1981 Johnson 75hp won't accellerate AT ALL!

[BonairII]

The motor is pretty new to me. When I first picked up the motor...spark was weak on all cyls, so I just replaced all 3 coils/spark plugs. Compression was 120/120/100. (Not great numbers, I know). I decarbed the snot out of it the other day, but didn't do another compression check to see if the bottom cyl compression improved.

Carbs were removed, cleaned, and all fuel lines involved with the carbs were replaced.

The motor starts quickly/easily on muffs(classic story). When I put it in the water, it starts easily....but when I put it in gear and push the throttle forward....NOTHING. It doesn't bog or even seem to do much of anything. The first time I ran it on the water, it would go into gear and only run at 2k rpm and putt along.

Took the boat out yesterday(post decarbing) and had a heck of a time getting it to stay running when I put it into gear. Stalled it about a dozen times until it finally would stay running to "putt" us back to shore.

I bumped the choke to see if the motor would perk up, but it bogged when choke was activated. I pulled the cowling and pushed throttle forward ....and viewed that the carbs are opening and timer base seems to be rotating correctly.

Anyone have any idea what's going on with this motor?

 

[Will Bark]

Head gasket?

 

[BonairII]

Head gasket?

What makes you think "bad head gasket"? I'm wondering(hoping) that maybe head gasket may be causing the low compression in the bottom cylinder...but I don't think that has anything to do with the fact that when the boat is at wake speed.... I push the throttle further forward nothing happens(no bogging, sputtering, etc etc).

The other day the motor pushed the boat at "wake speed"(2k rpm)...but when the throttle was pushed forward there was NO CHANGE at the motor(no bogging, etc)...it was like I hadn't even touched the throttle. Day 2(post decarb) it seems to be running worse than before(stalling) when put into gear.

When I get a chance, I'll re-check compression and do another spark check...and then link-n-sync. I'll pull the airbox cover also and make sure that the carb linkages are correct and functioning.

 

[ronward]

Is the throttle cable actually moving the throttle arm? I'm wondering if maybe the cable could be slipping inside your control box.

 

[BonairII]

Update: Post decarb numbers. 120/120/110

I now have no spark on the middle and bottom cylinders. I could've sworn I had spark(albeit weak) on all 3 cyls when I first got the motor, but unfortunately I'm not sure. All 3 coil are brand new.

Is this likely a powerpack problem? I have a DVA adapter but have ZERO idea how to use it to test the PP.

 

[BonairII]

Update: I replaced the powerpack.....and just my luck.....still no spark on middle and bottom cyls.

Anyone have an idea on what the heck could be causing 2 cyls NOT to fire? Coils, spark plugs/wires and powerpack are new.

 

[Bosunsmate]

Test timing base and stator with your DVA

 

[BonairII]

Test timing base and stator with your DVA

How do I do that? I have a multimeter and dva adapter, but have no idea what to set the MM to and have no idea where to touch the probes etc to test it.

 

[Bosunsmate]

Its provided in here, just look your motor up and it will tell you where to collect the meter leads too and also any other instructions
http://issuu.com/cdielectronics/docs/troubleshootingguide

 

[BonairII]

Changed out stator and timer base(from a parts motor). I now have spark on al 3 cyls, Problem is that it won't start now. Any ideas? Have an odd feeling that middle and bottom cylinder wires are reversed. What are symptoms of crossed wires?

 

[EZSteury]

When Mine did what You described it turned out to be the carburetor, more specifically the needle was worn too far but after I rebuild the carb it all went away.

 

[racerone]

Orange and blue on the top coil ? -------------Orange and green on the bottom coil ??