Help required - 70hp Johnson 2000 model

[Andos2009]

Hi there, I have a re occuring problem with a 2000 70hp Johnson. Three mechanics have looked at the motor and have been unable to diagnose the problem.

Here it is. The motor will start and run beautifully from a cold start. I will drive the boat for 25 mins and then turn it off. I will leave the motor off for 15 - 25 mins and then turn the key. The motor will idle in neutral and then drop out. It can't keep the revs and when I try to get the motor into gear it will also drop out unless I can get it over 1500 - 1700rpm.

Here are the parts that have been replaced by mechanics who have thought they diagnosed the problem and stuffed up!

1. Powerpack
2. trigger and stater
3. bottom cylinder solinode

Can anyone let me know if they have experienced a similar problem?

The current mechanic has not given up and has (in his opinion) narrowed it down to an electrical problem and is going to test a new throttle box with my motor running direct with no other electrics. Does this sound right?

FYI - compression on all cyclinders is 135psi. The motor is in immaculate condition apart from this issue. To get the motor into gear on a WARM START ONLY is to tilt the motor to reduce the load back pressure and the motor will shack and sound sick before taking off over 2000rpm where the boat will then become ok again. Note the issues are only in neutral and low revs ONLY.

As you can probably tell I am extremelly frustrated and ready to trade this motor for a new 4 stroke if the issue cannot resolved in the very near future.

Thanks in advance

Andy

 

[Faztbullet]

Re: Help required - 70hp Johnson 2000 model

Does the engine smoke on restarting? Possible causes for your problem are:
1) Electrical problem (timer base or rectifier problem)
2) Carb flooding a cylinder
3) Vapor lock
4) Fuel restriction(kinked line,anti siphon valve,bad primer bulb)
My vote goes to #1

 

[JB]

Re: Help required - 70hp Johnson 2000 model

"Here are the parts that have been replaced by mechanics who have thought they diagnosed the problem and stuffed up!

1. Powerpack
2. trigger and stater
3. bottom cylinder solinode"

Get yourself different techs.

Changing parts is the most used, most expensive and least effective troubleshooting method known to man.

 

[ctf58]

Re: Help required - 70hp Johnson 2000 model

I have a 1996 70hp that is doing the exact same thing. Starts easy and runs great on initial start-up. on restarts it will start and idle rough, drop it in gear and it will die. restart put it in neutral, rev it up 3-4 times, return to idle and drop it in and go to WOT. If this works it works the engine purrs like a kitten. I can drop off of plane and idle then take off again fine. I am going to replace the primer bulb because it is getting old. Seems like maybe mine is losing "prime". That is only a guess and when I replace the fuel line and bulb I will know if it was the problem.

Bottom line is that you are not alone and the problem is a real pain because you never feel confident that you are going to get moving again.