Cooling question on 1989 Johnson GT150

[Tregs]

I recently changed the impeller and exhaust gaskets (first time) after reading several threads on this forum. I fired it up today on the water hose. I let it run for about 30 seconds, with my hand on the block and heads to see how hot it was getting. I let it run until it got too hot to touch. I never saw return water coming from the discharge valve on the starboard side of the motor, just under the cowling. I didn't replace the thermostats, although I would have if I knew where they were.

My questions:
1) How long does it usually take for the water to circulate through the engine and out the discharge valve? The buzzer wasn't buzzing, but I'm not sure that it works. I don't have one of those IF thermometers.
2) Do the thermostats have to open before the water exits the discharge valve?
3) where are the thermostats?

Thanks in advance for your help.
Tregs

 

[ob]

Re: Cooling question on 1989 Johnson GT150

I assume you are refering to the tell-tale line that indicates that the water pump is putting out. Try tracing the hose back to the engine block and remove it. Then using a coat hanger or suitable probe,clear any crusty obstructions that may be hindering flow and reconnect and try again on the hose.The lower cowl orifice that the water discharges from may also be obstructed. Check it as well.

The T/stats for your engine are located at the top of each head cover.There are twne for each bank. They have four fasteners for each t/stat cover I believe.

 

[Will Bark]

Re: Cooling question on 1989 Johnson GT150

On my 1987 150hp Johnson, it takes more than 30 seconds on the muffs for the thermostats to open because of the cooler water. If your tell tale is not squriting water as the engine starts then you may have something stopping it up; try running a weedeater line up thru the hole to see if it's blocked. Good luck.

 

[Tregs]

Re: Cooling question on 1989 Johnson GT150

Thanks for the replies. I traced the hose from the discharge orifice up over the starboard head to the bottom of the block. I pulled it off the block and blew thorugh it. No obstruction, so I guess water isn't getting to that point (if it is supposed to flow out of there as soon as the engine is running).

I was careful to get everything lined up when I reinstalled the lower unit. The only thing I wasn't sure about was the rotation of the impeller, it was a tight fit so I had to curl the fins to get it to fit in the housing. I watched youtube videos to make sure I curled them the correct direction, but there were no videos on my specific engine, so I just went with an Evinrude video.

When the engine starts, water comes out of a couple of other small holes in the lower unit, but not the one up by the head.
Any ideas before I pull the lower unit again?

Thanks Again.
Tregs

 

[ob]

Re: Cooling question on 1989 Johnson GT150

Did you probe the hole in the block as well to insure it is clear? Otherwise I'm assuming that you've had this engine for a while and have watched it run on the hose. Water should discharge from the indicator line in just a few seconds after starting engine.If it worked before you replaced the pump it's likely not the problem. If you drop the lower unit again pay close attention and insure the water pump discharge tube is aligned and its grommet is in place when lifting the lower unit back together.

Many times the impeller will right itself if installed with flutes aiming counter rotation. Nothing is a sure thing though.

 

[Tregs]

Re: Cooling question on 1989 Johnson GT150

Thanks again for the reply ob. The boat has been in the family for many years, but it just recently was given to me. I have spent many hours in the boat but it's never been run on a hose. Water has always come out of the indicator line while its running in the lake. I assume the hose is no different so I'm sure it's something I did.

I was careful to watch that everything lined up when I put it back together. Since this was the first time for me to drop a lower unit, I read as many threads as I could find before doing so. I've restored several cars soIi'm no stranger to engines and wrenches. I sure thought I got it put back together right. I'll pull the indicator line off the block tomorrow and see if anything is plugged. Maybe some trash from when I sanded and repainted the lower unit while it was off.

Thanks,
Tregs

 

[metriccrescentwrench]

Re: Cooling question on 1989 Johnson GT150

I let it run until it got too hot to touch.....

At idle the temps are supposed to be around 145 F as I recall. At that temperature you're only going to be able to hold your hand on the head for a few seconds.

How long does it usually take for the water to circulate through the engine and out the discharge valve?

On my 200 when running on muffs it can sometimes take a couple of long, excruciating minutes to get an indication on my water pressure gauge or for water to exit the tell-tale.

The buzzer wasn't buzzing, but I'm not sure that it works.

There's a temperature switch in the top of each head, the switch closes on an overheat condition. You can test your buzzer by disconnecting the brown wire from the temperature switch and grounding it (the end that goes to the wiring harness).

I don't have one of those IF thermometers.

For 30 bucks or so from Harbor Freight it's worth getting.

 

[emdsapmgr]

Re: Cooling question on 1989 Johnson GT150

The telltale is plumbed into that part of the block which gets cooling water from the lower unit first-ahead of the thermostats. You should have water pressure to the telltale within the first 10-20 seconds after startup. Did you replace the key on the driveshaft when you installed the new impeller?

 

[Will Bark]

Re: Cooling question on 1989 Johnson GT150

You can also get that IF thermometer at Lowe's if you don't have a Harbor Freight close by.

 

[Tregs]

Re: Cooling question on 1989 Johnson GT150

I did replace the key on the shaft. Great question though.
Thanks for info on the tell tale plumbing. It sounds like I should be getting water out the tell tale regardless of thermostats.
We have a Harbor freight close by. I'll drop by on my way home from work and pick up a thermometer.

Thanks for the help.

 

[emdsapmgr]

Re: Cooling question on 1989 Johnson GT150

Yes, that's correct. The telltale will indicate the general condition of the impeller. The stats are at the end of the cooling cycle, and regulate the water leaving the block. You can have a good/working impeller and have an overheat at idle if one (or both) of the stats stick closed.

 

[Tregs]

Re: Cooling question on 1989 Johnson GT150

Tonight's update:

I pulled the telltale tube and ran weedeater line up through the block as suggested, then ran it all the way through the tube and out the outlet. It must have done the trick because it started squirting water as soon as I fired it up. I noticed that one head heated up quickly and the other one stayed cool. I pulled the thermostats. Starboard is stuck open. No paint chips on the thermostat bolts leads me to believe these are 22 years old. I ordered new ones along with a pair of poppet valves.

On another note, I noticed that the prop doesn't turn when I put it in gear. i must have missed the gear rod eye when I put it back together. I'll fix that while I'm waiting for the thermostats to arrive.

Thanks for the help.