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 

2014ranger+115 , thanks for your detailed response. Appreciate the help! 

Your problem appears to be fuel related.  As a mechanic, I would suggest you either have bad fuel from not being stabilized or water in the system caused by condensation.  You may have to drain all your fuel or use it up and then drain the rest.  Get it all out.  You may be wise to fuel to put a fuel/water seperator inline.  It looks like a remote oil filter but designed to catch water.  It can be drained and used again, but shouldnt as a fuel leak can develop.  Drain your carbs.  The screw on the bottom of them will do that.  Try a small gas tank with fresh gas to confirm.  In fall I drain all fuel and put it in my vehicles.  Put in fresh fuel with a  double dose of marine Stabile.  Fill the tank all the way up to prevent condensation.  Run the motor with this fuel, prefereably on the water so the fuel reaches all parts of the carbs or injectors.  Your fuel system will now have fresh gas when you fire it up in the spring.  You can skip the seperator if you get all the water out.  You may have to drain the carbs or fuel system a couple times.  You need to start fresh and then nip it in the bud.  You may be picking up condensation a bit here and there as you use the boat and it may eventually become too much to run the motor at all.  Definitely bring along a portable tank and try it out or keep just in case.

BanjoDan it has happened in 2 different bodies of water once on a river and twice on a lake. I have a roller trailer. I keep the last roller just above the waterline and trim up engine a bit  as I have for the last 16 years with this boat without ever having a problem until just recent. Thanks

GotABite: just curious if the three times it happened were all at the same boat launch?

the responses on this post are epic, has not a damn thing to do with friction on loading...bunk or roller....his outboard QUITS....while loading...probably didn't read that part but at least you got to post SOMETHING....this place amazes me

Thanks jbuckets4 and Fv.screaming drags.com for your input. I will try both.

I agree with prop on the fuel lines. It can also depend on the resistance of the trailer ie whether it is a bunk or roller trailer I have a 93 90hp mercury on a bunk trailer and it does the same thing trimmed up and trying to load I try to back the trailer in till just the tips of the bunks are sticking out of the water to direct the bow to the winch and it helps 

Also, use Star-Tron to stabilize the ethanol in the gas tank + TWICE(!) the recommended amount of Sea-Foam motor treatment for 2-cycle i.e., 4oz/gal.

I recommend submerging your trailer more so that the motor doesn't have to work as hard to load the boat.

Thanks Propbuster.

I have a 2005 50...imagine your 60 is basically the same with the carburetors in the front?

I replaced the whole fuel line (and) the pick-up tube assembly in the tanks (6 1/2 gallon portable tanks) and it helped a lot, however, a marina told me they just aren't designed to run trimmed up that high like say trimmed up higher so you don't take your prop off in a gnarly area or loading the boat for the same reason so touching the choke might help like the other poster said... 

Thanks Chippman I will give that a try.

also try giving it some choke as you load it. that will give you an idea if it not getting enough gas If that works I'd start with replacing hose and bulb.

Check if primer bulb stays hard may have air leak.

Anyone have a similar experience or potential diagnosis?