1970's 20hp merc

[rocktimr]

I Have A 1970's 20hp Merc Outboard And I Need To Know If This Motor Has A Sheer Pin And Where It Would Be Located

 

[Chinewalker]

Re: 1970's 20hp merc

No, it does not. It would have a splined shaft. What is it doing? Or not doing?
- Scott

 

[rocktimr]

Re: 1970's 20hp merc

Was Headed Off The Lake And I Had It Wide Open Then It Just Reved Up Like It Poped Out Of Gear, It Idles Fine But When I Put It Into Gear It Seems Like The Props Not Spinning, And It Just Boggs Down When Its In Gear, When I Shift Into Nuetral It Runs Fine, AND IN REVERSE IT BOGGS DOWN ALSO WHEN I GIVE IT GAS

 

[Chinewalker]

Re: 1970's 20hp merc

Sounds like you may have a spun propeller hub. Easy enough to check. Mark a line on the prop nut and the propeller with a Sharpie. Run the motor in gear and note whether your marks are still in line with each other.

A spun hub occurs when the rubber bushing between the inner and outer hubs of the propeller starts to slip. Only fixes are to either have the hub replaced - any good prop shop should be able to do it for you, or replace the propeller.
- Scott

 

[Yepblaze]

Re: 1970's 20hp merc

Sounds to me like you might have two different issues.

One being the bolt hole above propeller where the nut is placed over a stud to hold the lower unit in place can sometimes "pull through" leaving and open area where exhaust can flow right by the nut entering the propeller wash and causing cavitation at anything above high idle speed.

And for #2, perhaps a fuel issue that can appear if the fuel line is allowed to come into contact with the carb body causing a pinching effect to wear through it.

 

[rocktimr]

Re: 1970's 20hp merc

Thanks For The Info