We recently purchased a short shaft motor, only to realize that our boat requires a long shaft motor. If we continued to use the motor, would it damage it? Would it run slower than it should? Thanks in advance!
Only issue that I can think of is that at speed, it may not be able to pickup enough water for cooling because the LU is much higher than it should be relative to the bottom of the hull. Performance will definitely suffer, but how much is impossible to say.
Yes, here is a picture of it on our boat. When we bought the motor, we were told it was a 1980, but we think from our research it is more likely a 1970. Maybe we measured wrong, but we measured the motor at 15" and our transom at 20". Can you tell from the picture? Thanks in advance!
It'll run OK at idle or non-planing speeds, but as soon as you give it throttle and the boat attempts to come up on step, the prop will suck air and start to ventilate. Besides losing water pickup as previously mentioned.
Bay Marine made an extension kit for these motors, if yours is worth spending the $$$ on, installing a 5" extension might be the answer for you. Don't know if these kits are still manufactured, but you run across one on eBay every once in a while.
Otherwise you need a longshaft center section and lower unit (or the 5" extension stub shaft to put on yours), and swap over your powerhead. Lots more work doing it that way.
I couldn't see your pic at work but the motor definitely looks like a short shaft.
However, it also looks like the motor is sitting about right on the boat.
Are you SURE that transom measures out to 20"? You must measure from the center top of the transom where the motor sits, straight down to the keel (bottom center) of the hull.
Let us know what she measures out at and we'll figure it all out.............ed
1970 80hp mercury short shaft question
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