Merc 20 hp Multiple Questions

[TarHeel]

As a new participant in this forum, I have found the answer to many of my questions. Thanks to all of you who take the time to read, contemplate, and respond to our questions about our motors.<br /><br />I have a 1973 Mercury 20 hp that runs good.<br />Question1. Last evening I drained the lower unit and replaced with fresh lower unit lubricant. The old stuff was coffee colored and obviously had water in it. How could water get in this area and how serious is it?<br /><br />Question 2. Where is the water pump located on this engine?<br /><br />Question 3. How is the fuel/air ratio adjusted?<br /><br />Thanks in advance for your response.

 

[ehenry]

Re: Merc 20 hp Multiple Questions

Water in the lower unit is something that needs to be addressed. It can get in there in a number of ways. The seals in the prop shaft may be leaking or the seals o-ring in the water housing my be leaking.<br /><br />The water pump is located in top of the lower unit. Drop your lower unit off and you will see a housing where the drive shaft comes out of the lower unit and goes up to the power head. Thats your water pump. <br /><br />I don't know about the air/fuel adjustment I've never had to adjust mine. I'm sure theres an adjustment screw on the carb there somewhete though.

 

[TarHeel]

Re: Merc 20 hp Multiple Questions

E.F. Henry,<br /><br />Thanks for the information

 

[neurofish]

Re: Merc 20 hp Multiple Questions

I have a 1986 25 horse Merc. I imagine that the layout is similar. The fuel mixture screw is directly above the main air inlet hole facing you as you pull off the cowling. Start by turning all the way in, then out 1.5 whole turns. Adjust from there.

 

[BKool68]

Re: Merc 20 hp Multiple Questions

the water can also leak in at the gaskets to your drain and fill plugs.

 

[ehenry]

Re: Merc 20 hp Multiple Questions

This is what I love about this forum....somebody is going to remember what you forget to mention. Thanks Bkool68

 

[johnkc]

Re: Merc 20 hp Multiple Questions

hey tarheel ,these motors were notorious for the drive shaft rusting up at the seal in the water pump base and leaking there.also the shift shaft will rust as these were not stainless steel yet, and the shift shaft seal will leak. so.......... might as well replace all of the seals, if it isn't just your drain and fill screw gaskets. if you find that the drive shaft has rust you can fit the seal area with speedy sleeves instead of locating a new , good shaft.

 

[TarHeel]

Re: Merc 20 hp Multiple Questions

Thanks everyone for the information. I have so much to think about now I probably won't sleep at all tonight. Seriously though, I really like this motor for some reason. It seems to have a will to run and I want to prolong its life as long as I can (or untile the money runs out)(or the wife leaves me)(or I break something really important).<br /><br />Thanks again.