1969-71 merc 20hp

[JasonB]

I have an old Mercury 2cyl 20hp, probably a '69-71. It was running when stored in a shed 7 years ago, but the carb needed rebuild. This engine has some sentimental value as it is the motor my brother and I used as kids so I would like to get it back running and redone. When it was put up, the bearings on the crank were supected to be worn out, and it may have only been running on one cylinder. After I clean teh mouse nest out of it, I'm wondering if my best course of action would be to pull it down and check the cylinders for any damage and maybe replace the bearings.<br /><br />How hard is this motor to work on? I have rebuilt a car engine and have tinkered with my crossflow Johnson, so I'm pretty comfortable tearing into things. I havn't looked at it yet, but I'be been told there is no head to remove and taht the block has to be split?

 

[Chinewalker]

Re: 1969-71 merc 20hp

Hi Jason,<br /> Step 1 - get yourself a service manual. The aftermarket ones will likely cover enough of the basics to get you through, and what they lack in specifics we may be able to help you with here.<br /> Those old 20s are good motors and still plenty of parts out there for them. I've found eBay to be a good source of odds and ends for them, too. <br /> One thing I would check off the bat would be to see if you have the Lightning ignition (traditional points, coils, condensers under the flywheel) or the Phase-Maker ignition (green donut, two sets of points under flywheel, coils on motor block). The Phase-Maker ignition works fine when it works, but if it fails, parts are VERY expensive if you can find them at all. If you post the serial number I can nail down the year and likely ignition system...<br /> Waterpump kits and carb kits are readily available through Sierra aftermarket dealers (NAPA, West Marine, etc.).<br /> Bottom line is to have fun with it!<br />- Scott

 

[JasonB]

Re: 1969-71 merc 20hp

I have scoured the motor and can't find a serial number on the clamp, nor do I see it on the powerhead anywhere. I see a P/N on teh "powerpak" and a 5-6 digit number on a big flat place on the block. I think this motor is a frankenmotor.

 

[andrewkafp]

Re: 1969-71 merc 20hp

What does the cowling cover look like. Colours, markings ?

 

[JasonB]

Re: 1969-71 merc 20hp

The current cowl is trimmed in red, but my brother may have swapped it from a blue one years ago. It has the crome faceplate and Thunderbolt igniton. Single carb. There is an odd looking spot on flat side of the block on the right side of the motor that loojs like a threaded post to mount something to. It has multiple Keikhafer(sp?) markings on it. <br /><br />Is there a specific spot on the powerhead taht may have some useful info on it? I would take a picture, but I suspect that wouldn't help too much.