I bought a boat with this 98 Merc 150 on it last July. Been a trial since. I didn't even make it from my friend's marina to my slip 3 miles away before the water pump impeller came undone and it overheated big time.
Long story short I replaced two regulators, both sending units, the valve on the head and bought a service manual. Oh and I had hit and miss oiling, after the gear on the crank lost some teeth. I replaced the oil pump assembly with the electronic version and it has worked happily since.
The engine has decent compression considering what it's been through. 100psi across the board. That was checked before winterizing it last fall. It will start right up cold and hold a nice idle. It will idle in gear after leaving the slip, no problem.
It will get up on plane with no balks.
Now if we go somewhere. like fishing, and we have to shut the motor down the problem begins. It will start and the idle will slowly drop until it quits. Sometimes it will idle fine, but the process is pretty predictable. Once you clear the hurdle of getting it in gear before it quits you can get the throttle up and be on your way. It's a PITA and embarrassing when you have to treat it like a jalopy to get it going.
Now I do notice my Tach drifts up with no increase in motor speed every once in a while and I do notice that my volt meter drops from 14v to just above 12v sometimes in tandem with the speed of the motor and sometimes without. It will also rise to from 12v to 14v.
I have yet to see it holding at 14v when the motor quits. If it's humming along at 14v it will stay rock solid. I don't know if this is a case of the tail wagging the dog or vice versa.
In any case I will be building my DVA to test the stator and switchboxes in the next coming days, but in the meantime I would like to hear anyone's experience with these symptoms. My gut tells me stator and I say that because from what I have read they are problematic and couple that with overheating and there's your problem. But I am not going to rush right out and plunk down $400 for a new one until I diagnose what's going on.
I could also bother my friend who services Mercs, but they are busy, I value our friendship, and I would like to accomplish this myself. He also likes to say "buy a new motor"
Not gonna throw parts at it, promise, just want to own what I have. I need to fix it. I don't like when things don't work.
Thanks
Scott
Long story short I replaced two regulators, both sending units, the valve on the head and bought a service manual. Oh and I had hit and miss oiling, after the gear on the crank lost some teeth. I replaced the oil pump assembly with the electronic version and it has worked happily since.
The engine has decent compression considering what it's been through. 100psi across the board. That was checked before winterizing it last fall. It will start right up cold and hold a nice idle. It will idle in gear after leaving the slip, no problem.
It will get up on plane with no balks.
Now if we go somewhere. like fishing, and we have to shut the motor down the problem begins. It will start and the idle will slowly drop until it quits. Sometimes it will idle fine, but the process is pretty predictable. Once you clear the hurdle of getting it in gear before it quits you can get the throttle up and be on your way. It's a PITA and embarrassing when you have to treat it like a jalopy to get it going.
Now I do notice my Tach drifts up with no increase in motor speed every once in a while and I do notice that my volt meter drops from 14v to just above 12v sometimes in tandem with the speed of the motor and sometimes without. It will also rise to from 12v to 14v.
I have yet to see it holding at 14v when the motor quits. If it's humming along at 14v it will stay rock solid. I don't know if this is a case of the tail wagging the dog or vice versa.
In any case I will be building my DVA to test the stator and switchboxes in the next coming days, but in the meantime I would like to hear anyone's experience with these symptoms. My gut tells me stator and I say that because from what I have read they are problematic and couple that with overheating and there's your problem. But I am not going to rush right out and plunk down $400 for a new one until I diagnose what's going on.
I could also bother my friend who services Mercs, but they are busy, I value our friendship, and I would like to accomplish this myself. He also likes to say "buy a new motor"
Not gonna throw parts at it, promise, just want to own what I have. I need to fix it. I don't like when things don't work.
Thanks
Scott