Johnson 225 overheat alarm

[23robolo]

My '94 Johnson 225 ran great when I bought it last month but didn't charge the battery. After replacing the rectifier/regulator it charges fine, but now I get the overheat horn after a couple of minutes above 4000 rpm. I have replaced the water pump, pulled and cleaned the heads and replaced the thermostats. Disconnecting the starboard temperature switch eliminates the horn, so I replaced it as well, but it made no difference. Easing up to speed it will run nearly 4000 rpm without the horn. The temperature gauge shows warmer than before, but still in the green range. Any ideas?

 

[dragonslayer]

Re: Johnson 225 overheat alarm

I believe the 225 has a fuel restriction sensor that will activate if there is a fuel supply restriction. The warning would be the same as an overheat.

 

[Dhadley]

Re: Johnson 225 overheat alarm

If it's a fuel restriction the horn will stop as soon as you reduce throttle. If it's an overheat, the horn will continue to sound even after you come back to idle until it cools down. The rec/reg died because air is being trapped at the top of the block. This can be cured by venting the block on the starboard (high) side. I'm sure that was done when the rec/reg was replaced to prevent a repeat failure. <br /><br />Good luck!

 

[seahorse5]

Re: Johnson 225 overheat alarm

How did you clean the heads on that motor? The water outlet passageway is a lost foam casting and you cannot get inside of it to clean it.<br /><br />Since the stb. temp sender turns off the alarm when disconnected, I would pull that head off and inspect the plastic water deflectors in the cylinder block. <br /><br />Did you remove and inspect the "blow off" valve? Replace the valve tip with one from a '97 or later which has the air bleed screws. Check the hole with a drill bit to make sure it is clear.<br /><br />There are two different water pump kits that look alike for that motor, depending on shaft length. It a 20" shaft pump is installed in a 25" motor, it will overheat at high speeds.

 

[23robolo]

Re: Johnson 225 overheat alarm

The heads were cleaned with a pressure washer, which worked well on the channels around the pistons, but was limited inside the casting. What of it I could see with a mirror looked pretty good. The single water deflector on the stb. side was ok. Water pressure is good, up to 30 psi. What is a blow off valve?

 

[seahorse5]

Re: Johnson 225 overheat alarm

It is the pressure relief valve on the back of the motor, under the plastic housing with 2 hoses coming off of it. Remove the screws and pull off the housing, run a drill bit thru the hole to make sure everything is clear. The valve tip should be replaced, order a '97 or later one as it has grooves (not screws, from my earlier post) to bleed the air out. Replace the seal ring also. The blowoff valve and the thermostats work together at high speeds.<br /><br />I'll have to check a parts book, but I think there is more than one water deflector on the stb. bank.

 

[jegervais]

Re: Johnson 225 overheat alarm

Seahorse is correct, there are two water deflectors in the port bank, one on the top of the block deck and one on the bottom of the block deck.. They are red and white in color (sorry I don't remember which is which). The starboard bank has one deflector in the bottom of the block deck.<br /><br />Hey Seahorse, you think he could have the wrong waterpump kit installed. You know the split-line vs. non-split-line?? If the wrong kit is installed an engine can overheat or overcool depending on which combination is used, just can't remember... Boy have I got c.r.s. tonite... <br /><br />-John

 

[seahorse5]

Re: Johnson 225 overheat alarm

Ilini John,<br /><br />Read one of my previous posts, the pump is mentioned, you must have CRS or are getting old quick!

 

[jegervais]

Re: Johnson 225 overheat alarm

Hell, I musta' read the original post 3 times before I picked up on the water pump being changed! (LOL) Now you want me to go back & read your posts too!! I must be overdue for a good boat ride, it's just too cold up here yet...<br /><br />-John

 

[23robolo]

Re: Johnson 225 overheat alarm

The water pump is the same model that was there when it wasn't running hot. I went out in the gulf for a little fishing yesterday and it seems to be getting better. I could run 4400 rpm without getting the horn. I'm thinking I just got a couple of bad tanks of gas. Sorry about the cold up there and thanks to everybody.