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1980's 9.8hp low on power

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RichardInDorset

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I have recently got hold of a 1980's 9.8hp, in very nice condition. It starts fine, runs fine but out on the water it will only make about 5-8knots on my 3.6m inflatable - it actually performs slightly worse than my 2.5hp 4 stroke!

It looks like it has never been dismantled as the bolts on the engine block are all still painted.

One thing I did notice was that the air intake guard is missing from the carb. When you prime the fuel, if you squeeze the primer bulb hard, fuel comes out of a hole near the intake guard mounting bolt holes.

On the parts diagrams this hole appears to have a plug (part number 16), so might this be a cause of low power?

I'm not sure if the plug is missing or if it is there and the fuel is leaking past it...

There's no fuel leak when running.

The throttle opens fully. The plugs are new.

I will check crankcase compression and take a look under the cover over the reeds/ports.

Anything else to check before I go further and start stripping it down?
 
So I got a CDI electronics coil, part 184-0001 and although the list of coils it replaces doesn't show the orange merc coil 339-5288, it is the same size and the coil measures the same resistance.

However, there is an earth wire on the old coil that goes to the motor case and on the CDI there is a metal strap that goes between the neg of the LT coil and the coil core.

Have I got totally the wrong coil or do I just modify it?
 
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They work the same. (I have one of each running on my engine at the moment.) Bolt her on and see what happens.

Jeff
 
NO! I meant to say that I have two different type coils of the same color (blue). The blue and black are interchangeable, as are the red, orange, yellow and green group, but these two groups are NOT with each other.

Jeff
 
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