70hp bogging down

[Dennischaves]

I have a 1984 70hp it starts and idles great yesterday going out from the ramp it ran fine through the no wake zone
when I hammered the throttle it just bogged down
on the way back to the ramp it struggled just to troll
I had this happen last time out so I cleaned the carbs the primer bulb was hard and I tried pumping it with no change
and fuel lines are new spark and compression is good
the local mechanic said the carbs non adjustable on those motors and that I need a set of adjustable carbs

 

[racerone]

Everybody seems to jump on the carburetors first in search of the magical fix.----What other trouble shooting are you prepared to do ??----Or how has this motor been able to exist for 36 years with non adjustable carburetors ???-----When you had the carburetors apart for cleaning did you remove the high speed jets ( orifice plugs ) found INSIDE the carburetor bowl ?-----They are about 5/8" long with a calibrated hole.

 

[Lakemichfish]

I’m having the same problem with my 1990 Johnson 70 hp. The water pressure jumps between 0-20. I’m making the change to the coolant system pr SB #2276 but I don’t think it’s the cause in this case. Sometimes the overheat alarm sounds when this happens, sometimes not.

 

[Dennischaves]

I've rebuilt the carbs ever year for the last 8 years as a precaution so I know they are super clean and done properly
it has good spark and compression was good
it fires all all 3cyl

 

[racerone]

What are the actual compression numbers ??-----Perhaps throttle plates are opening too early.----Carburetors do not need to be cleaned / rebuilt every year.----Just run the fuel out of them and they stay clean..----Other trouble shooting needs to be done !!

 

[Dennischaves]

compression test was 105 107 and 110
spark test was good too 7/16 jump

 

[racerone]

On my tester that motor will show 140 PSI on a good one.------So pull the cylinder head off.------A new head gasket is cheap if there is nothing wrong there !!!----Cheaper than buying coils / stators / timers bases and powerpacks in desperation !

 

[Dennischaves]

went down to the water this morning to try to run it again
if I push the key in to activate the primer the motor accelerates

 

[Dennischaves]

im going to buy a better compression gauge and try the compression test again

 

[racerone]

When you push the key in the fuel primer valve opens.-----It then sprays fuel into the engine.-----This fuel bypasses the carburetor metering circuits.-------This tells me that perhaps something was missed / overlooked during carburetor work.------Be an easy fix here I think !

 

[Dennischaves]

I'm going to take them apart again just to double check
I'm sure nothing was missed

 

[racerone]

??----But your motor is not running correctly !!----Or bring your motor over .---I think it is easy fix !

 

[Dennischaves]

it did it before the carb rebuild also

 

[racerone]

It is becoming clear to me over many years.----Folks are not good at trouble shooting simple outboard motors ---Sorry to be so blunt.