'03 Johson 90 overheats despite new water pump

[tom_colson]

I got a J90 that's overheating (according to the alarm) despite a new waterpump. Motor is an '03, on a 19 foot sundance flatbottom, has been in only freshwater and been babied, not one SINGLE problem in 7 years of operation. Had an annual service done, and had a water pump put in. Mech checked everything else out, stat opened ok, original WP impeller wasn't burned up, and in his opinion, motor was "exceptionally clean". So now, at some random time interval, I get the overheat warning and engine shut down. There is no time to build up, it could be 1 or 20 minutes after engine start, but only in the water. On rabbit ears, it never overheats. I've run weed whacker trim line up the water jet, everything is clean as I can tell, prop is SS. Ran it on the ears for a while, flushed multiple times, back on the water, it keeps overheating. What the hell is causing this, something that a certified mech would miss when he replaced the pump and checked the stat? Desparate here, this is my work boat and costing me $$$ when off the water for the 5 hour trip to the shop!

 

[91kuhndog]

Re: '03 Johson 90 overheats despite new water pump

Tom,
Do this....it's summer time and the water temps are high enough to do this. Pull the thermostat out of it and run it. What might be happening is the stat is stuck and either not opening and/or closing all the way. When you run it on the hose with 70* water, it runs just below the max. temp. You put it in the water where it's being cooled by 90* water, and it's hitting the 161* mark and setting off the horn.
Just a collectivethought. You have a good pump and no water restriction coming in....so something is blocking water from coming out. I would pull the stat and run it.....I'd been comfortable in betting that you'll find a bad stat in the motor. Let us know what oyu find.

PS....is the motor pssing out the hose?

 

[tom_colson]

Re: '03 Johson 90 overheats despite new water pump

output stream is just fine; water temp is 76 f (part of this job requires recording temp daily); mech said stat was opening under the "correct range of temp conditions", assuming he's got some gizmo to check that. Problem is, I don't have a stat gasket "handy", so if I pull the stat, I'm dead in the water till I make this 5 hour drive to the only shop that can turn me around in a day.

On restart, output water is pretty warm as it bleeds the heat off the block for about a minute then cools down.

 

[91kuhndog]

Re: '03 Johson 90 overheats despite new water pump

Tom,
If you have some silicone handy.....I'd pull the stats. I had a 105 V-4 and had the same problem (several years back). I had brand new stats in the motor, but one had stuck. If you have silicone, gently pull the cover and remove the plug/spring and thermostat. Seal it, and reassemble. Let it sit for about 30 minutes to set, then run. Also, is it running good when the motors running (firing on all cylinder's?) Also, could you have sucked sand/small rocks up into the motor? I worked on a guys jet boat a few years back that had an obstruction under the right water jacket cover causing the head temps to run higher on the lower cylinder. It turned out he grounded the boat and sucked a lot of sand into the motor.

 

[tom_colson]

Re: '03 Johson 90 overheats despite new water pump

but then wouldn't I be running with no stat? if there is a blockage problem, couldn't I run the danger of warping the head? according to the mech, the compression check out ok.

 

[91kuhndog]

Re: '03 Johson 90 overheats despite new water pump

Tom,
If its a bad stat, you can run the motor without a stat as long as the water temps are relatively warm. This will help to eliminate a thermostat as a potential problem plus, without the thermostat out of the head, it'll increase the water flow through the cooling chambers and can flush any debries out that might be stuck in there. I don't think you have a cooling issue since it'll run on the hose, I think you have a thermostat issue. That's what I'd look at next. In the saltwater here along the coast, we change thermostats every year when we change out O2 pumps.

 

[tom_colson]

Re: '03 Johson 90 overheats despite new water pump

I'm going to try that: also fedex overnight for a 60 and 70 deg stat, AND a water pressure valve AND a return hose (I always tear them up when I pull them). Bear in mind, I'm no mech: just a desparate guy losing $$$ when this thing don't work. BTW, the output psssr stream was a little warmer than I like after 2 hours at 2-3 k rpm, but no overheat. Is this bad?

 

[tashasdaddy]

Re: '03 Johson 90 overheats despite new water pump

put the correct stat back into it. it is there for a reason, so the motor runs at optimum temp.

 

[tom_colson]

Re: '03 Johson 90 overheats despite new water pump

what would the correct stat be? 60 or 70?

 

[bob johnson]

Re: '03 Johson 90 overheats despite new water pump

how do you know the motor is overheating and not a bad alarm???

when the alarm goes off check the temperature of the head with an outside sourse....heat stick, your finger( if you cant hold it there for 3-4 seconds its too hot), or an infared thermometer.

you need to verify that the alarm is valid.....

after you verify that the head is actually too hot,

then you can start to diagnose and remedy..

good luck

biob

 

[tom_colson]

Re: '03 Johson 90 overheats despite new water pump

So I've replaced the thermostat (60 deg), water pressure valve, and spark plugs (just for the heck of it), flushed top to bottom (no sand or veg came out). Runs great on the hose. Soon as I put this in the water, though, overheats in minutes. What could be causing the overheat problem?

 

[bob johnson]

Re: '03 Johson 90 overheats despite new water pump

you could help yourself if you methodically answered what is asked....

how do you know the motor is overheating????


alarm?
temp guage?
infared thermometer?
heat stick?
touch?


do you say it is overheating because you hear an alarm???
'
I have a similar motor and have some over heat issues myself...
I have armed myself with manuals infared thermometers dual temp gaunes, water pressure gauges... and is till am chasing my issues...

so EVEN with some of the RIGHT INFO it can be troublesome to diagnose over heat issues..

and what do you mean by (60 degree) thermostat???

is that the style motor,( they make 60 degree angled blocks and 90 degree angled block) or the temperature the thermostat operates at??

are the tstats metric or english

normal t-stats are about 140 degrees!!!!


good luck

bob

 

[tom_colson]

Re: '03 Johson 90 overheats despite new water pump

heat alarm
WWAYYYYYY too hot to touch
pss stream is SIGNIFICANLY hotter than normal

 

[tom_colson]

Re: '03 Johson 90 overheats despite new water pump

Motor is a J90PL4STS (st8 4, EFI). 60 degree is metric, when you order them you get your choice of 60 or 71 degere. 60 was what was in the motor to start with.

 

[bob johnson]

Re: '03 Johson 90 overheats despite new water pump

Motor is a J90PL4STS (st8 4, EFI). 60 degree is metric, when you order them you get your choice of 60 or 71 degere. 60 was what was in the motor to start with.

is that a 4 stroke????

I guess i assumed you had a 2 stroke

whole different animal.....than a 2 stroke....

best of luck


bob