70hp johno problem

Hi Guys

I have a 1984 70hp johnson 3 cyl outboard i know its an old motor and it only has to last another 6 months and it will be upgraded to a new one but recently it has had a problem.

i launch the boat head out 10-15kms at almost full noise do some fishing crank it up again it starts no problems but when i give it some throttle it bogs down like its over fueling or something does anyone have any idea what it could be.

if i nurse it for a couple of minutes i can slowly get it up to full throttle and it makes the journy home with no problems and i can bring it back to idle and give it full noise and have no probs. it had a new head gasket fitted recently but was doing the problem before hand aswell. i have replaced all fuel lines to the motor but none inside the motor.

cheers

Rod

 


aalfred's picture

Posts: 669

Date Joined: 13/06/09

Hi Rod,I had simmilar

Tue, 2012-01-17 17:38

Hi Rod,

I had simmilar problems with my 2006 Mariner. I found that the Sparkplugs oil up. So I always carried spares with me. But I never could solve the problem.

Cheers Seb

Posts: 877

Date Joined: 03/05/11

+1

Tue, 2012-01-17 17:59

Happened with my 06 Merc. Too much oil getting in to the motor?

roddo's picture

Posts: 486

Date Joined: 16/10/09

is there any way of stopping

Tue, 2012-01-17 18:03

is there any way of stopping it?

 

Posts: 301

Date Joined: 20/12/09

Happen to have had a very

Tue, 2012-01-17 18:12

Happen to have had a very simmilar issue with mine.

Seems to be (in mine hope it helps) that the unit that injected the 2 stroke oil was faulty. It used to inject far more then needed at certain times and would bog down the motor and  then cause the motor to flood. This would then cause me to have to sit there and f with it for about 15 mins before it would start cleanly and run.

Not such a problem when the motor is hot and therefore when she is up and running nicely it would handle the oil.

I removed the oil injection unit and mix at 50 to 1 in the tank (I know it sounds archaic but it works) I have not had a single problem with the motor since and have got a year and a half more then I expected before a repower....Still counting

roddo's picture

Posts: 486

Date Joined: 16/10/09

cheers for the info but mine

Tue, 2012-01-17 18:15

cheers for the info but mine isnt oil injected

i mix mine at 50-1

chris raff's picture

Posts: 3257

Date Joined: 09/02/10

change the plugs

Tue, 2012-01-17 19:06

and strip and clean the carby see if she behaves then ...otherwise a hammer or call a mech and hopefully she does the same when not under load so you can get to the reason...seems to be a common ole 2 stroke ailment

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poida's picture

Posts: 234

Date Joined: 08/08/05

Sounds like it is

Tue, 2012-01-17 20:52

Sounds like it is intermittantly not firing on all cylinders.  When it is bogged down on full throttle pull the ht leads off the spark plugs one by one.  When you remove a plug lead and the motor does not change you have found the problem cylinder.  Other than that i had a mates motor that did that every now and again, never worked it out but a few squirts of petrol down the carby would make it pick up then run fine for the rest of the day.

groper down below's picture

Posts: 109

Date Joined: 19/11/11

could be a carbie prob to try

Tue, 2012-01-17 22:41

could be a carbie prob to try buying some power tune and feeding it straight into the carbie and it might free it up a bit but really u will need to take it in to get the carbie pulled apart and cleaned throughly i had a look at doing mine i got the pics for it but they got about 300 parts so i said fuk it and bought a new motor !!! but the power tune did help it a bit

Posts: 21

Date Joined: 23/09/07

 If you find the problem let

Fri, 2012-01-20 06:26

 If you find the problem let me know mine is the same and drives me mad

Posts: 21

Date Joined: 23/09/07

 I found that if you give it

Fri, 2012-01-20 06:30

 I found that if you give it a heap of revs just after starting it clears itself and should pick up a lot quicker so your not waiting 5min till you can actually get a move on again it's working for me till I find the prob