1984 Mercury 200hp timing

The engine is a 1984 Mariner 200hp. The engine idles perfect but when you go to get out of the hole it takes approximately 70 yards for the boat to get on plane. The engine appears to be stuck at 3000 rpms then finally decides to plane out. The engine used to scream and have no problems getting to 5800rpms with the current prop at high altitude. The stator, spark plugs, fuel pump, fuel bulb, fuel hose, fuel filter, and new fuel have been replaced. The carbs have been rebuilt. The engine has 200hours but set for 8 years. The red wire coming from the idle and timing module were heavily corroded on both ends. When I attempted to find a replacement I found the module is no longer manufactured and it was advised to do away with the module since they are not needed anyway. I am in the process of setting the timing both idle and WOT. The boat lives at 6000ft. above sea level. Do I make any adjustments for altitude when setting the timing? I realize there may be other issues present, but I am attempting to eliminate one problem at a time for an older gentlemen as inexpensively as possible. Thanks for your assistance.

was it rejetted 4 6000'??? sounds like its overpropped.

Mine does the same thing. I think the exhaust is filling with water, and it takes a while to blow it out. Cause if i come off plane, and don't let it idle all the way down, it will blast back off. I really don't know if that is right or not though.

The carbs were rejetted to run at 1000ft when rebuilt but the engine was recently brought back to 6000ft. The prop is the same but a used lower unit was purchased when the engine began to sit for 8 years. I have wondered if the ratio was different than the original resulting in being overpropped. Is there some way to determine the gear ratio on the lower unit? Thanks!

I should have added the engine was performing the same at 1000ft and one of the reasons why it was brought back. That and the individual just wasn't using the boat.

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Originally Posted by ufish2

. Is there some way to determine the gear ratio on the lower unit? Thanks!

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Mark the flywheel, and mark the propshaft.....turn the flywheel one revolution....did the propshaft turn one complete relolution?...if it did, its a 2.1 gear....if not, 1.87

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Originally Posted by WATERWINGS

Mark the flywheel, and mark the propshaft.....turn the flywheel one revolution....did the propshaft turn one complete relolution?...if it did, its a 2.1 gear....if not, 1.87

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If you turn the flywheel 1 revolution and the prop shaft turns one complete revolution, wouldnt that be a 1:1 ratio?

Ran home at lunch to turn the flywheel. Turning the flywheel two revolutions resulted in the prop turning one around plus 1 1/2 inches. Does that provide a clue to what the ratio is? Anyone have ideas about where to set the timing at 6000ft without the module? Thanks again to everyone for advise.

ooops...yep....I guess what I should have said was TWO turns of the flywheel should be one turn of the propshaft....

If its not even with each, it would be 1.87 ....

I would say 1.87 gears....

I don't know if the altitude has anything to do with the timing...but I am a sea level kinda guy....I always set mine at 25° with the timing advance module in the trash can...

As was said set max timing to 25, idle timing if they give a range like 2-7deg ATDC set at 0-2 deg. If the jetting is stock you can jet down as they come jetted for sea level-2500ft, manual says .002 smaller 2500-5000ft and .004 smaller 5000-7500ft. Cutting the heads to 34cc will help lots at 6000ft, Merc also had high altitude gear set that was 2.0: 1 for over 5000ft. We boat at just under 3000ft and all our carb motors ran much better jetted 1 size leaner as the manual recomended.

Dave

go to a dealer( @ 6000') and get his sugestions for rejetting. reprop--- youll expect 4-6 inches less than sealeval.