1990 Mercury 150 XR4 idle problem

[threeboysgolf]

I've had this used motor for one season. The last three trips out, it's been hard to start and then keep idling. Once I get it started, I have to put in gear quickly and go to full throttle. It runs fine at WOT and pushes the boat at 63mph on GPS. Called the local Mercury dealer and they said it could problems with the stator. Is this possible?

 

[Jacket4life]

Re: 1990 Mercury 150 XR4 idle problem

I've had this used motor for one season. The last three trips out, it's been hard to start and then keep idling. Once I get it started, I have to put in gear quickly and go to full throttle. It runs fine at WOT and pushes the boat at 63mph on GPS. Called the local Mercury dealer and they said it could problems with the stator. Is this possible?

I'm no expert at all, but this was the exact same issue we had with our Merc 40 and we replaced the plugs and it immediately cleared up. Been told by a lot of ppl smarter than me that plugs are a cheap and easy fix for a lot of what ppl call "problems" with any internal combustion engine. After reading around here, I'd make sure you check and get the correct plugs for your engine.

 

[j_martin]

Re: 1990 Mercury 150 XR4 idle problem

I'm no expert at all, but this was the exact same issue we had with our Merc 40 and we replaced the plugs and it immediately cleared up. Been told by a lot of ppl smarter than me that plugs are a cheap and easy fix for a lot of what ppl call "problems" with any internal combustion engine. After reading around here, I'd make sure you check and get the correct plugs for your engine.

It would be well worth your while to get a factory manual, and do a formal tune-up on it. If it hasn't been checked out in awhile, I'd put in plugs, check all the bleed check valves and lines, look over all the fuel system lines, do a little squeeze the bulb test for carburetor flooding, throw in a fuel pump kit, and then do a link n sync.

If the idle timing doesn't set up somewhere near the book, then tear into the carbs and clean and adjust them.

That engine is worth a little tender loving care, and it will pull like crazy if you take care of it. Let it lean out because of a dirty carb or weak fuel pump, and it'll grenade and throw rod caps at you.

hope it helps
John

 

[4Bassin]

Re: 1990 Mercury 150 XR4 idle problem

I had an 89 XR4 with similar issues. I replaced the reeds and it improved it immensely. It ran fine but the floats were real sensitive and I realized it would idle rough if the motor was trimmed up or down too far. It would run fine with a level trimi but much off center and it would act up. I could not believe the difference new reeds made though.

 

[j_martin]

Re: 1990 Mercury 150 XR4 idle problem

I had an 89 XR4 with similar issues. I replaced the reeds and it improved it immensely. It ran fine but the floats were real sensitive and I realized it would idle rough if the motor was trimmed up or down too far. It would run fine with a level trimi but much off center and it would act up. I could not believe the difference new reeds made though.

If the other tune items are in reasonable shape, then reeds are next. If you take the carbs off, it's only one more gasket to take the reed plate off so you can inspect the reeds.

hope it helps
John