Engine dies out when loading boat onto trailer

My 1992 60 hp mercury 2 stroke runs like a champ on the water for its age. The engine fires up on the first turn of the key every time and runs great all day but my last 3 times out only when I load the boat onto the trailer she dies out, almost like when the engine feels resistance. I then start the engine up again and give her gas and she quits again making me jump out of the boat and into the water and use the winch the rest of the way. Anyone ever come across this problem or know why this is happening. This never was an issue before. Thanks 

Needabiggerboat I replaced the primer bulb and line and now waiting on a new fuel filter so we will see how it goes after that. I will update once I get the boat back in the water. Master _Piker I will try the flip up the warm up lever to see if that helps. Thanks

One thing that would help my old motor is before driving up the trailer, I would flip up the warmup lever for a few seconds. This would burn any extra fuel out of the cylinders and prime the fuel lines. If I was night fishing, I would often skip this step and just crank the boat up the trailer as revving the engine at the launch late at night could disturb the residents on the lake. Try that and see if it helps next time.

Needabiggerboat,

I am guessing it has something to do with the load the engine is under when trying to push your boat up the trailer. You cannot simulate that in the driveway with muffs as the prop is not pushing anything but air. Even your idle RPM's will be a little higher than when the motor is in the water due to the lack of back pressure from the lower unit being submerged. Power loading your boat is like starting a manual transmission vehicle uphill in 2nd or 3rd gear from a stop sign. If you have a powerful enough engine, it can work, but if you are running a smaller hp engine, it will bog out and die. When you go to plane your boat, you can spool up the engine gradually without trying to push the boat 'uphill' on the trailer. There is a lot less force required. Those engines are 20 years old and carbed. EFI or DFI is a whole different ballgame. I had a 70hp Evinride VRO that would do this. If I slammed the throttle down quick, I could drive up the trailer, but if I did it gradually, it would bog down. The marina told me that at low RPMs with a carbed engine under a heavy load, the fuel mixture would get super rich and basically flood the motor out. It was like choking the motor. I just dealt with it. The motor started easily and ran fantastic on the water, so I never messed with it.

GotABite – did you find a solution?  I ask because I have a similar problem with my 1999 Mercury 50 HP, 2 stroke, 3 carbureted cylinder motor.  It occasionally suddenly dies when power loading on the trailer.  Besides that, it still runs like a champ.

Stuff I have ruled out:

• Same ramps and trailer as before
• Problem occurred with multiple tanks of gas, usually fresh, always with seafoam.  No fuel or any problems when the engine is running on the water (any RPM, any trim angle)
• Fuel filter was replaced (no help, had insignificant debris)
• Primer bulb, hose and connection all look good
• Electric connections seem secure – kill switch OK.  Engine restarts OK.

Tests completed:

• Tried to replicate the problem on an inclined driveway with earmuffs.
  • Could not replicate at any angle
  • Disconnected fuel hose from engine, there is enough full on engine lines for it to keep running for about minute.  Conclude problem in under engine cowling.  At ramp, the engine dies quickly, no sputtering.  

I hesitate to open it up to look at the carbs.  Outside looks very clean.  Could it be stuck a float from overdoing the fogging in the fall?   Any feedback is appreciated.

Banjo dan not sure on how many carbs on the engine. I don't know much about them.

FUEL FILTER CLOGGED

I think Finbender has solid advice too, especially about the connection of the fuel line at the engine. The connection might be fine when the engine isn't trimmed-up because there's no extra fight against gravity, which might explain why you can run it all day just fine, but not fine when trimmed-up at the launch. 

If that connection is lousy, or the check valve inside your primer bulb wore out - very common - that would make sense. Trimmed-up, gas just falls back down and the pump isn't strong enough to overcome it.

How many carbs on your engine?

Thanks Finbender! will check all three.

Here are the things I'd look at first, in order:

1) bad fuel

2) air leak (bad o-ring) at fuel line to motor connection

3) compression test

Good Luck.

Thanks hunt fish, I use Startron but I have to admit I use  87 octane so I should prob switch. 

You stated it seems to happen only when you tilt the motor at the landing, Otherwise it runs fine. I believe Banjo has some good advice regarding cause. Make sure you use premium gas and use Seafoam to clean things along the way for good maintenance.

Thanks banjo dan i will give it a try.

If you can repeat the problem away from the launch, then it seems to me like the trimming is related to the issue. As a mechanic, 2014Ranger knows more than me and can double-check my thinking, but if trimming is the problem, then I'd probably check for a sticky float and/or needle valve in the carbs, which is pretty simple. 

(And then I might as well clean the carbs and get new gaskets if anything looks crummy because I'm already in there and it's cheap and easy, and needs to be done at some point anyway.)

I'd also try to repeat the problem away from the launch, but instead of trimming up while in neutral, try trimming up while in gear and at idle, and then give it some power and see what happens.

I did not get a new vehicle banjo dan but yes I will try that out next time on the water.

Did you get a new truck by any chance?

If it were my boat, the first thing I would try, is to see if I could repeat the problem, but not at the launch. In neutral, trim up the motor to about the same position as when loading, put it into gear, and give it the same amount of power and see what happens. (Even better, I'd get a couple of my heaviest friends in the boat.)