Keyway size

[geary]

Guys,
About to start on an impeller replacement on a Mk28, after watching a couple videos they say the impeller for it is the same as the Mk20, 25, 30 but it has to have the keyway notched out to accommodate a square key ! But didn’t say how wide or deep the keyway should be ? Anyone know what size key they use ? My engine is not the 28A, just the standard Mk28

Geary

[dave-bernard]

both motors are the same impeller just file the keyway to fit the drive shaft make sure it has a loose fit.

[billw]

I looked at four of my spare shafts with the keys in them. The keys wear, so it’s tough to call a number exactly, especially just using a machinist’s rule. If I had to call it, I would say 3/32″ wide and deep. Most of us don’t have the capability to actually machine a keyway in an impeller; so we just do like Dave said. Use a file and make it fit. A loose fit is needed so that the installation is not botched and so that the impeller can easily center itself in the pump housing, as the engine runs.

Long live American manufacturing!

[geary]

Thanks Dave & Billw, I kind of suspected that would be the case , file and fit, file and fit ! What a great resource we have in this club, good answers from great people !

Geary

[dave-bernard]

I use a small flat file and grind to fi in the hole. use the edge mine was correct width.

[Author]

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