15 johnson has water at the tell tale hole but still overhea

Last year I got into some low tide silt and I overheated my motor. Over the winter I pulled and replaced the headgasket and the thermostat, I went out the other day for the second time out and overheated again. Now I have plenty of water at the Tell tale hole. I,ve pulled the head replace yet another head gasket and checked and cleaned the thermostat. Fired it up have ample water at the tell tell , still gets hot . Whats next? it's a 1985 15 hp jonhson. Thanks in advance.

Try the water pump.......! When you get it apart look at the cup for grooves at the top and the bottom plate for grooves as well. If you can feel the grooves with a fingernail replace the complete pump assembly. Know that's more expensive but alot cheaper than a powerhead!
You're apparently in salt or brackish water so you may also have the grommets at the top of the water tube melted and blocking flow or corrosion build-up behind them and pushing them shut. The vintage engine you have is prone to this. Would be enough water for the telltale but not able to pump enough volume to cool the engine on plane or higher. You must pull the powerhead to replace those. Not a hard job and all you will need are two grommets and a base gasket. Good time to do the pump and all the fuel lines at the same time.

I had a very similar problem with an older 15 hp Johnson. It overheated, shut down and restarted when cooled. The pee stream was good at times and non existent at other times, but still ran.

I did the normal replace the impeller trick but that did nothing. I tried forcing water up the intake tube in the lower unit and a pee stream came out, but not the normal force. I removed the thermostat and it worked alright so decided to check the water passages in the head. It looked okay. I read on the web about a guy who modified the elbow on the tell tale hose by drilling a hole in the elbow and inserting a wire or something similar directly into the cooling jackets. I did that and used a weed wacker line string and was able to shove more than a foot of it through the jackets! I then blew some compressed air into the hole in the elbow and you should have seen how much sand, silt and krap came out of the hole below the thermostat! BTW, plug that new hole with a machine threaded screw and drill a new hole in the lower cowling to accomodate that screw. If you need to clean out the pee hole while on the water, it makes it a lot easier!

Just because you have a pee stream, doesn't mean the water is making it through all the cooling passages.

Good luck.

Thanks For the replies, NoMo, when I had the head off I pulled the water jacket I cleaned it throroughlyand then replaced the thermostat. The port your referring to that had the silt and sand came out, was that the port on the head on the bottom? When i just replaced the head gasket I tried to run a wire up in there and didn't get very far. Is there a small orvice there? I did blow compressed air in that port and the slotted port at the top. I can see now that all it would have done was blow stuff back into the head. What if i removed the left side plate would that allow me to check and clean it better? Thanks in Advance!

Pappy said:

Try the water pump.......! When you get it apart look at the cup for grooves at the top and the bottom plate for grooves as well. If you can feel the grooves with a fingernail replace the complete pump assembly. Know that's more expensive but alot cheaper than a powerhead!
You're apparently in salt or brackish water so you may also have the grommets at the top of the water tube melted and blocking flow or corrosion build-up behind them and pushing them shut. The vintage engine you have is prone to this. Would be enough water for the telltale but not able to pump enough volume to cool the engine on plane or higher. You must pull the powerhead to replace those. Not a hard job and all you will need are two grommets and a base gasket. Good time to do the pump and all the fuel lines at the same time.

Click to expand...

Spin fisher,

1) you checked the water jackets and cleared them....great
2) you checked the thermostat...great
3) please take Pappy's advice and evaluate the water pump, cup and housing...if you haven't done so

4) the water tube grommet that pappy was referring to is at the top of the water tube at the base of the powerhead. Those have known to become distorderd and swollen to prevent good flow of water up or even block water flow to the power head dispite a good functioning water pump. If I am not mistaken, you will still get a stream of water coming from the indicator even though there is no flow going to the head. The water indicator only tells you the water pump is working not that it flowing through the head and around the water jackets!!

You will need to remove the powerhead and inspect the grommet at the base of the powerhead. Here is a YouTube video of a 9.9hp evinrude...basically same motor different Hp. It make a good reference to the upper water tube grommet at the base of the power head.

https://www.youtube.com/user/cpgixxer#p/u/65/cqYiFl6I_20



I hope this helps...good luck!

On your engine you will have two tubes and two grommets. One for supply and one to dump water.

I drilled out the 90 degree tell tale elbow on the starboard side of the motor and plugged that hole with a machine screw so instead of trying to send a wire or something up the tell tale hose, I could now send a wire directly into that side cover without taking it off. I also sprayed some WD40 into that hole and let it sit for a day then blew compressed air into it and that's when all that gunk came out of that hole directly below the thermostat.

As far as that water pick up tube from the pump, I also found on the web that by using a coat hanger with a curled end so as not to damage any seals and shove it up the tube from the pump into the power head might dislodge junk and open up that problem area described by others. Of course by doing this you're operating blindly so beware. My problem was pretty bad so I really had nothing to lose at that point.

Good luck.

cajuncook1 said:

Pappy said:

Try the water pump.......! When you get it apart look at the cup for grooves at the top and the bottom plate for grooves as well. If you can feel the grooves with a fingernail replace the complete pump assembly. Know that's more expensive but alot cheaper than a powerhead!
You're apparently in salt or brackish water so you may also have the grommets at the top of the water tube melted and blocking flow or corrosion build-up behind them and pushing them shut. The vintage engine you have is prone to this. Would be enough water for the telltale but not able to pump enough volume to cool the engine on plane or higher. You must pull the powerhead to replace those. Not a hard job and all you will need are two grommets and a base gasket. Good time to do the pump and all the fuel lines at the same time.

Click to expand...

Spin fisher,

1) you checked the water jackets and cleared them....great
2) you checked the thermostat...great
3) please take Pappy's advice and evaluate the water pump, cup and housing...if you haven't done so

4) the water tube grommet that pappy was referring to is at the top of the water tube at the base of the powerhead. Those have known to become distorderd and swollen to prevent good flow of water up or even block water flow to the power head dispite a good functioning water pump. If I am not mistaken, you will still get a stream of water coming from the indicator even though there is no flow going to the head. The water indicator only tells you the water pump is working not that it flowing through the head and around the water jackets!!

You will need to remove the powerhead and inspect the grommet at the base of the powerhead. Here is a YouTube video of a 9.9hp evinrude...basically same motor different Hp. It make a good reference to the upper water tube grommet at the base of the power head.

https://www.youtube.com/user/cpgixxer#p/u/65/cqYiFl6I_20



I hope this helps...good luck!

Click to expand...

Will do!

I'm just trying to collect as much information as I can before I sit down and take it apart. It's like a watch , I don't want to have something go shooting past my ear and not know what it is! I will be ordering parts I figure to replace as much as I can so i don't have to go back for awhile. Thanks for all your comments. Spin

Can someone tell me if I can remove the sideplates on the right side? I see a motor mount there. How difficult would it be and do I need special tools? Thanks.Spin

Should be no need to remove any plates on the powerhead, the mounts are secured by standard 1/4x20 bolts around 1 1/4-1 1/2" long and you should be able to loosen them with a 7/16" swivel socket on 1/4" drive tools. Again, you will need two grommets and a base gasket. Gasket sealing compound would be a good idea as well and, in addition to the gasket, you can coat the threads of the fasteners as you go back together with the compound to insure the engine will come apart later if need be.

Thanks ,Pappy. I did remove the lower unit last night. Everything came out fine and the impellor is a definite must replace. I was able to check the gormmets and appear to be good. While I had the lower unit off, I removed the tell tale nozzle and shot some wd-40 up in there and waited, then blew some compressed air up into the hose. I did the same thing on the water pump tube. While I was blowing air out of the water pump tube I was hit by something out of the pee hole line! Maybe that was my obstruction. Any way I bolt it back together and ran it . The motor did not get as hot as it was getting and cool down alot faster than before. I used my infared Thermometer and it was showing 145-160 deg. on top of the power head and 120- 140 on the water jacket. What is your thoughts? Thanks Everyone!

You should be running around 135 deg. at idle. The engine was designed to run on the thermostat at idle RPM and to by-pass the thermo at speed. Check it there and get the numbers for me. Shoot the top of the cylinder head and the top of the block at the cylinder head.

Can anyone tell me what the port/hole is in the front of the lower unit is? Thanks

spinfisher said:

Thanks ,Pappy. I did remove the lower unit last night. Everything came out fine and the impellor is a definite must replace. I was able to check the gormmets and appear to be good. While I had the lower unit off, I removed the tell tale nozzle and shot some wd-40 up in there and waited, then blew some compressed air up into the hose. I did the same thing on the water pump tube. While I was blowing air out of the water pump tube I was hit by something out of the pee hole line! Maybe that was my obstruction. Any way I bolt it back together and ran it . The motor did not get as hot as it was getting and cool down alot faster than before. I used my infared Thermometer and it was showing 145-160 deg. on top of the power head and 120- 140 on the water jacket. What is your thoughts? Thanks Everyone!

Click to expand...

There is nothing that you can be hit by coming from the pee hole line that will overheat your engine. That line is simply an indicator line.
You cannot check the grommets by blowing air up the water tube (God, I wish it were that simple!). No, the coat hanger won't work either.....
Your engine should be running around 135 degrees at idle and should cool down once on plane.
Hopefully your impeller will do you some good.

Pappy said:

spinfisher said:

Thanks ,Pappy. I did remove the lower unit last night. Everything came out fine and the impellor is a definite must replace. I was able to check the gormmets and appear to be good. While I had the lower unit off, I removed the tell tale nozzle and shot some wd-40 up in there and waited, then blew some compressed air up into the hose. I did the same thing on the water pump tube. While I was blowing air out of the water pump tube I was hit by something out of the pee hole line! Maybe that was my obstruction. Any way I bolt it back together and ran it . The motor did not get as hot as it was getting and cool down alot faster than before. I used my infared Thermometer and it was showing 145-160 deg. on top of the power head and 120- 140 on the water jacket. What is your thoughts? Thanks Everyone!

Click to expand...

There is nothing that you can be hit by coming from the pee hole line that will overheat your engine. That line is simply an indicator line.
You cannot check the grommets by blowing air up the water tube (God, I wish it were that simple!). No, the coat hanger won't work either.....
Your engine should be running around 135 degrees at idle and should cool down once on plane.
Hopefully your impeller will do you some good.

Click to expand...

Papp, I got my new impeller installed and ran it last night, I have quite the improvement of volume and pressure. Yet , I'm not seeing any water at the exhaust port above the lower unit and it is still running to hot.

What is it I need to do to get to the water outlet grommets? To remove the engine I remove the lower unit , then there is 4 bolts under the cover, what about the 2 bolts at the lower pivot? I guess what I'm asking is how to remove the covers and access the grommets?. The video that somebody else made reference to shows the engine out already , not how to disemble the motor.

You folks have been really great and I am very thankful for all the comments and help.

The powerhead has to be removed. Once it has been removed then the exhaust plate beneath the powerhead can be removed and the grommets replaced. There are two on your engine. This is an easy job. A little time consuming, but easy. Your comment on not seeing water coming from the "exhaust port" above the lower unit is interesting. There is no exhaust port above the lower unit unless you are talking about the exhaust relief just below the powerhead and lower pan. Usually no water comes out there. If however you are talking about the several holes just above the cavitation plate at the rear of the lower unit those are thermostat relief holes and you should see flow once the thermostat opens.

Thanks Pappy, yes thats the ports I was reffering to (4holes above the cavitation plate). I'm anxious to tear into it, but I'm waiting for parts. When they talk about 6 bolts are they talking about the 4 bolts at the driveshaft housing and the 2 bolts below the steering shaft? We have a new salmon season starting in july and I hope to have this boat back in the water. Thanks for your expertise. And Happy Father's day! Spin

Go get your gasket and grommets. Also get gasket sealing compound and new fuel lines. When you have your gasket in hand you will see the location of the outer 6 holes that are used for powerhead mounting.

Okay Folks, I got the powerhead off last night and sure as heii the outlet tube was plugged. I went ahead and replaced both grommetts (one for the supply and one for the outlet side), the base gasket and now I'm ready to re-assemble. Didn't change the fuel line it was replaced a year ago, but I did a thorough cleaning on everything. Once I get it back together I'll let you know how it went. Again thanks for all your help! Spin

Well, low and behold , I got the motor all bolted back together and tighten down , ran it on the muffs for about 35 min, running beatifully! Warm to the touch, not the pippin' hot temps it was running at. At idle you can watch the tell tale stream pulsating as the thermostat opens and closes. Started up with 5 pulls, thats what I've always liked about this motor , starts right off everytime. Idles great and I'll be on the California Delta come Monday AM.

Thanks to all the tinboaters who left comments , you made this alot easier than what I thought it would be, thanks to Paradise marine in Stockton for parts and advise.

Spin