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mk30h
04-18-2005, 03:10 PM
Hey guys,
I have a question that I'm sure one of you lads will be able to answer. I have a nice 1970 Merc 500, with a both short and longshaft housings. I it was missing the gear case etc- but everything else is mint. Picked up a complete lower unit from a Merc 402. The housing is the same, but is the gear ratio as the 500. Seemed to be on one old brochure I saw, but I am not positive.

Is there any model years that would be perferable to run on a very light runabout like a old Arsitocraft? What years and models would be best? I knwo that a lot of 402 and 3 banger 60-75 mecr lower's are around as the engines seemed to die rather quickly.
Just checking in the scrap pile behind any dealers lot will produce a hell of a lot of the 3 cly clamshells.,

Thanks
Steve

2us70
04-18-2005, 03:59 PM
If that unit is a 2:1 bolt it up. My McCall ran a lot better with the lower ratio unit than with the older ones.

mk30h
04-19-2005, 03:32 PM
Thanks 2us70,
Thats the info I needed, I'll check the ratios on the engines and see what is what. I'll post some picks of the engine in a few weeks. Looks like it came out if the box yesterday. There was not even a film of exhaust in the tuner.
I love these 4 bangers, smooth, easy on gas and seem to run forever

2us70
04-19-2005, 04:04 PM
I owned and raced several Merc 500s and worked on a few others and I found them to be great motors. The one thing that eventually caused failures in a number of those old 50s was pinhole leaks into the cylinders from the water jacket right next to the spark plug boss. It may be from use in salt water since all of the motors I saw this problem on were used at least partially in salt water. Other than that if you keep a good water pump in them they pretty much run forever.