75 HP Mercury Outboard - 1989 - Coils bad?

[spike212993]

Serial Number: OC265997......I have been having trouble with my motor stalling when I open the throttle past approximately 1/2. It will run for about 30 seconds and then shut right down! We have cleaned all 3 carbs. I have sprayed water on plug wires and coils and saw no arcing (but I was only in shade, not night time). I pulled the plug wires off while idling, and although there is spark to all three, there was little change in the way the motor ran when I removed the bottom plug wire. I have ordered fuel pump diaphragm kit as well as coils. By the way, i replaced the spark plugs, and all three looked the same when I did. New gas with stabilizer as well as seafoam first 6 gallons, and gas with stabilizer thereafter. Any thoughts or suggestions would be appreciated, and thanks in advance. Jamie.

 

[Barnacle_Bill]

Re: 75 HP Mercury Outboard - 1989 - Coils bad?

Fuel pump kit should fix your problem. Be sure to replace the check valves when you do it.

 

[James R]

Re: 75 HP Mercury Outboard - 1989 - Coils bad?

If there is no change when you pulled the bottom plug wire, the bottom cylinder is not running. Have you done a compression check. You need fuel, compression, and a spark at the correct time to have a running cylinder.

 

[spike212993]

Re: 75 HP Mercury Outboard - 1989 - Coils bad?

Yes, compression was good. Thank you both. I guess I'm at waiting for the parts and trying them. I believe the diaphragm kit comes with the check valves. I will check. Thanks again. Jamie...Lance Corporal - USMC former.

 

[spike212993]

Re: 75 HP Mercury Outboard - 1989 - Coils bad?

UPDATE: Now, we have discovered that gas is getting into the oil resivoir, probably a bad check valve withing the fuel pump. Rebuild kit has been ordered, as well as one replacement coil assembly. Wish me luck

 

[spike212993]

Re: 75 HP Mercury Outboard - 1989 - Coils bad? UPDATE

Re: 75 HP Mercury Outboard - 1989 - Coils bad? UPDATE

I have rebuilt the fuel pump and replaced 2 of 3 coils. When I tested it at the launching area, it started hard, and once started, it would not accept increased throttle without dying. Also, I did not see any smoke at any point. NOTE: I did replace the oil in the injector resivoir after parts mentioned were replaced...Any thoughts would be appreciated. Thanks in advance.

 

[spike212993]

Re: 75 HP Mercury Outboard - 1989 - Coils bad?

UPDATE AGAIN: Well, with the new coils and a carb adjustment, we tested it on the pond. We found it still would not run right, and there was steam, not smoke coming from the exhaust. We are now replacing the head gasket (under the cover where the spark plugs are). Waiting on parts. I will replace the thermostat as well as long as we are in there. I will update later.It appears that the only way water could be getting into the cylinder is by sucking it in through the spark plug threads! Hmmmm.........Perhaps in being careful to NOT overtighten, I am not getting them tight enough, OR, the gasket was not sealing in that area. There was no 'stick-em' on the gasket around the spark plug area of the gasket. Any thoughts would be appreciated.

 

[spike212993]

Re: 75 HP Mercury Outboard - 1989 - Coils bad? UPDATE

Re: 75 HP Mercury Outboard - 1989 - Coils bad? UPDATE

I have blown the motor. Apparently I ruined the motor BEFORE I rebuilt the fuel pump. The fuel/oil mix was not happening properly, and I have ruined the bottom cylinder as there is 0 compression, and only 90 on top and middle cylinders. If anyone would like to buy the motor to rebuild, drop me a line with an offer. The motor is housed in Lewis, NY. The good news is, I pick up a new boat package on Monday!!!!!!!!!!!!!!!!!!

 

[tydog]

Re: 75 HP Mercury Outboard - 1989 - Coils bad? UPDATE

Re: 75 HP Mercury Outboard - 1989 - Coils bad? UPDATE

hi if you still have the mariner 75hp for sale please e mail me krouset@hotmail.com or leave me you phone number im interested. tyler