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Late 70’s Mercury 200 20hp advice

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DolmarKarl

New member
Hello all, I would like to ask a bit of advice on an older Mercury motor. This is my dad’s 200 20hp motor that he bought in the late 70’s. I put a new water pump into it, carb kit, plugs, new gear oil for the lower unit and I am in search of some ears to tell me if this motor sounds sea worthy? I have run it for approximately 20-30 mins, it shifts fine and the water pump is working very well. I am unsure about the idle speed for this particular motor and would appreciate any input as to how it sounds. This is something I wanted to fix up for my dad who said he wanted to take it out before his time is up in this world. It would mean the world to me if I could get this thing going for a good trip on the water with him.

here is a link to the video of me testing it
https://youtu.be/Ohc5Hn3R27E
thank you for your time

-Karl
 
I am sorry to have to do a reply on my own post but I dont have editing capabilities yet. Just to simplify, my questions are: what do these old mercs typically idle at( I have a good tachometer to dial it in)? For the idle mixture screw, do you set at 1 1/2 turns out to start with then adjust to be just a tad rich(sort of similar to the high speed jet on a 2 cycle small engine?). I am sorry for all of the questions on this old motor, it is about double my age and finding a competent manual is rather difficult. Just looking to gain some more knowledge to keep it going in the future. I would greatly appreciate the help if anyone has experience with these guys older mercs. Thanks
 
flyingscott said:
Do a cylinder drop test on it. Sounds like it might be running on one cylinder
Click to expand...

just performed the drop test while running. Both cylinders are firing, spark is strong with the spark tester, and brand new plugs. It cranked on the first pull, no choke needed. Just the primer
 
I did notice when I pulled the plug boots off that the metal portion on the park plug boot was loose on the plug. It seems like it was flooding out intermittently with the coil wire not being connected securely. Once I tightened that up, and de-flooded the cylinder it seems to be idling smoothly. Any chance I could replace the plug boots with something like an atv plug boot? Are these boots the screw on type or fixed to the coil wire? Thanks
 
Any good ways to tell if it is running too rich? Im assuming these old motors smoke a good bit no matter what. I have tweaked the mixture screw and have it in a place where it will idle and rev okay. I polished the seat with some lapping compound and I tried to get the float level as even as possible. It is not leaking up past the seat when I hit the primer bulb because it gets firm and tight. I might pull out the carb again and adjust the float a tiny but more if yall think it is worth it. I just want to be extra sure this thing is ready to go before I get on the water. I can tell you from experience, fat southern dudes and paddles dont mix well:eek:
 
The low speed is adjusted while underway with the engine warmed up just off idle, it should accelerate without bogging; if it bogs adjust the needle until it is smooth. You can buy the coil wire assembly from here https://www.oldmercs.com/category_s/2018.htm.
A good move is to run it on synthetic oil and gear lube.
It sounds good to me considering the bucket is containing the sound, when it's in the water it will be quieter.
 
Quicksilver said:
The low speed is adjusted while underway with the engine warmed up just off idle, it should accelerate without bogging; if it bogs adjust the needle until it is smooth. You can buy the coil wire assembly from here https://www.oldmercs.com/category_s/2018.htm.
A good move is to run it on synthetic oil and gear lube.
It sounds good to me considering the bucket is containing the sound, when it's in the water it will be quieter.
Click to expand...

thank you for the link and the advice as well sir. It has not flooded out on me a single time in tests I have done at home. With a new water pump, good synthetic 2-cycle oil and fresh gear lube with o-rings around the drain/fill plugs, worst case scenario is I haul it back home from the lake and tweak the carb. I will take it out on the water and really open her up. I wish I could at home but I dont have muffs and I will really get a feel for it when its truly under a load. I love this old motor and it has a lot of sentimental value to my dad. If it starts dropping spark on me I think I will change the coil wires but some plyers to tighten the ends and dielectric grease should keep a crisp connection. Im gonna take her out this weekend, pray I dont throw a rod and have my dad fill the boat up with tears afterward :cool:
 
Don't use O-rings for the LU plugs when you tighten the screws they squeeze out (I've seen this), there are fiber ones from Mercury for that application.
 
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