1988 Mercury XR4 (150hp) - Idle Problem

[Glastron1987]

1988 XR4 (150 Black Max) starts great cold, runs great at nearly all speeds, slow, medium, and WOT. The problem is idle. Some times it idles fine, and sometime it gets into a funk where it is hard to start warm and likes to stall at moving idle. To start it, I can always over come this with the right combination of choking and lifting the high idle arm, but the moving idle frequently remains questionable and may still stall out. This is annoying for me, but it is my wife who is driving when I am skiing and it is impossible for her. If I set the idle up with an engine adjustment it seems to be fine, except at that point the idle is too high and is tough on the LU gears when shifting into gear. Timing advance/idle stabilizer has been disconnected, and sync and link has been done. Carbs and fuel pump have been rebuilt. Anti-siphon valve from the tank was removed. All of these things had no affect. Any clues? Do all these engines run bad like this? Do I have to upgrade to an EFI or Optimax? Thanks.

 

[jigmister]

Re: 1988 Mercury XR4 (150hp) - Idle Problem

The engine should idle without a problem. I had the same type of problem and turned out to be the idle jets. Take the brass plugs out of carbs and clean the jets. It dose not take much to cause an idle problem.
Also make sure those plugs are tight and gaskets are good. If the seal is not tight you will have and idle problem.
its possible there is a sticky float or a float adjustment it too high.

IT took me a few trips out to work out these bugs after I rebuilt the carbs. Once I got the bugs out it runs and idles really
nice
1986 175 hp black max

 

[Glastron1987]

Re: 1988 Mercury XR4 (150hp) - Idle Problem

When I had the carbs apart the floats looked perfect and the carbs were surprising clean. Re-cleaned anyway. Will recheck the jets and check for any leakes. Thanks.

 

[jigmister]

Re: 1988 Mercury XR4 (150hp) - Idle Problem

you can squeeze the fuel bulb while looking down the carb throats. Dripping fuel indicates improper float adjustment or some problem with the needle and seat.

 

[sunrunner classic 248]

Re: 1988 Mercury XR4 (150hp) - Idle Problem

Hi iwas hopeing u might be able tohelp my boat was running perfect but one day i was at full throttle and had to bring it back kinda fast and now it will not idle itjust stalls every other speed its fine

 

[Glastron1987]

Re: 1988 Mercury XR4 (150hp) - Idle Problem

Thanks for the tip on how to check the floats. That may be something I can check in the water, without pulling out the boat.