1967 20hp johnson

J

jsmzdlt

Cadet

Joined

Jan 20, 2003

Messages

15

• Feb 3, 2003

• #1

i have a 1967 20 hp johnson.when i throttle up it seems to slip like its a clutch slipping but i dont know if it has a clutch? i was told to check to see if it was a spun hub so i blocked the prop and tried to turn the flywheel and i couldnt so im open for more suggestions from anyone who may be able to help.if i run at a slow speed it acts fine its only when i throttle up it also seems to get hot when this happens.thanks to anyone who can help

 

Joe Reeves

Supreme Mariner

Joined

Feb 24, 2002

Messages

13,262

• Feb 3, 2003

• #2

Re: 1967 20hp johnson

Has this engine ever run properly on the boat in question, or is this the first time you've tried it? A possibility is that you are running a short shaft engine on a boat that requires a long shaft engine.<br /><br />The cavitation plate (the plate just above the prop) should be approximately 1" below the bottom of the boat at the transom. If it's higher that the bottom of the boat, you will have the exact problem you describe. Let us know what you find.

 

JB

Honorary Moderator Emeritus

Joined

Mar 25, 2001

Messages

45,907

• Feb 3, 2003

• #3

Re: 1967 20hp johnson

Howdy.<br /><br />Well, if your prop hasn't spun a hub you are probably ventilating.<br /><br />Check that the anti-ventilation (Often incorrectly called cavitation) plate is even with the bottom of the boat. You may have a short shaft (15") engine on a long shaft (20") transom.<br /><br />Let us know.

 

JB

Honorary Moderator Emeritus

Joined

Mar 25, 2001

Messages

45,907

• Feb 3, 2003

• #4

Re: 1967 20hp johnson

Sorry, Joe. You posted while I was typing.

 

Joe Reeves

Supreme Mariner

Joined

Feb 24, 2002

Messages

13,262

• Feb 3, 2003

• #5

Re: 1967 20hp johnson

JB..... I've no problem with that my friend. Shows we think somewhat alike.

 

J

jsmzdlt

Cadet

Joined

Jan 20, 2003

Messages

15

• Feb 4, 2003

• #6

Re: 1967 20hp johnson

yes i have run this motor for some time on this boat and never had a problem till this year.and it doesnt do this slipping all the time just periodically.it is starting to do it more often

 

O

ob

Admiral

Joined

Aug 16, 2002

Messages

6,992

• Feb 4, 2003

• #7

Re: 1967 20hp johnson

jsmzdlt,Have you removed the prop and inspected the shear pin?

 

J

jsmzdlt

Cadet

Joined

Jan 20, 2003

Messages

15

• Feb 4, 2003

• #8

Re: 1967 20hp johnson

i checked the shear pin and it is in good shape the only thing that looks unusual is there is a grove on the bottom of the head under the prop could that have anything to do with it. im sorry about the way i explain this but im not to sure of the proper names for all of this

 

O

ob

Admiral

Joined

Aug 16, 2002

Messages

6,992

• Feb 4, 2003

• #9

Re: 1967 20hp johnson

Groove could be indicative of propshaft bearing wear.Maybe the pinion gear has come loose from driveshaft,In any case it sounds like the lower unit needs to be dismantled and inspected.Parts may be an issue to locate.A rebuilt or used LU is another option.

 

J

jsmzdlt

Cadet

Joined

Jan 20, 2003

Messages

15

• Feb 4, 2003

• #10

Re: 1967 20hp johnson

thank you i will check it out. thank you again

 

T

TORX

Cadet

Joined

Jan 3, 2003

Messages

10

• Feb 4, 2003

• #11

Re: 1967 20hp johnson

put another prop on you have slipping hub when it get hot it slips when it cools it bund again and it will get worce more you use it<br />if you sher pin is bad you will go now where is ether works or it does not