Johnson 150hp dies at speed

[stricksteve4]

I have a 1985 Johnson J150TCOH. I have had some work done on it recently, replacing the impeller,the thermostats,the priming bulb and a general checkup. Compression is good per spec. It was bought this summer after only running it on muffs. When I get it up to speed,(4500rpm) it will run well for a few minutes and then just die, like it ran out of fuel. Rpm goes down to zero in about 2-3 seconds. Does not spit or pop, it just dies. Does this engine have some sort of oiling sensor that will cut the engine if it does not get enough oil from the oil injection?? Also after the recent service , it is extremely cold blooded and will not even idle under load. until very warm. It will start easily, and after warming for a few minutes if shifted into forward, it will stall out. It is a struggle to keep it going until it is warmed up totally. The shutting off at speed is my main concern!! Please if anyone has seen this problem before, help!! Could it be the fuel/oil pump??

 

[dodgeboy1979]

Re: Johnson 150hp dies at speed

with the gereral checkup were the plugs changed, fuel filter etc... have all the fuel lines in the motor been inspected, the carb may also need a good cleaning or you are not getting a proper spark at the plugs. All little things to give a look at as i had a similar problem with my 70hp this year and it was these little things that gave me grief.

 

[boobie]

Re: Johnson 150hp dies at speed

Sounds like you're loseing your spark.

 

[danoutbard]

Re: Johnson 150hp dies at speed

Yeap time to check spark,do you have an air gap tester?

 

[stricksteve4]

Re: Johnson 150hp dies at speed

with the gereral checkup were the plugs changed, fuel filter etc... have all the fuel lines in the motor been inspected, the carb may also need a good cleaning or you are not getting a proper spark at the plugs. All little things to give a look at as i had a similar problem with my 70hp this year and it was these little things that gave me grief.

The plugs are new and as is the fuel filter. The new primer bulb was tested and fuel flows easily from the tank to the motor. I do not know if all the fuel lines were individually checked. It looks like there are individual coils for each plug or set of plugs. Is there one central item that feeds all the coils? Since it is oil injected, does it have an oil sensor for shutdown if no or little oil is flowing?? Are these motors generally cold blooded when starting or was something possibly misadjusted when it was reassembled after replacing the impeller??

 

[emdsapmgr]

Re: Johnson 150hp dies at speed

That engine will not shut down for oiling issues. However, it should sound the warning horn inside the control box-based on what type of oiling problem you have. The oil warnings are different from an overheat or or (high) fuel vacuum sensor warnings. Possible you are losing spark. That engine will seemingly run just fine on the garden hose with only 3 or 4 cyls firing. When you put the boat in the lake, you need all 6 plugs firing. Next time you go boating and the engine quits, check all 6 plugwires for spark. Remove the cowling and crank the engine over. An inductive timing light will show the quality of spark on each wire.

 

[stricksteve4]

Re: Johnson 150hp dies at speed

That engine will not shut down for oiling issues. However, it should sound the warning horn inside the control box-based on what type of oiling problem you have. The oil warnings are different from an overheat or or (high) fuel vacuum sensor warnings. Possible you are losing spark. That engine will seemingly run just fine on the garden hose with only 3 or 4 cyls firing. When you put the boat in the lake, you need all 6 plugs firing. Next time you go boating and the engine quits, check all 6 plugwires for spark. Remove the cowling and crank the engine over. An inductive timing light will show the quality of spark on each wire.

I guess the spark and coil check will have to wait until spring. I have not checked any of the coils or anything feeding them. I will check all this out in the spring,(the boat has been winterized and is in my garage for the snow season) .
Thank you all for your help, I will go through the ignition system in the spring!!