Mercury 8HP 1988

davidpbo

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Boatless in Cheshire. Formerly 23ft Jeanneau Tonic
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Servicing my Mercury 8HP 2 Stroke I took the prop off to run it in a tank without realising there were bits behind it that might and did fall off. I didn't realise until I put the prop back on and engine made unusual noise when in gear. I fished around and retrieved the bits but as they don't match the diagram in the manual I would appreciate some input.

One of the bits was splined inside and fits on the prop shaft on the gearbox side of the propeller, it has three teeth on the outside which appear to mate with three notches on the fixed part of the casing, should they and if so why? Or are they meant to create some turbulence maybe to do with the exhaust? The other part was a metal ring with a shoulder that appeared to fit on the outside of the first bit.

I have installed these with what I can only describe as the nut of the splined part towards the gear box and the other part cupped over the three teeth, then propeller, splined nut and lock nut.

Anyone know if this is correct. Are there any other bits I should look for?

How do these engines get air into the casing? I set mine up ok with the cover off, put it on and it loads up as though short of air, I can find one hole 1/4" dia near the water outlet and a gap near the leg.

| am also having a job getting it running right anyway. Timing checked but when I throttle back having been running fast for a while it often cuts out. Any ideas ??

Too rich a mixture? Too lean?

Idle is set about right, too fast if anything

I think I probably need to start from scratch when I not knackered from repeatedly starting the engine.
 

davidpbo

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I was servicing and checking it.

Replacing w.pump impeller, checking timing and mixture etc.

By and large the engine was starting and running OK but has always had a problem when throttled back quickly from medium/high revs to idle quickly which is what happens when manouvering the boat. It often stalled unless the idle speed was set quite high using the external knob.
 

Kawasaki

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Checking timing and mixture etc.
How did you check the timing and have you altered it?
Mixture?
Not much to alter there I don,t think.
If you have to screw the tickover "knob" in a bit to overcome a stalling idle prob, summats up.
Make sure there is some "free play" in the throttle cable.
Let her tickover and pull the outer cable where it sits on top of the carb.
There should be some "slack" , just a bit, ie you should be able to jiggle the outer cable without the engine wanting to "rev up" if you get My drift.
Also to make sure the cable is not too "tight".
Whilst She is ticking over, move the tiller around from one extremity to the other.
Sometimes if the cable is not set right you will notice an increase in revs when You do this.
Will the engine tickover reliably when warm, ie at working temperature for a while?
Sorry to throw more questions at You.
Tiss difficult diagnosing from a distance!
K
 
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