankin’ new that did the same thing. I’d take it out and after a short spurt, all I could do is idle back to the dock. I took it back to the dealer at least 4 times with the same problem and every time he’d call up and say come and get it———-just to have it do it again. After the 4th time I told him to keep it ’til it worked right. That was some time after Labor Day of that year, and I never had a chance to fish after that. Well, finally in March of the following year I called him up and asked about it. He said come up and get it. I gaurantee it will work. When I got there I saw a brand new 50hp on the back of my boat. He said that the 40 didn’t produce enough vacuum to properly operate the VRO system. That was a 1984 motor. Yours is an ’86 but the problem sounds like it could be the VRO system or the fuel system. Good luck with finding your problem. If it’s the VRO pump, you are better of disconnecting the thing and mixing your oil and fuel.

Pull apart the fuel filter screen. Had the same problem, identical about 3 years ago on a 20hp merc. Pulled apart the fuel filter screen and it was so full of sediment that hardly air could pass.

Clean that up and you will be good to go.

Update

Today, with a fresh battery, and fresh fuel… I got the Evinrude running. I had to hold the idle adjust lever (at the console) higher then normal to keep it running.

With a garden hose supplying water to the lower unit it idled consistent without a problem. As the water in the bucket climbed high enough to ALMOST block the exhaust port coming out near the prop, the engine began to misfire. I unplugged the top plug wire, I have spark to that cylinder but the idle of the engine DIDN’T change. The misfire stopped, the engine kept running even though the plug wire was disconnected. The cylinder below it continued to power the unit.

I swapped plugs & the misfire went away but by now.. the water was high enough to cover the prop completely & it wouldn’t restart. For some reason this year & last.. the engine cannot seem to function when submersed.

Yesterday I disassembled the carbs to inspect the float & the needle. Both carbs looked fine. Nothing unusual. Fuel pump pumps fuel at a consistent rate.

At idle with the top plug removed, I feel air so I know the piston is moving. Any reason why I would get fuel to one cylinder & not the other ?

Did you try the Sea foam? If not I would give it a try, my 40 Evinrude runs much better with Sea Foam.

Sounds like a bad primer bulb to me.

Hey guys !! Thanks for all the advice !! I found out some new info today.. There was 25lbs compression in the top cylinder dry & 50lbs wet. Looks like there will be an 86 Evinrude 40 horse avail for parts if anyone is interested !!