merc 90 carbs

[bbarrons]

I need to rebuild my carbs on my merc (86) inline 6. they are wmk-39...... I have an oppertunity to get some wmk-40's from an inline 6 115 that were just rebuilt..... does anyone know if this is a compatible? can I make the switch?

 

[jimmbo]

Re: merc 90 carbs

They will fit but will not improve performance. They will in fact degrade accelleration.

 

[bbarrons]

Re: merc 90 carbs

Thanks for the reply. I am having a hard time finding a clean set of these carbs. I have one that the jet is all buggered up. someone tried to remove it to clean and it broke.
After logging into this forum yesterday and reading a ton of posts I find that my problems might not have been carbs after all but maybe a stator that was going bad. The motor has run fine for 6 years. strong compression in all 6 cyls (125 across all 6). It was running fine and then just stalled from a wide open run. It was hard to start and then would not go over 2000 rpm. We cleaned and checked the fuel system, changed plugs and checked spark on ea cyl.
am I on the right track????
the motor is a 1986 merc 90. The only problem in 6 years of ownership is 1 switch box.......
any thoughts??

 

[gungalunge]

Re: merc 90 carbs

I am not sure but I was experiencing that same symptom . if this helps i had a pump bulb the thing on your fuel line you use to pump fuel to the engine . well it came apart inside the rubber peice restricted the fuel line. I took the fuel line apart upstream pumped the bulb and gas blew off in my face and the restriction shot off some where . i replaced the whole fuel line hand squeese bulb and all my rpms are back and and no more hard starting also a nice new fuel filter on there now what a difference WOW

 

[gungalunge]

Re: merc 90 carbs

also you can get those carb jets on line if you look around. always be sure the jets seal off when screwed down an air leak there makes a difference ..

 

[bbarrons]

Re: merc 90 carbs

I was able to find the jets as part of a carb kit but the jet is broken off in the base of the carb. I cant see anyway to get it out. That is why I asked about the wmk-40's... i found a set that had been rebuilt and wanted to use them but if I am going to have reduced performance it isnt worth it. When this motor was running good it would push my 18.5 starcraft about 45-48 mph on open water. I had put a new fuel filter on and watched the fuel flow. the filter never really emptied.... pretty much stayed 3/4 full..... priming the bulb didnt make much of a difference either. I did find a wire coming from the stator that had been cracked and had exposed wires. I pulled the flywheel and inspected the stator but didnt know how to test it. I just made sure all wires looked good. There is a thread on this forum that expalins how to test it. Ithink I will dive into that tomorrow.

 

[bbarrons]

Re: merc 90 carbs

Okay, I pulled the stator and tested it. ohms are no where close. The white ( or yellow) wires are all cracked and corroded. I also tested the trigger and the ohms should be between 11-14 and I get 18..... can anyone tell me if that should also be replaced?
thanks for all the help so far......
Bill