merc 200 outboard

[ara]

I recently purchased a 1974 23 foot mako with a mid 1980's 200hp black max. (Black cover with brown lettering and fake leather trim). It is my second mako, but my first merc outboard, I previously has a Yamaha outboard. I am finding that the merc 200 has trouble idling when in gear and often cuts out when I am either in no wake zones or docking. Other then this idling and low rpm problem the engine runs very strong throughout the power band. I have run through several tanks of gas and changed the fuel filter. Changing the plugs seemed to help the first trip out, but the engine is back to its old ways. I run aprox 40-1 premix and 93 octane gas. <br /> I have been told that old merc outboards don't run well at low rpms's, but I find this hard to accept. Could it be fuel, timing, poor compression. I am out of ideas and any suggestions would be helpful.

 

[shelbydriver]

Re: merc 200 outboard

Have you gone through the carbs lately. I thought outboards run 50-1? Maybe the low speed idle jets have something in them.Mayebe you need to just turn up the idle speed some.

 

[orca]

Re: merc 200 outboard

G'Day, Some of these merc V6 motors had problems at slow speed if the idle relief ports were below water, try idlying with the motor trimmed up slightly.

 

[Dhadley]

Re: merc 200 outboard

87 octane is the correct fuel. You mentioned you changed plugs but didnt say which ones you put in. NGK's are the correct brand.<br /><br />Good luck!

 

[ara]

Re: merc 200 outboard

This is all very helpfull and very much appreciated. I used new NGK plugs and have thinned out the mixture to about 50 to 1. The engine runs at about 1200-1500 rpms and that is the lowest rpm's that I can get the boat to idel. This produces about 7-10 miles per hour andthe engine is very inconsistant at this speed. it will ussually cut out after a little while of coughing and gargaling.Before I rebuild the carbsI will definately try running with the trim motor up a little bit. Any idea why that is the case with some of these motors? Also every time I drop the engine in gear from a high idle to speed to prevent the engine form dying does this cause major gear damage in the lower unit? It can't be good for it. Thanks and hopefullyI can get back to idling in those no wake zones and catching some fish while I'm trolling. ARA

 

[ara]

Re: merc 200 outboard

How difficult is it to rebuild the carbs? How much would a fair mechanic charge to do this for all three carbs?

 

[dakk1]

Re: merc 200 outboard

ara--I rebuilt the carbs on my 1985 Mercury 150 recently and it was a fairly straight forward procedure. However, a manual seems essential if you've never done it before. My local Merc dealer suggested replacing the inlet needles and inlet needle seats and gaskets of course. These parts cost me aroung $100 plus I bought a gallon of carb cleaner to soak them in for about $13. Another boat mechanic told me he would rebuild them for $150 but did not specify what parts if any he would replace. In light of what I paid for parts, he probably was only going to do the gaskets and clean everything else. The gaskets for the 3 carbs was less than $20....Dave

 

[sharkcat]

Re: merc 200 outboard

have you checked the synchronization/timing etc.This maybe the problem.

 

[JerseyJim]

Re: merc 200 outboard

i have a similar era 200HP black max, and mine shakes like a son of a ***** at idle. <br /><br />All older big V6 mercs SHAKE at idle, but you should be able to get a 750rpm idle no problem. <br /><br />Also, do you know how to throttle the engine idle up while in neutral? <br /><br />Hell mine starts without even choking it.

 

[kingsbiship]

Re: merc 200 outboard

You mite take a look at the reed valves while the carbs are off. weak reeds can effect the idle!