Diagnosing Overheat warning, 1990 Johnson 60

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Author Topic:   Diagnosing Overheat warning, 1990 Johnson 60

69boo307 posted 04-19-2010 01:13 PM ET (US)
I'm looking for some advice for diagnosing an intermittent overheat warning with my outboard. My last 2 outings the warning has sounded, usually after at least a couple hours of running time at various speeds. In the most recent case I had been out all day running the engine at speeds from idle to 5000rpm and on the way back to the dock the horn sounded.
The rev limiter kicks in and won't allow it to go over 2500 at that point, which is what it is supposed to do for an overheat condition. After a few minutes I can usually turn the ignition off and back on, and everything will work fine again, until it goes off again.
Here's what I've done/checked:
-New impeller about a month ago (3 or 4 boat outings ago
-Pee stream looks OK visually, it never stops or looks 'weak'.
-When horn sounds, I inspected the engine externally and by touch, it didn't feel overly hot either on the cover or directly touching the engine with the cover off. I could touch it with my hands.
-Water intake screens are clear, no visible obstruction.
-I plan on replacing the 20 year old Temperature Switch. For $25, it is easy to rule that out.

69boo307 posted 04-19-2010 01:15 PM ET (US)
Oh one other key point, I never had this problem BEFORE replacing the impeller and impeller key. Makes me wonder if something is wrong with the new impeller. Then again, perhaps it is just coincidence? I did have one all day outing immediately after the new impeller installation, with no issues.
jimh posted 04-19-2010 01:56 PM ET (US)
You need a water pressure gauge to know if the water pump is working properly.
tom976 posted 04-19-2010 02:04 PM ET (US)
The other option is to use an infrared thermometer. You can check each cylinder and see if there are any hot ones.
Did you ever change out the thermostats? Most people dont change them for YEARS. They can look nasty (and work even worse) when they havent been changed in a number of years and used in salt water.
DillonBW posted 04-19-2010 02:12 PM ET (US)
I have the same [over-heat warning alarm] with my motor, same HP, same vintage, new impeller, new thermostat, and new sensor, and it still [gives a over-heat warning alarm] completely at random times. [The motor] would run for five minutes and [the over-hear warning alarm would] go off, then the next outing, run for two or three hours before sounding off. [The alarm] has driven me and my local mechanic insane, he cannot duplicate it when he has [the boat] at his shop! If you find anything new please post it here. I am getting ready to rip my motor apart again or trade it for an E-TEC. Thanks to Yiddil and his postings about his new motor.
pcrussell50 posted 04-19-2010 02:31 PM ET (US)
Infrared thermometer, yes. I got a Craftsman one for $69 during a Craftsman club sale, while it was also on sale in its own right. The cheaper, and just as good, solution is to get a thermomelt crayon. It's special compound of wax that melts at and above a certain temperature. You can buy several for different temperatures. Most marine mechanics have them in their parts department, or you can find them online.
-Peter
69boo307 posted 04-19-2010 02:42 PM ET (US)
There is a section in the service manual describing using the thermomelt stuff. It talks about doing tests with a test wheel in a tank though. I would have to attempt the same tests on the water. I may do it nonetheless.
69boo307 posted 04-19-2010 02:45 PM ET (US)
Tom976, the thermostat is a good idea, I hadn't thought of that on the boat engine. I suppose a sticking thermostat could cause problems.
tedious posted 04-19-2010 04:11 PM ET (US)
TSB 2221 for the 60 and 70s changed out the temperature switch for a new one with a higher "trigger" temperature. If your motor does not have the new switch, it's quite likely that's the problem. I was suffering the same symptoms last year and have just ordered the new switch.
Tim

Info:
SB 2221 Temp sensor new sensor pn 584166, tan/blue stripe wire replaces earlier part with plain, brown wire.
tedious posted 04-19-2010 04:18 PM ET (US)
Another potential contributor to the problem is covered by SB 2276R1 (relocate tattle tale nipple to top of block). Without this change, if you run through aerated water you can get an air pocket in the top of the block which can cause the top cylinder (where the temp sensor is located) to overheat.
I'm guessing the new switch is most of the problem, but wanted to make you aware of this as well.
Tim
69boo307 posted 04-19-2010 06:51 PM ET (US)
Thanks Tedius! I took the the thermostat out when I got home and opened the housing. It wasn't corroded, but I did find a small piece of silicon gasket sealer in the housing, same as I used on the water pump housing. I'm wondering if it couldn't have prevented the little mechanism from opening fully?
jimh posted 04-19-2010 11:09 PM ET (US)
You need to get a water pressure gauge so you can see if the new water pump impeller installation was done properly and produces the proper water pressure. All this speculation about the over-heat alarm being false is only reasonable once you prove the water pump is putting out the proper pressure.
tedious posted 04-20-2010 07:38 AM ET (US)
In 69boo's case, Jim is quite right - since the problem seemed to come on very suddenly, coincident with an impeller change, it would make sense to verify that water flow is working as it should. It's also certainly possible that the piece of silicone goop was interfering with the flow in some way.
However, in 69boo's case in the longer term and particularly in Dillon's case, if makes sense to change out to the newer temperature switch. From another forum the old switch appears to be a problem mostly when the water temperature is over 70, or running with a heavy load at mid-throttle.
Dillon, this might be responsible for your apparently random triggering of S.L.O.W. mode. You mentioned that you did change the switch, but did they install the new version with the blue/brown wire or just a newer original, with the plain, brown wire?
It would also be interesting to know if the telltale hose routing is correct on both these motors. If the telltale hose comes out of the side of the exhaust cover, the SB has not been performed.
Tim
69boo307 posted 04-20-2010 07:56 AM ET (US)
The fitting for my 'pee hole' is on the lower side of the cover, not the top. Is this a hard thing to change? I'm assuming you would plug the old hole and drill/tap a new one? Do you know if I can find the service bulletin online anywhere?
69boo307 posted 04-20-2010 08:02 AM ET (US)
Found a good thread on the topic with a scan of the SB:
http://forums.iboats.com/showthread.php?t=222677&highlight=pee+hole+tell+tale
tedious posted 04-20-2010 08:14 AM ET (US)
Yep, that's where I got a lot of my info. I have not found an actual online TSB, but there are a lot of good posts at that forum.
I did the telltale changeover myself and got lucky - my motor had a new powerhead installed by the previous owner and the new block already had the upper hole drilled, so I just had to swap the telltale outlet with a plug rather than drilling and tapping. Even so, the drilling and tapping seemed fairly straightforward - the location is very accessible.
Tim
69boo307 posted 04-20-2010 08:32 AM ET (US)
Just an 'aside' comment, keeping this old boat engine working right has turned out to be very much like my hotrodding experiences with old cars.
You run it for one weekend, then spend the next 2 weeks working on it :).
tedious posted 04-21-2010 02:38 PM ET (US)
I know what you mean! We got some good use out of our 70 last summer, but I don't have a ton of confidence in it. I had unpredictable S.L.O.W mode from time to time, two separate fuel leaks, and the idle was never great, mostly pretty bad - really made docking an adventure.
I hope that with the idle orifice changes I made, the new prop, and the replacement temperature switch and new telltale routing, things are a lot better this year.
Tim

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Author	Topic: Diagnosing Overheat warning, 1990 Johnson 60
69boo307	posted 04-19-2010 01:13 PM ET (US) I'm looking for some advice for diagnosing an intermittent overheat warning with my outboard. My last 2 outings the warning has sounded, usually after at least a couple hours of running time at various speeds. In the most recent case I had been out all day running the engine at speeds from idle to 5000rpm and on the way back to the dock the horn sounded. The rev limiter kicks in and won't allow it to go over 2500 at that point, which is what it is supposed to do for an overheat condition. After a few minutes I can usually turn the ignition off and back on, and everything will work fine again, until it goes off again. Here's what I've done/checked: -New impeller about a month ago (3 or 4 boat outings ago -Pee stream looks OK visually, it never stops or looks 'weak'. -When horn sounds, I inspected the engine externally and by touch, it didn't feel overly hot either on the cover or directly touching the engine with the cover off. I could touch it with my hands. -Water intake screens are clear, no visible obstruction. -I plan on replacing the 20 year old Temperature Switch. For $25, it is easy to rule that out.
69boo307	posted 04-19-2010 01:15 PM ET (US) Oh one other key point, I never had this problem BEFORE replacing the impeller and impeller key. Makes me wonder if something is wrong with the new impeller. Then again, perhaps it is just coincidence? I did have one all day outing immediately after the new impeller installation, with no issues.
jimh	posted 04-19-2010 01:56 PM ET (US) You need a water pressure gauge to know if the water pump is working properly.
tom976	posted 04-19-2010 02:04 PM ET (US) The other option is to use an infrared thermometer. You can check each cylinder and see if there are any hot ones. Did you ever change out the thermostats? Most people dont change them for YEARS. They can look nasty (and work even worse) when they havent been changed in a number of years and used in salt water.
DillonBW	posted 04-19-2010 02:12 PM ET (US) I have the same [over-heat warning alarm] with my motor, same HP, same vintage, new impeller, new thermostat, and new sensor, and it still [gives a over-heat warning alarm] completely at random times. [The motor] would run for five minutes and [the over-hear warning alarm would] go off, then the next outing, run for two or three hours before sounding off. [The alarm] has driven me and my local mechanic insane, he cannot duplicate it when he has [the boat] at his shop! If you find anything new please post it here. I am getting ready to rip my motor apart again or trade it for an E-TEC. Thanks to Yiddil and his postings about his new motor.
pcrussell50	posted 04-19-2010 02:31 PM ET (US) Infrared thermometer, yes. I got a Craftsman one for $69 during a Craftsman club sale, while it was also on sale in its own right. The cheaper, and just as good, solution is to get a thermomelt crayon. It's special compound of wax that melts at and above a certain temperature. You can buy several for different temperatures. Most marine mechanics have them in their parts department, or you can find them online. -Peter
69boo307	posted 04-19-2010 02:42 PM ET (US) There is a section in the service manual describing using the thermomelt stuff. It talks about doing tests with a test wheel in a tank though. I would have to attempt the same tests on the water. I may do it nonetheless.
69boo307	posted 04-19-2010 02:45 PM ET (US) Tom976, the thermostat is a good idea, I hadn't thought of that on the boat engine. I suppose a sticking thermostat could cause problems.
tedious	posted 04-19-2010 04:11 PM ET (US) TSB 2221 for the 60 and 70s changed out the temperature switch for a new one with a higher "trigger" temperature. If your motor does not have the new switch, it's quite likely that's the problem. I was suffering the same symptoms last year and have just ordered the new switch. Tim Info: SB 2221 Temp sensor new sensor pn 584166, tan/blue stripe wire replaces earlier part with plain, brown wire.
tedious	posted 04-19-2010 04:18 PM ET (US) Another potential contributor to the problem is covered by SB 2276R1 (relocate tattle tale nipple to top of block). Without this change, if you run through aerated water you can get an air pocket in the top of the block which can cause the top cylinder (where the temp sensor is located) to overheat. I'm guessing the new switch is most of the problem, but wanted to make you aware of this as well. Tim
69boo307	posted 04-19-2010 06:51 PM ET (US) Thanks Tedius! I took the the thermostat out when I got home and opened the housing. It wasn't corroded, but I did find a small piece of silicon gasket sealer in the housing, same as I used on the water pump housing. I'm wondering if it couldn't have prevented the little mechanism from opening fully?
jimh	posted 04-19-2010 11:09 PM ET (US) You need to get a water pressure gauge so you can see if the new water pump impeller installation was done properly and produces the proper water pressure. All this speculation about the over-heat alarm being false is only reasonable once you prove the water pump is putting out the proper pressure.
tedious	posted 04-20-2010 07:38 AM ET (US) In 69boo's case, Jim is quite right - since the problem seemed to come on very suddenly, coincident with an impeller change, it would make sense to verify that water flow is working as it should. It's also certainly possible that the piece of silicone goop was interfering with the flow in some way. However, in 69boo's case in the longer term and particularly in Dillon's case, if makes sense to change out to the newer temperature switch. From another forum the old switch appears to be a problem mostly when the water temperature is over 70, or running with a heavy load at mid-throttle. Dillon, this might be responsible for your apparently random triggering of S.L.O.W. mode. You mentioned that you did change the switch, but did they install the new version with the blue/brown wire or just a newer original, with the plain, brown wire? It would also be interesting to know if the telltale hose routing is correct on both these motors. If the telltale hose comes out of the side of the exhaust cover, the SB has not been performed. Tim
69boo307	posted 04-20-2010 07:56 AM ET (US) The fitting for my 'pee hole' is on the lower side of the cover, not the top. Is this a hard thing to change? I'm assuming you would plug the old hole and drill/tap a new one? Do you know if I can find the service bulletin online anywhere?
69boo307	posted 04-20-2010 08:02 AM ET (US) Found a good thread on the topic with a scan of the SB: http://forums.iboats.com/showthread.php?t=222677&highlight=pee+hole+tell+tale
tedious	posted 04-20-2010 08:14 AM ET (US) Yep, that's where I got a lot of my info. I have not found an actual online TSB, but there are a lot of good posts at that forum. I did the telltale changeover myself and got lucky - my motor had a new powerhead installed by the previous owner and the new block already had the upper hole drilled, so I just had to swap the telltale outlet with a plug rather than drilling and tapping. Even so, the drilling and tapping seemed fairly straightforward - the location is very accessible. Tim
69boo307	posted 04-20-2010 08:32 AM ET (US) Just an 'aside' comment, keeping this old boat engine working right has turned out to be very much like my hotrodding experiences with old cars. You run it for one weekend, then spend the next 2 weeks working on it :).
tedious	posted 04-21-2010 02:38 PM ET (US) I know what you mean! We got some good use out of our 70 last summer, but I don't have a ton of confidence in it. I had unpredictable S.L.O.W mode from time to time, two separate fuel leaks, and the idle was never great, mostly pretty bad - really made docking an adventure. I hope that with the idle orifice changes I made, the new prop, and the replacement temperature switch and new telltale routing, things are a lot better this year. Tim