Johnson temp alarm

[virii01]

Took the boat out for the first time this year. Started fine then idled great for about 5 minutes. Then a high pitched alarm went off which I assume is the overheat alarm. My water pump stream was fine and I didnt have any issues last time out last year.
Motor would not restart till I let it sit for a few minutes. When I turned the key I just got the same high pitched alarm.
Thoughts? Im at the lake so I cant get parts till I get home.

 

[virii01]

Re: Johnson temp alarm

Forgot to mention it is an 82 115hp.

 

[virii01]

Re: Johnson temp alarm

Any ideas? Thermostat?

 

[cdn-pk]

Re: Johnson temp alarm

My 86 120 thermostats have an air bleed hole in the side of the gasket. i've heard if those get blocked then you can get an air lock. i'd pull off the thermostats and give'em an inspection.

other thoughts: was water pump stream hot?

 

[Mark42]

Re: Johnson temp alarm

My 86 120 thermostats have an air bleed hole in the side of the gasket. i've heard if those get blocked then you can get an air lock. i'd pull off the thermostats and give'em an inspection.

other thoughts: was water pump stream hot?

I second cdn-pk's assessment. Just wanted to add that the cylinders should be able to touched for a few seconds before it gets too uncomfortable to touch. That would indicate normal operating temps. If its too hot to touch, it probably is overheating. It the T-stats are good, look to the water pump for a worn/failing impeller.

The other possibility is a bad temp sensor, or a break/pinch/abrasion of the temp sensor circuit wiring (tan color) that is grounding the circuit causing the horn to sound.

 

[lkrasner]

Re: Johnson temp alarm

i have a '95 115 that had this problem for a while. It also went in to SLOW mode because of it constantly turned out to simply be a bad temp sensor. I replaced it and it has worked fine since

 

[virii01]

Re: Johnson temp alarm

Thanks guys. I'll put it in the tank and try the suggestions tonight. I heard replacing the thermostat is a PITA, true?

 

[Mark42]

Re: Johnson temp alarm

The covers are usually corroded on, and the use of 4200 or 5200 to seal them does not help. Use a big socket, not a small one that fits the middle to reduce the risk of breaking the cover. Use new O ring and seal with Boat Life, not 4200, if you want it to seal and come apart later easy.

 

[emoney]

Re: Johnson temp alarm

Part of the PITA, is getting your hands and tools in there to hold everthing in place when putting it back together. Check your current tstats and verify they are bad before buying the new kit, though. There's other issues that could affect it overheating, i.e. bad water pump/impellar, diverter hoses being off, etc. Do you have a temp guage to verify the overheat? The temp sensors can go bad, as mentioned, so with a guage, you'll at least be able to verify that. Just because she shows water out the telltale doesn't confirm the pump is working properly. Do you have water coming out the exhaust holes?

 

[pieman22]

Re: Johnson temp alarm

I had the same problem with my V4 115 bubble back model. No picnic replacing the Tstat but I think i figured out a way thats less stressfull if you have the same model. I drilled 3 3/4"holes in lower pan in line with the Tstat bolts. It allows you to easily use an extension to get the bolts right out. After you re-assemble the Tsta with a new kit you can use the extension to assist in pushing the center bolt to compress the springs as you attempt to catch the threads. When the center bolt catches the threads its all down hill from there. Make sure you clean the bolt holes and grease the bolt to make finding a thread much easier.

 

[Caseyuconn]

Re: Johnson temp alarm

I was looking a the diagrams for your motor and I have a couple things to offer from recently going through this.

1. Your telltale is prior to the t-stats so a strong stream at the tell is a sign the water pump is functioning properly but does not mean the rest of the cooling system is operational.

2. I just changed my T-stats on 1995 88 SPL which has the same set up as yours. Not really a big deal at all. You will have to take off the lower plastic cover of the motor.

3. In diagnosing the issue get a infrared thermometer and run the motor in a tank. Take readings on the cylider heads. Your T-stats are rated to open at 143 degrees. The heads shouldn't get hotter than high 150's/ low 160 idling in a tank. Running at some speed in open water actually cools the motor more because the poppet valve will open, flooding the motor with more water.

If you change your t-stats and it still overheats it is probably clogged water jackets or misplaced water deflectors. I would start with running it, use a thermometer to see if it is actually getting hot then change the t-stats.

Just my 2 cents

 

[virii01]

Re: Johnson temp alarm

3. In diagnosing the issue get a infrared thermometer and run the motor in a tank. Take readings on the cylider heads. Your T-stats are rated to open at 143 degrees. The heads shouldn't get hotter than high 150's/ low 160 idling in a tank. Running at some speed in open water actually cools the motor more because the poppet valve will open, flooding the motor with more water.

Great suggestion. Lowes just happens to have an entry level IR thermometer on sale for $10.

 

[Dinky775]

Re: Johnson temp alarm

I have an 89 v4 johnson 85hp, had a steady alarm, pump was good, pee stream was great, took out both tstats and placed them in boiling water, 1 opened and the other was junk! i thank the fellas who replied on this post! you helped me out!