1974 20hp Mercury issues

[ol sarge]

First, Happy Fourth Of July! I just got back from a morning of fishing. I bought this motor this spring and have only had it on the water 3 times now. The issue I am having is getting it up to WOT. Sometimes it acts like it is slipping and others it will go like heck. This motor was completely reconditioned and had a 90 day warranty on it. This issue does not happen all of the time, but when it does, the RPMs go way up and it seems as if the motor is not turning the blade. Could it be slipping out of gear some how? This is an old motor and it is sometimes hard to find neutral. I am still on the original tank of fuel that I bought in May ( 93 octane, no ethanol and added marine stabil to the mix), I run a fuel filter on the main line and that is new as well. This motor starts on the first or second pull every time. I noticed that there is a knob on the tiller handle that you can adjust. Could this have anything to do with my issues? Any ideas on what might be going on and any solutions would be greatly appreciated.

Tim

 

[MDCrappie]

Sounds like either the prop is slipping or the prop hub is slipping. Since it "goes like heck sometimes" my guess is the prop itself is losing bite. Might try lowering the motor on the transom if possible.

 

[Rich27028]

where does the anti vent plate sit in the water - and in relation to the keel --

could also be prop hub

 

[crazymanme2]

Knob on tiller is for friction for the throttle.
Sounds like prop is cavitating.

 

[ol sarge]

Here are some pics of were the motor sits. I don't think there is anyway to lower it unless you guys have some good ideas. Also, I noticed that there are bolts thru the transom that line up with the motor. Should the motor be bolted directly to the transom? Any suggestions? Thanks for the help.

 

[JoshKeller]

best test for hub slippage is to get some white out and make a mark on the hub and prop housing. take it for a run, and if they are no longer lined up, your hub is spun. Most shops charge around $50 to press in a new one, including the hub itself

 

[JMichael]

Up until early this spring I had a 1975 model of the same motor. Mine had a prop with a spun hub on it when I got it. From what I can tell the motor height in relation to the boat is OK so it's looking like you might have a spun hub. You can test it by marking it as mentioned about (although I'm not sure if whiteout will stick well enough for the test). As far as I know you are out of luck on trying to get a new hub pressed in that prop. It's my understanding that they don't make that 8 spline hub any longer. You'll have to locate a used or new old stock prop for it on ebay or somewhere.

 

[ol sarge]

Thanks for the assistance. Turns out it was a spun hub. I dropped the prop off at the shop this morning. I am buying a new prop and having the old one repaired. The new prop is $135 and to repair the old one is $30. I figure this way I have a spare just in case I would spin one. I think the prop was spun when I bought the motor. From what I have read, there is no real way to tell if a prop is spun until you put it in the water and run it. Thanks a gain for the assistance.

Tim

 

[JMichael]

ol sarge » Yesterday, 16:26[/url]"]Thanks for the assistance. Turns out it was a spun hub. I dropped the prop off at the shop this morning. I am buying a new prop and having the old one repaired. The new prop is $135 and to repair the old one is $30. I figure this way I have a spare just in case I would spin one. I think the prop was spun when I bought the motor. From what I have read, there is no real way to tell if a prop is spun until you put it in the water and run it. Thanks a gain for the assistance.

Tim

Nice, I wish I could have found that place when I had my 20 horse Merc. Do they have a web site? I sold the motor to a friend and I'll forward that info to him is they do.

 

[ol sarge]

The do have a website. Do a Google search for Powerhouse Marine in La Crosse WI. They are less than 100 yards off of the Mississippi and have a boat landing. I guess the carry so much since people are on the water and break something and can pull right up and get it fixed. The place he sent my old prop to get rehubbed is North American Propeller, Inc located in Schofield WI. I hope to keep this motor hummin for another 40 years God willing and the creeks don't rise.