Johnson 150 faststrike overheating? maybe not. update with *pics* Help!

[3car]

I'm ready to shoot this motor.

Ok, a few of you may have read my thread about my 150 quickly overheating at start-up. http://forums.iboats.com/showthread.php?t=222117
Or so I thought. I have a constant alarm tone about 30 seconds after start-up, and the heads felt hot to the touch. No temp gauge, no water pressure gauge, but a strong tell-tale and the impeller and stats are recent.
Today I borrowed a thermal heat gun from a buddy, and after about 20 minutes of ideling with the alarm going, the head temps near the spark plugs and temp sensors were between 129 and 140 degrees. Not exactly overheating.

I disconnected the temp senders in each head, and the shift interupt switch, but the alarm continued. What gives?

 

[iwombat]

Re: Johnson 150 faststrike overheating? maybe not. update with *pics* Help!

Your sender wire is probably shorting to ground someplace between the motor and the console.

 

[3car]

Re: Johnson 150 faststrike overheating? maybe not. update with *pics* Help!

That sounds very logical. I will look into that tomorrow, thanks.

 

[Dhadley]

Re: Johnson 150 faststrike overheating? maybe not. update with *pics* Help!

Are you using the oil injection?

 

[3car]

Re: Johnson 150 faststrike overheating? maybe not. update with *pics* Help!

Are you using the oil injection?

as bad as this may sound, im not really sure. I think the guy I bought it from said it was blocked off somehow, and he was premixing. I havent added any fuel to the boat yet. This motor is a lot different than any I have worked on before. I ordered a manual for it, but it hasen't made it yet.
How do people usually disconnect the oil injection on these motors?

 

[3car]

Re: Johnson 150 faststrike overheating? maybe not. update with *pics* Help!

Are you using the oil injection?

does the oil injection alarm give a constant tone?

 

[angus63]

Re: Johnson 150 faststrike overheating? maybe not. update with *pics* Help!

Constant alarm is overheat or fuel starvation. Rapid beeping is no oil. intermittent beeps (40 seconds) is low oil. If you disconnected both temp sensors and still had a constsnt alarm after 30 seconds run time, I would focus on the fuel sensor (vacuum switch) to eliminate that as faulty. Your head temps appear to be normal (appx 140 F). Fuel sensor is just below the white plastic fuel screen housing (two pin amphenol connector). Another possible reason is a faulty horn. Does it beep when key is initially turned on? Just for giggles, try wiggling the ignition key after tone starts constant tone and see if it interrupts the tone.
Good luck

 

[3car]

Re: Johnson 150 faststrike overheating? maybe not. update with *pics* Help!

Fuel starvation, maybe you're onto something there. The motor will idle fine either on the muffs or in a barrel, but in a barrel with backpressure on the exhaust, it wont rev and it stalls. it starts back effortlessly and idles fine.

Maybe i should start with the basics such as replacing the water seperator filter. I planned on cleaning the carbs today, but I feel terrible.

 

[CharlieB]

Re: Johnson 150 faststrike overheating? maybe not. update with *pics* Help!

Also re-route the port bank temp sensor wire (tan w/blu trace) out right and up, use a zip tie around the wire and the convienent hole in the top right of the bock to hold the temp wire well away from the spark plug wires. left side looks good.

Once in a while I find an ignition soo sensitive to RF off the plug wires that it really makes a difference how that right side wire is routed.

Thanks to the folks at CDI Electronics for teaching me this!

 

[3car]

Re: Johnson 150 faststrike overheating? maybe not. update with *pics* Help!

Also re-route the port bank temp sensor wire (tan w/blu trace) out right and up, use a zip tie around the wire and the convienent hole in the top right of the bock to hold the temp wire well away from the spark plug wires. left side looks good.

Once in a while I find an ignition soo sensitive to RF off the plug wires that it really makes a difference how that right side wire is routed.

Thanks to the folks at CDI Electronics for teaching me this!

Thanks, I'll re-route that as well.