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skunked_once

short shaft conversion and water pump problem?

4 posts in this topic

I have a 1980-81 9.8 Mercury and the last time I was out I ran through a shallow, gravely spot. Fortunately no prop damage but I noticed later that when I throttled down to trolling speed, the motor quit pumping water out of the pee hole blush.gif. It pumped great at high speed but only when the boat was moving. I'm assuming that I damaged the water pump impeller and need to replace it next spring. Is this a job I can do without a repair manual? I'm handy with tools but I need to know if there are any pitfalls to watch out for. The motor is a long shaft which is part of the reason I hit the bottom. How difficult would it be to convert it to a short shaft? Can I just switch the bottom end from a short shaft motor? Anyone have a short lower end to sell or trade? I've got all winter to decide what to do which means that I'll be frantically taking care of this at the end of May. Any and all advice, whether followed or not, is greatly appreciated!

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Go to partsexpress dot mercurymarine dot so on and so forth. They have a schematic/drawing of the motor that shows what goes where.

Does your prop seem to be too much below the keel of your boat. A short shaft may put your prop above the water line of the boat.

Finns.

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Measure the height of your transom where motor hangs.

It can be for 15" (short) or 20" (long) shaft. If you have Long (20") you cannot switch to short shaft or your motor will be out of water almost completely.

If you need to reduce your height, you will need a new/used lower unit or take it to a dealer and have driveshaft switched to short, also if your middle section does not have the "long shaft" removable section, it witll be impossible.

Either or it will cost you more than the motor is worth, and by a long shot.

There are devices out there that help saving propeller, and lower parts of motor, from hitting bottom.

Replacing water impeller doesn't cost much, if you learn to do it yourself it will be A LOT cheaper.

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Finns and Valv,

Thanks for the quick replies. I should have mentioned that my boat is an old 60's Starcraft aluminum and my short-shaft 5.5 Johnson fits it just right. I have a 2" board on top of the transom with the 9.8 long-shaft but it's still too long. Unless I run across a cheap short lower unit, I will have to just be more careful. Now I have all winter to find the parts diagrams and figure out how to tackle the job in the spring. Now if I can only dig out my portable buried in the garage....

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