1986 Mercury Classic 50 problem

[Bigbassguy]

I just picked up an '86 Mercury Classic 50 - 45 hp 4 cyl last fall that runs great, but for some reason when I am making a long turn (like turning around to go the other direction) while on plane the motor will bog down and die. It only does it while turning. The first time it happened it started back up just fine but when I gave it throttle it was like it was starving for fuel and did not have any power for about 5 minutes. The strange thing about it was I was able to put the motor in nuetral and it revved just fine. After 5 minutes the motor just came back to life and I didn't have any issues the rest of the day.

The second and last time it did it last weekend I made a hard turn and after about 10 seconds into the turn I hear a loud pop from the motor so I quickly power down and then it sounded as if something had seized as its coming to rest. I took the hood off to see if I can see anything wrong with it but nothing, I tried to turn the motor over, the starter engages but can't turn the flywheel. I let it sit for 10 minutes and went to try and start it again, and this time the starter turns the flywheel but not nearly fast enough to turn over. I bring the boat home and hook up the muffs to it and it starts right up no problem.

I'm thinking something is overheating in the lower unit itself, but I have no idea where to look. The water pump is working properly and pee's just fine. The only thing I haven't checked yet is if it has water flowing through while on plane or making a turn, but I will try and do that tomorrow. Does anyone have any other thoughts on what this might be or where to look? I'm usually pretty good at this kind of stuff, but this one has me stumped, any help would be greatly appreciated.

Thanks in advance,
Rob

 

[8075mercury]

Re: 1986 Mercury Classic 50 problem

I would check and see if your tattle tale hose (or pee hose) is coming off the top or bottom of the block. Some of these years come off the bottom of the block (do not know why??), so you might be getting overheating on the top of the block and still getting pee water. I changed my pee hose to the top of the block by drilling and tapping a new hole. If this theory is true, the top of the block should be getting super hot also.

Good luck, these are super motors.

 

[Bigbassguy]

Re: 1986 Mercury Classic 50 problem

Its coming out the very top of the block. Thanks for the input though.

When I took the cover off the second time it happened I was able to touch the block with my hand, (this was after a 4-5 minute trip across the lake) it was hot but not so hot that I had to pull my hand away. The temperature seemed normal. Thats why I'm thinking it has something to do with the lower unit or bottom half of the motor itself. Is there supposed to be cooling water pumped through anywhere else on this motor besides the engine block that might be clogged?

 

[8075mercury]

Re: 1986 Mercury Classic 50 problem

Well that is good news that the water pee hose is off the top of the block.

I think I would extend the pee hose to where you can watch it in turns and see if you are losing water flow.

(The cooling water is pumped from the lower unit up the discharge tube to the bottom of the block and then out the discharge (and pee hose).)

 

[Bigbassguy]

Re: 1986 Mercury Classic 50 problem

Took the boat to the lake today to check the water flow while on plane and while turning and it comes out really well with a ton of pressure. So now I'm back to the beginning. It didn't stall out today while making any hard turns but it didn't seem like it was running at its optimum during those turns.

SO, if anybody has any other ideas about what could be going on I would greatly appreciate your feedback.

Thank you

 

[CharlieB]

Re: 1986 Mercury Classic 50 problem

At the dock or on the trailer look very close to the fuel line before the motor. You are looking for and tight bends or pulling on the hose while the motor is turned, you could be restricting the fuel supply and leaning out upper an cyl such that siezing occurs, the motor locks up until it cools, gradually you will lose compression in that hole until it becomes necessary to bore it and replace a piston.

If it has removable fuel tanks be aware of how you set the tank in place so that fuel line has adequate 'slack' to allow movement in turns.

 

[crem1]

Re: 1986 Mercury Classic 50 problem

Hi!

When is the last time you did a thorough carburator cleaning in a solvent and replaced the bowl and filter?

Alex

 

[Bigbassguy]

Re: 1986 Mercury Classic 50 problem

Thanks for the reply Charlie, that was something I hadn't thought of. But after looking and moving the motor to all extremes I don't believe that is the problem. I will take a look while on plane to see if the fuel line shifts into an awkward position though. At the moment there is plenty of slack in the line.

I will also take the plugs out and look if I can see any bad scoring or marking on the cylinder walls, hopefully thats not the case.

Thanks again!

 

[Bigbassguy]

Re: 1986 Mercury Classic 50 problem

Hi!

When is the last time you did a thorough carburator cleaning in a solvent and replaced the bowl and filter?

Alex

That was the next thing I was going to do, just haven't had time to do it. I ran some Seafoam in it this spring but I know that doesn't get everything.

The fuel filter was just changed this spring also.