[Edison]

I'v tried a few repairs and checks like going through the carburator changing needle and seat, floats were good, clean and reinstalled carburators.
I adjusted the idle screws and had the motor running just like it should in neutral. After launching in the water an trying to idle at slow speeds two-five mph. I had to reajust the idle screws to keep it running. Ran fine at speeds 5-55 mph. but after killing the engine i had trouble starting again and the problem i had before with the engine not being able to idle at slow speeds continues and it also continues to run fine at higher rpms. what do you think the problem may be?

[bhile]

Have you done a link & sync according to your manual?

[Chris1956]

Ed, The carb adjustment still may be a bit lean. You might open the carb mixture screw 1/8 turn and see if that helps your restart idle issue.

[Fenwick2]

I just read somewhere about someone who can make a 90 hp Mercury idle smooth as glass. If I find him I'll share that information ASAP. That's most likely a overstatement. That being said a Mercury 90 hp motor is the hardest starting, roughest running, longest lasting most dependable motor ever built. I would search for a good or great carb mechanic that has the tools to set those carbs to speck. You don't want to run lean and burn a piston. Or you could buy three new rebuilt crabs and install yourself or have installed. Carb tuning is a art form I.M.H.O. Or you could just ignore my post and keep trying to set them up yourself. I wish you a happy ending what ever you decide to do.

[j_martin]

I disagree with fenwick. Carb tuning is a matter of being thorough and careful. If they're clean, straight, adjusted to the book, and put together carefully, including watching torque patterns, they will be good.

Art implies freedom. The secret is just the opposite, it's constraint to the specifications.

How about the basics. Have you run a compression check on the engine. If compression is poor, I don't care how perfect your carbs are, it's gonna idle like chit.

hope it helps
John

[Fenwick2]

"I disagree with fenwick." That's a good thing. It's called brain storming and that's how problems are solved. We can all learn from eack other here. When one disagrees for good reasons it's up to us to either learn from it or be closed minded. I chose to learn from other peoples expertise on this site. You may have or do have more expertise then me in the carb tuning area and forgive me but I was wrong from the get go as I was referring to the 3 cylinder 90 h.p. Mercury not the 6 cylinder in my first post. My bad. Now is the problem close to being solved? That is what this board is about I.M.H.O.. Best Wishes.

[Edison]

thanks for all the replys.I checked the choke to see if it was stuck by disconnecting the outlet hose watching for fule as I tryed to start the engine wile holding the chok in an got a good flow of fule .Then I reajusting the idler screws on the carbs and now I have the engine starting alot easyer the thing is I also had it runing at a slow idle speed I took off went to the camp an when I got back to the launch I got the same problem again killing at low idle speed. any ideas?

[hkeiner]

I've tried a few repairs and checks like going through the carburator changing needle and seat, floats were good, clean and reinstalled carburators.

It is not clear if you cleaned the carbs by soaking them in carb cleaner and blowing out all passages with air. If not, the carb's idle speed jets and related passage ways may be gummed up. A carb's internals can look clean visually but still be gummed up. I believe that it is best to soak carbs in carb cleaner and then blast all the passages with air to be sure that the carbs are clean.

[Chris1956]

For the record, I never was able to adjust the idle mixture on my inline six, following the "destructions" in the OEM Service manual. I had pretty good luck with the following procedure however.

Set idle needles open 1-1/2 turn from lightly seated. Start and warm motor in the water. it will be best to start adjusting the idle mixture while running in gear, but I have done it in neutral as well. Slowly turn the needles in, starting on bottom carb, until max idle speed is achieved. Sometimes you need to turn them out a bit as well to maximum idle speed and smoothness. Now try to accelerate. The motor should either die or stumble. Now open the idle mixture on the top carb 1/8 turn and try to accelerate. it should accelerate a bit better. Open the idle mixture on the mid carb 1/8 turn and try to accelerate. it should be better yet. Next is the lower carb. Continue until you get decent acceleration and a reasonable idle. Start again at the top carb. Generally on the inline motors the carbs on the bottom run richer than the top carbs. So don't richen the bottom carb very much, it usually doesn't need it.

[Edison]

I dont know whats going on with this engine . I get it running good at slow idle speed like I need it .I can take it out of gear and it will idle just fine so I took it for a run slowed back down ideled just fine .So I gave it another try idleing down the canal taking it in and out of gear run just fine .I thought I had the problem solved but after running back to the dock and trying to go back to an idle agian the engine started stalling whats going on????????

[daveswaves]

It may have "eaten" a couple of bleed restrictors. The only way to find out is to remove the transfer ports and look. There should be 5, the bottom cyl does not have one.
I cannot overstress link and sync, search this site for Clams Cannios post on it, that will put you on track.
Also timing, 21 degrees max, forget what it says on the sticker.
Check your throttle/shift cables, if they are loose the carbs wont return to the same setting each time.