mark 20H tragedy

[tsutter]

Hello all:<br /><br />Got a 1955 Mercury Mark20H racing motor. Needs work, so I was checking compression (pulling loosely, because side cowls were not attacheed) and pulling the pull cord with the comp gauge in. About 4 pulls into it, I noticed a piece of metal drop to the floor (it hurts just to recall this). The piece that broke off was the metal connector that anchors to the fuel pump, top cowl and starboard side cowl. It torqued off from the pulls. However, I didn't pull that hard, and when I looked at where it broke, it looked as if this piece had been welded before.<br /><br />Well, I guess to make a long story short, what are my options? Have I toasted this motor, or is there a way out of this (re-welding?)<br /><br />Love to hear from y'all. Hope your all having a great weekend.<br /><br />Thanks in advance.

 

[FlyBoyMark]

Re: mark 20H tragedy

Yeeeesss it can be welded and be good as new if done properly. Alighn the two parts where they broke and fabricate some sort of metal fixture to hold the two pieces in alignment. In addition the two pieces must be beveled to a point or edge equally on all sides depending on the shape of the part. Glass beading of the immediate area around the break is suggested before beveling. pre heat by sooting up the aluminum with acetylene on ONLY with torch. Adjust to neutral flame with oxygen on and heat only enough to burn away soot. DO NOT USE a rosebud or very large gas welding tip!!! Then she's ready to weld with 4043 alloy filler in this case. Person TIG welding should use a 5/8" gas cup and 10-15 cu.ft./hr. argon flow rate, 3/32 2% thorated tungsten preped to blunt pencil point(will properly ball up when welding process starts). Cover with fire blanket and let cool slowly. clean up with 4.5" grinder with sanding disk using candle wax or F-26 Formax stick or die grinder, dremel, excetra...Fixed stuff like this in my welding business for 20+ years...

 

[Chinewalker]

Re: mark 20H tragedy

Hi TSutter,<br /> Is this the bracket that attaches to the studs on the crankcase, near the carb, or is this one of the bosses on the cowling itself? Not sure which one you broke. In any case, there are no brackets on the motor itself that aren't replaceable - they're all bolted on in some fashion. The 20H cowl and recoil mounting brackets are all common to the Mark 15, Mark 20 and Mark 25. The only difference on the front porstide bracket is that the 20H bracket has some threaded holes for the timing indicator to mount onto.<br />- Scott<br />

 

[tsutter]

Re: mark 20H tragedy

Thanks FlyBoyMark and Chinewalker:<br /><br />I am encouraged by your responses. I went back out to look at this and it appears that this bracket is removable. It has two threaded holes through the bottom for attachment to the powerhead. Then there are two threaded holes on the side that attach to the two holes on the starboard side. Then there is one threaded hole facing up on the top where the fuel pump bracket fits over and both of these support one of the studs from the top cowl. There is no attachment for the carb on this bracket - just threaded holes for the powerhead, starboard side cowl (right, looking from the back of the motor to the front), and top cowl. I can also send a pic.<br /><br />Thanks again fellas.<br /><br />P.S. Chinewalker - I run a 1969 Merc 350 electric start on the back of my fishing boat and it just purrrrrs <br /><br />Take care.

 

[tsutter]

Re: mark 20H tragedy

Oops:<br /><br />Sorry Chinewalker - just reread your post and, yes, it is the bracket that attaches to the crankcase. It also attaches to the starboard side cowl and there is a threaded hole on the top for attachment to bracket on fuel pump and top cowl stud.<br /><br />Thanks.

 

[Chinewalker]

Re: mark 20H tragedy

Hi Tsutter,<br /> That "fuel pump" is actually a fuel filter. The fuel pump is attached the the port side (looking forward) of the crankcase. If your 20H is original, it will not have a fuel pump at all and will use a pressure-feed system that requires a 2-line tank. Being that yours has the fuel filter, I would suspect that it still has the N-2150 Carter Carb. The later Tillotson KA-7A had a filter built right into the top of the carb.<br /> In any case, the bracket you're speaking of shouldn't be too hard to find. I would start at www.oldmercs.com and get yourself a copy of the 20H parts list and owner's manual. I would also invest in the gearcase cone wrench, as you will need to grease the cone bearings on a regular basis - most racers did it after every day of racing. Your motor has quite a bit of value so it's well worth spending a little money on it. I will look to see if I have one of the brackets...<br /> Drop me a line if you have any questions about your motor... (csr112-n@prodigy.net).<br />- Scott (owner of one unconverted 20H and one converted Cornpopper 20H)