1976 Johnson 70 HP no power

[Johnmari]

I had low compression 90-100 and I have replaced crankcase gasket and now have 110-120 compression on each cylinder but I am not sure what the torque settings are for this. And I still do not have any power on the water runs good on water hose but as soon as I put it in gear on water it dies. I have cleaned the carburetors and noticed that my jets are 30. I have read some things on here about some modifications but not sure what to do I know from what I have read they are supposed to be a 32. Is there any way I can get a copy of the modification that is supposed to be done. I am at a loss with this motor. It also has a new strater and fuel pump.

 

[F_R]

IDLE jets are #30. HIGH SPEED jets are supposed to be part number 321407, #54. Did you inspect those?

#31, 32 and 32 idle jets were offered to be used as necessary to correct poor idle (usually lean sneezing)

EDIT: You replaced the crankcase gasket?? Do you mean the head gasket? Head gasket torque is 168-192 INCH pounds. Retorque to 192-216 after motor test and cool-down.

 

[Johnmari]

The gasket that is a o-ring type where the head and crank case attach. Which jets are the ideler jets the ones on top under the float or on bottom behind the bowl. I heard also that the jet shaft going through the middle the holes are supposed to be a #54 drill bit. Thanks for helping.

 

[F_R]

The high speed jets are the ones in the carburetor bowls. The numbers are the orifice diameter in thousandths.

 

[fireman57]

do a search for service bulletin 1144

 

[Johnmari]

That is the service bulletin 1144 I am looking for I can't find the actual paper work that shows it only word of mouth

 

[Johnmari]

1976 Johnson 70 hp no power in gear

I have done the update on the carburetors, replaced strater, crankcase gasket, have good compression on all cylinders 115-120 but when I go to put it in gear it wants to die will run good just at idle. I have been told that they usually do not jump timing I AM VERY FRUSTRATED PLEASE HELP ME

 

[racerone]

The way for timing to go out of adjustment is by a novice trying to adjust the timing !!!----Also if flywheel nut is not properly torqued the key will shear and that knocks the timing out.---Start with a compression test first and foremost.

 

[Johnmari]

I did not try and adjust timing and the compression is good on all cylinders

 

[Johnmari]

Have done the update and still no power????

 

[racerone]

Check for spark on all 3 leads.----See if it can jump a gap of 7/16"

 

[Tim Frank]

Numbered drill bits numbers have no relationship to HS orifice numbers. The "scales' are actually opposite. Larger drill number is smaller size.
By coincidence the sizes are close at #54, but the drill is still too big by a thou.

An OEM manual would be a great purchase.

Can you provide some relevant history....how long have you had the motor....has it ever run properly for you...how did you clean the carbs...and any other diagnostics?

 

[GA_Boater]

John - You had two topics going for the same problem and you are getting replies in both. The two have been merged to lessen confusion.

 

[Johnmari]

Tim I bought the boat and motor about 2 months ago but before that it sat up for about 8-10 years. It has never ran on the water only on water hose and does good there but under a load on water no power it wants to die. I have changed strater, plugs, had one bad coil changed it, crank case gasket was leaking changed it and it doesn't have a leak now before I changed it only had about 90 compression now have between 115-120. I took carburetors all the way apart it had 30 jets I made them bigger to a 32 checked all ports and floats all good. I have cleaned them 3 times already keep thinking I'm missing something. The fuel pump seems to be putting out enough fuel on the test. Put new primer bulbs on and all new fuel line. PLEASE HELP I JUST WANT TO GO FISHING

 

[racerone]

Sounds like the high speed jets ( orifice ) may be plugged.-------They are found in the very bottom of the carburetor bowl.-------Best way to clean them is to remove them.----Were they removed ??

 

[Johnmari]

Is that the ones behind the drain plug in the bowl if so no they was not removed and cleaned.. Are they supposed to be a 32?

 

[eavega]

Johnmari, did you ever get the TSB you were looking for? The issue with the 1976 70 HP was a mid-range hesitation when rolling throttle. My motor exhibited this behavior; it would idle all day long, and when you got it to WOT it would run all day long. Problem was that you had to baby the throttle from idle through the throttle range, because there was a dead spot in the mid-range. The change involved changing out to larger idle jets as well as drilling out some of the ports and the mixing chamber opening.
Have you verified carburetor synchronization and timing?

Rgds
Eric

 

[eavega]

Johnmari, did you ever get the TSB you were looking for? The issue with the 1976 70 HP was a mid-range hesitation when rolling throttle. My motor exhibited this behavior; it would idle all day long, and when you got it to WOT it would run all day long. Problem was that you had to baby the throttle from idle through the throttle range, because there was a dead spot in the mid-range. The change involved changing out to larger idle jets as well as drilling out some of the ports and the mixing chamber opening.
Have you verified carburetor synchronization and timing?

Rgds
Eric

 

[Johnmari]

Here is the link I have been going off of do you have have any info on this?

 

[Johnmari]

No Title

# 35 says it's a plug?