90HP Merc Idles in water, not on muffs

[efdog]

I've got a 1997 90HP Mercury 2 stroke.Any posts I've seen all seem to be the other way around. Well I idle fine in water, but when I come home to flush, it runs for about 2 mins, then stalls. I'm thinking it must be a water pressure issue, but would that cause me to stall. It's peeing good right from the turn of the key, so I wouldnt think it's overheating. I can wait 10-15 mins and restart, but get the same thing. Dies in 2 minutes.
Anyone ever hear of this problem?

 

[efdog]

Re: 90HP Merc Idles in water, not on muffs

Nobody has heard of this before? Really I just want to make sure that I'm not doing any damage. Any reply is greatly appreciated.

 

[Barnacle_Bill]

Re: 90HP Merc Idles in water, not on muffs

Well it is certainly different. I'm wondering if you are turning the water pressure up too much. It shouldn't make a difference but it doesn't need to be turned up high.

 

[j_martin]

Re: 90HP Merc Idles in water, not on muffs

Well it is certainly different. I'm wondering if you are turning the water pressure up too much. It shouldn't make a difference but it doesn't need to be turned up high.

Water pressure doesn't make much difference, but water temp might. That coupled with slightly stale fuel, and it might lean out at idle. You might fuss with the idle mix adjustment. Just remember where it was so you can put it back if you don't make any change, or you get it to idle on the hose and not in the lake.

 

[milehighboater]

Re: 90HP Merc Idles in water, not on muffs

are you running on a slanted driveway or flat ground?

 

[bullet 101]

Re: 90HP Merc Idles in water, not on muffs

Its because when you use muffs the exhaust doesnt have any backpressure

 

[roncoop75]

Re: 90HP Merc Idles in water, not on muffs

Its because when you use muffs the exhaust doesnt have any backpressure

That would be the other way around wouldn't it? He's idling WITH the back pressure, won't idle WITHOUT the back pressure.

Usually it's the other way around.

 

[efdog]

Re: 90HP Merc Idles in water, not on muffs

Thanks for all of the replies.

roncoop75, yes that's correct. I'm idling great, never stalls on the water. No back pressure, and it stalls out in a couple minutes.

milehighboater, yes my driveway is slanted slightly. I'm tilting the motor all the way down to get it as eye level as possible, but I suppose it's probably still on a bit of an angle. Could this be my problem?

j_martin, fuel is good. Well water is ice cold, just like the Saint John river where she idles great. I dont want to mess with the mix adjustment in case this effects how I'm idling with back pressure...it does seem to be fuel related as it has the same effects as flooding when I try to restart, and similar to flooding will restart in 15 mins or so.

 

[j_martin]

Re: 90HP Merc Idles in water, not on muffs

It's probably idle fuel mix, that happens to be perfect with back pressure, and a little lean without. If it were a bit richer it might run in both circumstances, but you would probably be a bit rich on the water.

If it idles, and accelerates well, I'd just leave it alone and set the warm up lever up a bit while you're rinsing it out. If acceleration is a bit sluggish, it'd be worth the trouble to set the idle mix a bit richer. Probably would solve both problems.

Normal idle setup is quite rich to provide some of the fuel needed to get it wound up at the hole shot.

hope it helps
John

 

[jimg984]

Re: 90HP Merc Idles in water, not on muffs

exhaust fumes may figure into the problem

 

[bullet 101]

Re: 90HP Merc Idles in water, not on muffs

More than likely there is no problem at all. some outboards just wont idle without backpressure

 

[efdog]

Re: 90HP Merc Idles in water, not on muffs

J martin...thanks, I think I may need to richen up a bit, as it does stumble a bit upon acceleration, and can be a very rough idler, even for a 2 stroke. To make a very small adjustment, do you think 1/8 of a ccw is going to help? If so, should I turn all 3 scrrews?

Thanks for everyone's help!