1986 60 hp 2 stroke mercury idle bad

3 cylinder. Melted the electrode of a loose spark plug last week. I pulled the exhaust port and looked, damage not bad in cylinder or piston. Harbor freight compression meter reads 80 lbs on all cylinders with motor cold, all plugs out, throttle at start position. Several checks. Took the boat out yesterday. To start engine, I choke it and hit the starter till it fires(approx 5 - 7 revolutions), throttle at idle/start position. Will not start with choke(enrichment) on. Take choke off and hit starter, cranks it 2-5 revolutions. Runs great at WOT or any speed above idle. When it has been sitting for a day it will crank and idle after start, shift, back away from dock, ease 1/4 mile through no-wake area, all really well. Comes to speed and get to fishing hole, park and shut down.
This is the problem: When I start it after the above, it will die unless I slam the throttle open fast. Starting procedure is the same as cold start unless I have just shut it down moments before; give it 15 minutes and if I do not snatch it wide open it dies. Occasionally it fails and dies after I snatch it wide open, doesn't seem to catch up. If I get 5 seconds of run it will continue, will idle fine. Idle speed adjust screws: In the water, warmed up, tighten till it staggers. Then loosen till it staggers. Then get 1/2 way between those two settings, then loosen 1/4 turn. Any ideas? Help! Immediately after I shut down, it will start right back up with no choke and run fine.

IF--repeat--IF this is the two carb, earlier triple, the below is applicable"

These are tough motor to adjust idle on! I run these and found that the ONLY way I can get the darn things to idle is to use an infrared temp gage. to Wit:

Warm the motor thoroughly. Aim the red dot at the base of each plug and note the readings--should be around 85 to 100 ' F. Adjust the idle mixture screws to get all three plugs the same temperature. Finally, add 1/4 turn OUT on the idle mixture screws.

Jeff

PS: If you haven't done this yet, remove the water line going to the fuel pump (from the exhaust adapter plate below the motor) and plug it. These motors have an undersized impeller and need all the cooling water going to the power head. Trust me on this!

Thanks Jeff! I have an infrared temp gauge, I will do that. Bad weather forecast today, Gordon coming to visit, so might be a couple days.
On number 2 - I had no idea there was a water line to the fuel pump. I rebuilt the fuel pump and thought I found: 1 line = Fuel In. 1 line = Fuel out. 1 line = pressure/vacuum from the crankcase. And that was it. I will go out and check right now, that would answer several questions.

Oh, yes it is the two carb model. It has mucho cooling water running though it, I am paranoid about cooling and keep a new impeller in it, I have a new impeller sitting in the bag ready to install. It puts out a solid 3/8 stream from the top outlet pee hole that runs just pretty warm, way less than boiling to my hand.

Don't you think that is low compression for this motor? If lower compression when this animal is colder, try a warm compression test. My 115 stays about the same hot or cold, but only 80 psi on mine too. I consider this a "sick" motor. It is not acceptable to me for performance, or economy. Do you have another gauge to borrow? I will never schedule an overhaul unless I have really made sure.

Hey Tim - I agree it is low compression. Problem is that the motor runs great. I use it on a pontoon boat, and spent six hours out with it day before yesterday. The only problem is using the motor at idle. If I can cure that by adjusting the carbs per jeffs suggestion, then even if it does have low compression I will be happy to use it till it fails. When I bought the motor the guy who sold it told me it had 130 compression. I checked when I got home and got 100 across the board. Figured it was crappy compression tester, but called him and he swore it was 130 and the rings were probably stuck. I don't want to buy another tester, I think the harbor freight set I have is just reading low. If I can figure a way to test it with my air compressor that would be good. I will let you all know. Thanks for the posts! I really appreciate having someone else look at this stuff and give me ideas.

One of the symptoms of lower compression is a poor idle and it often gets worse, try adjusting and hope for the best, right?

Dan I cannot tell from your posts where you live. But in another month or so, I will be putting my pontoon to bed for the winter.

I have found that if I fog my cylinders with Seafoam Deep Creep it will loosen up the rings devolving the carbon build up and improve the compression while my boat is winter storage.

I am sure that if you contact the Seafoam people they will tell you it will work faster than over the winter, but I do it as part of my winter maintenance.

It is just a thought.

Great advice. I have always stored with 2 stroke petrol base oil in cyl. The Amsoil I use is not quite as good for rust dissolving or stuck rings.

I'm in LA (Lower Alabama, you prolly noticed my lack of accent). I intend to keep this boat on the water unless it freezes, and when it freezes here hell is probably chilly too. I love seafoam. I get a can every now and then and add it to a 6 gallon tank of gas and use that gas up on the water. When I had the exhaust ports off last week, I filled the cylinders up with seafoam and let them soak. I was working getting a broken bolt out so I had a can of pb blaster handy, when it wasn't full of seafoam I sprayed pb blaster on the rings and in the cylinder and worked them. Top cylinder ring 1 (nearest the spark plug) is free, the other two had very little or no movement when carefully pressed with the tip of a screwdriver. All other rings are free. After I got the bolt out and put it together I ran it 5 or six hours off and on, fishing. WOT is excellent. Stripped out my antique control handle, just finished today putting a new binnacle mount control on for shift and throttle. Cranked the motor and left it idleing while I lit the grill for the wife - stuffed jalapenos wrapped in bacon, steaks and potatoes, brocoli w/cheese on the side. I already had the heart attack, guess she wants the insurance money....anyway, I checked the plugs with the infrared. On the metal part of the plug the wrench fits, top to bottom, i got 124, 123, 134. I loosed the bottom carb idle screw till I got 130 bottom, worked on top and middle till all are 130 degrees plus or minus 1 degree. I shut down and waited 10 minutes with the water running, then hit the key. It started in about 1/2 revolution. I let it set 20 minutes, same. I got to get it on the water to tell for sure, but so far I am pretty happy. Thanks Jeff - I would never have thought of this. Appreciate all you guys input.

Hey Tim - I am pretty close to getting a set of rings and gaskets for this thing. I will find someone to clean out the cylinders and see what rings I need, bore the head if it needs it, and put the new rings in. Unless some of you guys tell me that would be a bad thing.....I have rebuilt auto engines before in my mispent youth, never did a boat motor before. Might be able to hone the cylinders, replace the rings, and be off an running. Would be nice to have ring compressor, these have to go back in from the back.