I have a 1969 20hp that I rebuilt and I was out testing it today. The motor was running great but at some point I would give you motor gas and the engine would rev up but the boat did not increase in speed. It drives at idle though. Any suggestions?
Hi wg. Cool motor. I have a '66 20 hp Johnson myself. When it comes out of gear, does it feel like you're hitting a log, or submerged object or is it more of an over rev situation? If it feels like you're hitting something, then you probably have a worn clutch dog in which case you'll need to drop the lower unit and open the gearcase. If it isn't too worn you can flip it around and reuse it. You may slip in REV, but most people don't use it very often so you may be ok, otherwise you'll need to check ebay, marineengine.com, aomci.org or ask around here in the forums for a new one. If it feels like an over rev, you probably have a spun hub on your prop. You'll have to either get a new prop or get yours rehubbed at a shop. Here are some handy links to help you keep your motor running.
While out at the lake before you get the boat in the water take a permanent marker and draw a line starting on the prop nut down to the prop. Or as I did when I had this problem take a pocket knife and carve a small one. Repeat the problem if the line is broken then you have a spun prop hub. If it is not then you may have other issues. If like kfa says and you feel like your hitting a log then I agree with the clutch dog. I had that problem as well with a my 69 20 hp And with my big twin 40. Both times same issue started at high rpm by the time I got back to the ramp it would barely move my past a crawl without slipping. Luckily I have donors for both these motors and had parts available.
Either way. New prop 80-110
Rehub local prop shops around here are 35 and up
eDIT
Do not use the line trick in a bucket
Nah, no way to rehub it yourself. You need special tools. You can either get a new prop, find a replacement online, or off of a donor motor, or take it to a prop shop to have them rehub it for you.
That's a negative the rubber boot around the hub is a percentage larger than the hole in the prop. Requires a what's called a cone and a press. I was looking into doing mine myself until I looked into it further and called a couple of prop shops. look into local prop shops and and see if there is one near you. I'm all for a rehub my local guy will also do a recondition job for 45 plus any welding required
I will see if he does any mail order stuff. Send me a pm if you need their info
