Mercury 200 HP Compression

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Duke01

Member
Launched my V20 cuddy today on Lake Erie which gave me a chance to check compression on my 1980 Mercury 200 HP. She is hard to start, but runs well. 1570 hours. Compression is as follows: 130, 135, 120, 125, 125, 115. I tested hot. My understand is that the overall range should be within 10%. I am close to 15%. Any thoughts regarding these numbers?

Thanks, Duke
 
Actually for a 40 year old motor, that s not too bad. If it runs ok, I d just run it. When u checked compression, did you have the other 5 plugs out and the throttles open?

As far as hard cold starts, does that motor have a choke or an fuel enricher system? Could be something not working in that.
 
All plugs were removed, but the throttle was not wide open.

The only choke that I am aware of is with the key, push in as you turn the key to crank the engine.

Carbs were all cleaned good last year.

As you say Phat, my plan is to run it this year and forget about it. She never stalls, just needs a little starter fluid and off to the races. I have a new Tohatsu 9.8 for insurance and trolling.

The other starting issue is that the starter only engages the flywheel about 50% of the time. Not sure to do about that.
 
When u press the key in to start, it actually spritzes s little gas in the throat of the carbs not sure if all three or just middle one. It s not a choke butterfly in the normal sense of the word. I would verify that all of that system is working.

I had a 84 & 94 carbed merc 150, they were both a little finicky when cold. What i would do is pump ball till hard, turn key on and press in 3 times, advance throttle lever about 1/3 up and then spin starter. After they were warm, just bump the key.

I d be careful with the starting fluid, usually not a friend of 2 strokes.

Maybe some of the really smart guys will come along and chime in
 
hit the cylinders with a can of power tune decarb spray. Let it set over night, cranks it up, blow all the power tune out and recheck your numbers. If the carbs are set up correctly, it should start from cold by just holding the key in while spinning the motor over, once it hits, it will stall, then try to restart, momentarily holding the key switch in, it will start, but try to die out, when it stumbles, bump the key switch in for a sec, it should pick right back up, after about 30 secs it should idle on its own. Let it warm up a bit before putting it under load
 
Thanks for the tips regarding the starting sequence. I will try what you have both described. I don't think that I have used a consistent approach regarding pushing the key in while cranking thus far.

I was not aware of Quicksilver Power Tune. Just placed an order.

Thanks again, Duke
 
Merc 200 Start

Regarding my starting issue, I have started (without starting fluid) on my last two outings. Pushing in the key three times before turning the key switch, while throttling up a bit with the key in. Now I just need to fine tune the process.

Thanks again...
 
Duke01 said:
Regarding my starting issue, I have started (without starting fluid) on my last two outings. Pushing in the key three times before turning the key switch, while throttling up a bit with the key in. Now I just need to fine tune the process.

Thanks again...
Click to expand...

the only time pushing the key does anything is when you are spinning the motor over, or if you just pump ed the primer bulb up good and tight. All pushing the key in does is open a valve that allows fuel to flow in behind the carbs, enriching it. It rely on the fuel pump or residual pressure in the line to push the fuel in. Try holding it in while spinning the motor over
 
Like Spare said , the ball pressurizes the system and the fuel pump move the fuel. If you haven t change the diaphragms in the pump in a while, might be a good idea to do so.

Pretty cheap and easy to do. I would also use OEM merc parts
 
Mine always gave me a fit first start of the day and then would run fine the rest of the day with just a bump of the key.

Best way I found of the cold start was make sure the bulb was Hard, advance throttle about 1/3 of the way out of gear and start her up. Might take a few turns of the key but once she fired let her sit that way for a minute or so and then I was good to go.

Another thing I learned if I turned both batteries on she always started quicker.

My compression numbers were 125-130 across all 6 before I lost the 1 cylinder
 
Very similar situation for me, tough to start, but never stalls, runs fine, idles fine. I troll with a new Tohatsu 9.8. Good luck on your search for No. 4
 
Duke01 said:
Very similar situation for me, tough to start, but never stalls, runs fine, idles fine. I troll with a new Tohatsu 9.8. Good luck on your search for No. 4
Click to expand...

How do you like the tohatsu? Im thinking of buying one when they go back on sale.

I’ve got a great running two stroke but a electric start 4 stroke sure would make things easier without the extra gas tank in the boat and the ability to charge batteries while Trolling
 
Tohatsu Kicker

I really like the Tohatsu 9.8 kicker. It is very quiet while trolling at 2 mph. I can steer with the kicker, or use the big Merc as a rudder.

I tested my max speed with the V20 and it is around 5.5 mph +/- for conditions. Max fuel burn is 1 gal/hour. I carry 2 extra 3 gallon tanks in the cuddy. That gives me a good range in case of an emergency, and a little ballast up front.

If you have the extra $, I would opt for the power tilt as well. Mine is 90 lbs with 20" shaft and electric start. Power tilt will add a few lbs.

Research from a couple years back told me that Merc uses Tohatsu for outboards under 40 HP. I am a red, white and blue guy, but no american options these days.

$2,400 two years ago from Dinghy Concepts in Detroit.
 
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