Do you Need to Use The Force on The Dark Side!!??

[chris-p]

Agreed to work on a couple Mercs. Now regretting it, lol.

They are the blue stripe (70s, 80s?) 9.8hp and a 4.5hp.

The 9.8 was easy enough. Strange water pump though, from what Im used to. Seems like getting the new impeller in will require some trickery. Hose clamp or??

The 4.5hp seems like a silly design. How do you test compression and spark, without drilling a hole into the cowl? Probably a stupid question, but have to ask. Not even a notch on the flywheel to use a rope on.

[dave-bernard]

impeller use a tie wrap or pvc pipe. compression install the gauge put the tpo back on crank it over remove the top and read the gauge. spark takr plug out ground plug and flick the flywheel with your hand. no problem.

[legendre]

Make sure the 45 has the correct surface-gap plug installed.

BTW – they are actually 5hp, not 4.5 as you’d think.

[chris-p]

If I remember right, the gearcase and motor need to be in fwd when you reinstall gearcase, or is it neutral?

[benchrascal]

Those motors are some of the easiest to service and well designed ever made.They can be a little daunting to begin with but after going through the paces they’re pretty straight forward (with the possible exception of prop removal which is just a complete disaster) I just rotate the impeller and press down onto the key with either of those .To test spark and compression with the cowl off I just use a rechargeable drill fitted with a socket after screwing in my gauge and attaching my shop built spark tester .Just did one of mine this evening ,whole operation took about ten minutes .

[billw]

You actually have to use LESS force on the dark side. Mercurys do not tolerate hammer mechanics as well as OMCs do. Be patient and think, before doing anything.

I, too, just spin the impellers in by hand. No big deal as long as the shaft is not rusty. As for compression, Mercury made a special, tiny compression gauge that wasn’t much bigger than a spark plug; so again, this is no problem either. Some guys have rope sheaves off other motors, that they put on the 4.5 flywheels with long screws into the flywheel puller holes, to do these tests.

Long live American manufacturing!

[elgin2]

Those Mercury compression gauges are on oldmercs.com.

[chris-p]

Well according to the old manual it should be in forward gear for this model to install the gearcase. Seloc though, so who knows.

[billw]

The manual, even Mercury’s own, always says forward. I guess this is because when in neutral, the gear case wants to pop into forward from spring pressure, if jostled enough. I dunno. I like doing it in neutral because the splines are always closer to being aligned that way. I’ve tried both ways and I like neutral better. Just my opinion.

Long live American manufacturing!

[thepetrolist]

My ’72 Merc 200 requires to be assembled with the forward gear engaged.

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