mercury 850 thunderbolt timing problem

I have a 850 thunderbolt merc when in neutral it runs smooth and throttles up fine, but when you put it in gear in the water and the engine has to push the boat it doesnt have any power, it only acts this way when there is strain on the motor . It idles like new and will rev up in neutral and doesnt have any problems until it has to push the weight of the boat. A guy told me that it has to be adjusted on its timing, but I dont know how to move the distributor properly becouse the distributor advances with the trottle has it revs up. someone else said it may be points, but does this engine have points, and if so would this cause the problem. thanks I hope someone can help
Cory

Re: mercury 850 thunderbolt timing problem

Cory, You might post the serial number of the motor. We can then tell what kind of ignition system is has.

I recommend you start with the basics. Do a compression test. All the four cylinders( older motors have 6 cylinders) should be 100+PSI and even. If that passes put a timing light on each plug wire and run the motor. See if it has spark to all four(or six). Make sure the plug wires are not arcing to ground. If these tests pass it is likely your carbs are out of adjustment or dirty. Report back on status

Re: mercury 850 thunderbolt timing problem

I have almost the exact same problem my boat will idle and rev up just fine with the muffs on, but when i took it to the river it starts in the water and then as soon as i take off it dies out and will not start. and it seemed like everytime i gave the primerbulb a little squeeze the engine would start up again??? confusing to me hahaha. could this be the fuel pump or fuel filter?? I was reading a thread earlier that was talking about the fuel pump being right where the fuel line plugs in at on the engine, is this true? I found a rebuild kit on maxrules.com for the fuel pump?? but in the kit i dont see any kind of motor? is there not a motor that pumps the fuel??? and where can i find the fuel filter to possibly clean it out or replace it??