1980 johnson 85 h.p.

[fernley tim]

I just repowered my boat with a 1980 johnson 85 h.p.. I was able to water test my boat wed. The motor started right up, in neutral I could rev motor over 5000 rpm's. when I put it in gear at full throttle I could only get around 1700 rpm's and 8mph on my gps? the motor has 135# compression on all 4 cylinders and I could not detect a miss when I put it under load. I had a strong/hard fuel bulb. any Ideas? Thanks Tim.

 

[Rudemen]

Re: 1980 johnson 85 h.p.

Any idea how long this motor has been setting up for???

Carbs, jets may need a good cleaning, sounds like the main jets are a little restricted and it wont hurt to make sure the fuel pump is pumping fuel with fuel tank on the ground not in the boat.

 

[BonairII]

Re: 1980 johnson 85 h.p.

How were you able to rev that high in neutral?

Not a good idea to rev anywhere near 5k in neutral....unless you want to turn your good motor into your 'non-running' motor.

 

[fernley tim]

Re: 1980 johnson 85 h.p.

The guy I bought it off had it removed from the boat and had it hanging on a engine hoist with muffs hooked up when I bought it. I have a 20 gallon belly tank on my rig. it idles smooth. under load it just bogs down.

 

[BonairII]

Re: 1980 johnson 85 h.p.

under load it just bogs down.

VERY common problem. ^^^^^^^^^^^

Take apart your carbs and clean every orifice well. Also, check to make sure that your timing is advancing when you throttle up.

 

[fernley tim]

Re: 1980 johnson 85 h.p.

How were you able to rev that high in neutral?

Not a good idea to rev anywhere near 5k in neutral....unless you want to turn your good motor into your 'non-running' motor.

It was at 5000 for a split second was checking the the throttle throw. It was smooth from low rpm's to hi r's

 

[Rudemen]

Re: 1980 johnson 85 h.p.

The guy I bought it off had it removed from the boat and had it hanging on a engine hoist with muffs hooked up when I bought it. I have a 20 gallon belly tank on my rig. it idles smooth. under load it just bogs down.

Yea, sounds like you need to clean the carbs real well, first I would start with checking the fuel pump and make sure it pumps fuel well with a fuel tank on the ground, these fuel pumps should be able to suck fuel from the tank @ 3 to 4ft above fuel tank, if it doesn't, replace it. If it pumps real well move on to cleaning both carbs.

 

[BonairII]

Re: 1980 johnson 85 h.p.

I believe most motors have a safety device that doesn't allow motor to throttle up til it's in gear. Maybe yours is missing or broken.

 

[fernley tim]

Re: 1980 johnson 85 h.p.

I believe most motors have a safety device that doesn't allow motor to throttle up til it's in gear. Maybe yours is missing or broken.

when mine is in neutral I can pull my throttle control to the left and get full throttle control my kicker control has the same throttle control. its a 1993 cc 20' greggor.

 

[Rudemen]

Re: 1980 johnson 85 h.p.

I also wanted to add;

I wouldn't spool that engine up to 5000 rpm like that, if one of the two carbs is performing properly and the other one isn't, there is a good chance of smoking one or two of the cylinders the faulty carb is feeding and you end up with a Parts motor.

Secondly, pulling the spark plugs and taking note of each plug in relation to the cylinder they came out of and it's condition (White, Black, Dark brown, Wet, or Dry) can tell you/us a lot about how your motor is performing.

 

[Rudemen]

Re: 1980 johnson 85 h.p.

I also wanted to add;

I wouldn't spool that engine up to 5000 rpm like that, if one of the two carbs is performing properly and the other one isn't, there is a good chance of smoking one or two of the cylinders the faulty carb is feeding and you end up with a Parts motor.

Secondly, pulling the spark plugs and taking note of each plug in relation to the cylinder they came out of and it's condition (White, Black, Dark brown, Wet, or Dry) can tell you/us a lot about how your motor is performing.

 

[emdsapmgr]

Re: 1980 johnson 85 h.p.

Possible the engine is only running on 3 cyls. These engines will seem to run fine on 2 or 3 cyl, till you put the boat in the water. Once the prop is 2' under water and the engine is in gear, you need all 4 cyls firing. Run the engine on the trailer with the muffs. With a pair of insulated pliers, pull each of the spark plugs wires off the plugs one at a time. Note the rpms. When each wire is pulled off, the rpm's should drop. If you pull one of them off and nothing happens, it is not firing. An inductive timing light on the plugwire will tell you a lot about the spark. The flashes in the gun will show misfires, no fires, weak firing.

 

[outboards115]

Re: 1980 johnson 85 h.p.

See if the fuel lines are blocked also, are any of the wires corroded.

 

[outboards115]

Re: 1980 johnson 85 h.p.

Also

you might want to check the diafram and gaskets in the fuel pump, and chek if it is firing on all cylinders.
when you cheked the compression was there any big differences in each cylinder?, if there was
take the heads off and see if a piston hasn't chewed up a ring.