Why are Mercury 9.9s so cold-blooded?

[ET]

I have two friends with four stroke 9.9hp Mercury kickers. One is a 2000 and the other is 2002. They run the exact same. On start up they need to run for several minutes before they can be put in gear to take off. If you are in cold water it takes longer and if you shut the darn thing off for a few minutes, it is just like starting cold again.

I've had several people explain it as, "It's just their nature."

I don't buy it. There must be a higher temp thermostat or something that would help.

Anyone have any constructive ideas? (I love my Yamaha..so don't go there!)

[fishingls]

In 1987 I purchased my first 4 stroke Yamaha kicker. It was a 9.9 high thrust with electric start. It was a very cold blooded motor. I understand that the power heads used by Mercury are a direct kin to the Yamaha (I might be wrong but this is what I have read and have been told). My 9.9 had an automatic choke that never seemed to co-operate. I never found a solution to the cold nature of my 9.9 Yamaha until the 8 HP Yamaha came on the scene.

[Boat Doc']

The reason why they are cold blooded is they have to run lean to meet emissions standards. What the manufactures do is they take a carburater off the assembly line and flow test it and adjust it to preset values. They then apply those same adjustments to a batch. So there is room for fluctuation which can cause some to be to lean resulting in what you are seeing. If you access the idle mixture screw and richen it up you will eliminate the issue. This could apply to all engines not just Mercury.

[ET]

Thanks Boat Doc! Now that's an answer that makes sense! We'll give it a try.

[Orca]

I see no adjustable idle mixture screw on these small Merc carbs. Believe you will have to change jets.

[Starfish]

I see no adjustable idle mixture screw on these small Merc carbs. Believe you will have to change jets.



It should be there, just hidden behind a brass plug that can be removed and discarded.

[IDWITHELD]

Um, doesn't run lean = more heat???

[Starfish]

Only if it'll stay "lit". Cold engines want a rich mixture (e.g. choke). Once it's up to full temperature, lean engines run great (and, as you pointed out, run hotter).

[fishncliff]

Maybe that will help my Mariner 50hp. It hates to start. I have to shoot it with starter fluid.

[Streetwalker]

I had the same trouble w/the 9.9 I used to have. pulled the brass plugto access the mixture screw & fattened up the mixture quite a bit. It ran great & started easy after that.

[MacEFL]

I think that mine was drilled out. Now I can kick it in gear immediately!

[IDWITHELD]

My honda 9.9 is a dog to start first thing in the morning.

Choke choke choke thud. RRRRRR-RRRRRRRRR-RRRRRRRRR choke choke choke put-put=putttttttt rum rum ruuuuummmmmm. Idles good after 5 minutes.