1985 150 Merc. runs poorly until warm and overheats

[SparkieBoat]

My friend has a 1985ish 150 Merc. I have not run the serial numbers yet but I think year is about right. I do not have much experience with mercs..mostly been working on OMCs. His motor runs poorly and overheats until motor has been run for a little while..after motor has been run for a little while (10-15 mins) it just starts running great and does not overheat, and will continue to run fine until motor gets cold and then it starts all over again...I suspect that the motor has some type of timing cold start feature that is not working properly. I assume that timing is being advanced and not released as it should when rpms and temp reach certain levels..What component(s) controls this feature and how do I test it.

 

[j_martin]

Re: 1985 150 Merc. runs poorly until warm and overheats

Actually, that motor is almost as dumb as a pickle. The only timing advance on it other than mechanical with the throttle lever is an idle stabilizer or advance module that slightly advances the timing at very high rpms, then retards it when you really need it. Best place for that module is the chit can.

I guess it is possible for it to cause trouble in the way you describe. To test just disconnect it from the switchboxes. If it runs better, do a link n sync on the motor and substitute 23 degrees for the WOT timing spec.

I suspect, however, that the primary problem is a stiff as a board, 6 year old water pump impeller.

hope it helps
john

 

[SparkieBoat]

Re: 1985 150 Merc. runs poorly until warm and overheats

thanks John, I will do what you suggested. I am also going to change out impeller and t-stats and gear oil. it runs poorly when you first crank it up..it bogs out and will run hot..I suspected a timing problem because of it running poorly, then just like you flipped a switch after about 10 mins, it runs perfectly with no overheat. By the way ..I really love pickle stupid motors, less stuff to go wrong.......ROFL...I wish they could still make them, my friend has gotten great use out of his, with very little maintenance.

 

[j_martin]

Re: 1985 150 Merc. runs poorly until warm and overheats

thanks John, I will do what you suggested. I am also going to change out impeller and t-stats and gear oil. it runs poorly when you first crank it up..it bogs out and will run hot..I suspected a timing problem because of it running poorly, then just like you flipped a switch after about 10 mins, it runs perfectly with no overheat. By the way ..I really love pickle stupid motors, less stuff to go wrong.......ROFL...I wish they could still make them, my friend has gotten great use out of his, with very little maintenance.

If it has good compression, and you get the maintenance manual and get serious about testing out all faults and properly adjusting everything, you'll have one of the strongest, most reliable motors on the water.

It doesn't take much money, just a lot of putsy work.

hope it helps
john

 

[SparkieBoat]

Re: 1985 150 Merc. runs poorly until warm and overheats

it is a very strong motor for sure..it is on a 18' very wide Ranger and will bust 55 mph wide open..I have a 1996 60 degree GL model rude with optical ignition and it seems kinda weak compared to this motor. after close inspection the red wire coming from module was frayed and almost severed. after disconnecting both wires, motor is now running out nice...still wanting to overheat... a new impeller is on the way. Is there any way to set WOT timing besides running down the river???

 

[j_martin]

Re: 1985 150 Merc. runs poorly until warm and overheats

it is a very strong motor for sure..it is on a 18' very wide Ranger and will bust 55 mph wide open..I have a 1996 60 degree GL model rude with optical ignition and it seems kinda weak compared to this motor. after close inspection the red wire coming from module was frayed and almost severed. after disconnecting both wires, motor is now running out nice...still wanting to overheat... a new impeller is on the way. Is there any way to set WOT timing besides running down the river???

Wot timing is set while cranking the engine.

Get the book and do a formal linkage and timing adjustment on it. There's several inter related adjustments, and a proper order to do them. When you get to WOT timing, it'll call for 19 degrees. Use 23 instead without the module.

Do it right. That engine is good for about 160 or 165 HP at the prop if it's in good tune and adjustment. It'll grenade and throw parts at you if it's timed too fast or the mix is too lean.

I have an XR4 on a 18' Tracker and it does 60 with a fishing load.

hope it helps
John