Way to HOT

[OFF THE CLOCK]

Hello to all. If owned Ev engines in the past this is my first Johnson. Here is the deal I picked up a engine that had been sitting for awhile I went through the carburetors and changed the waterpump complete new plugs new thermostats kit etc etc. Now i took the boat down to the ramp and Let it idle in the water. The water is coming out of the pisser. But the heads got hot to where I couldn't keep my thumbs on the heads. I checked the temp at the heads ant the Tstat block and everywhere else. (now there was no alarm) but I know this wasn't right temp. I was raised up around these johnson EV engines so I know when there not running correctly. I'm also tooled for major tear down overhaul. And I do have a manual.!So I figured I'd pull the flow hoses off and make sure water was moving around the heads. Started it up there is flow. temp went down (101'ish @ the Heads) Of course. So I took it back home pulled the tstat housing after I bought a kit. When I removed the housing I found a new Purple springs and caps the tstats look good. I replaced them anyway with the kit.Cleaned the housing cleaned the inners pulled the lower unit inspected the lower end with a flashlight. Hooked up a hose to the input tube ran water through it it ran out the heads. Looked inspected looked somemore etc etc. reinstalled back to the ramp/ same issues. Took it back home removed the tstats reinstalled same Issues. Hot at the heads.

I know the older engines would spit water out the 2 holes just below the cowling this one dose not either in the water nor with muffs. Also the 6 holes on top of the cavitation plate. no water coming out there either. I'm at a total loss on where to look other than pulling the block off the base. Any Idea on this? I hope I'm being descriptive enough. I'm no rookie but I don't know everything. Tooled for Major overhaul and had a couple down to the nuts and bolts. Any help would be great. I posed this same questio in another form but this must be for only the skilled to answer. I'm not wanting to bring it in anywhere for the cost would be great chasing a blockage but if I must pull it apart I will do this also. This engine was rebuilt sometime ago and the original owner was an older fella (meaning no dogging it). and it idles like four guys hitting drums not a loose engine would run bang ..bang..bgbg.bg bang this engine is tight with like new compression so I don't want to hurt it by trying to figure it out.. Thanks so much for reading this and in advance thanks for the help..

Signed.

OFF THE CLOCK.

 

[emdsapmgr]

Would really be helpful to know just what engine you are working on. Sounds like you are working on either a V4 or V6 engine, what with the mention of two heads. The dual hoses would describe an older crossflow type V4, same with the dual stats and single thermostat housing. Just because the telltale is functioning does not mean that cooling water is circulating through the powerhead. If you don't get water through the stats, you won't get any water to the exhaust relief ports. There are two aspects to the thermostat housing on a crossflow. 1. at idle, all the water goes through the stats. If they can't warm up, they will not open. Make sure the two pinholes in the thermostat valve body are open/clear. If they are plugged with debris, the engine will overheat at idle. (Late crossflows have a single oval hole.) 2. Once you rev the engine or the boat gets up on plane, the extra water flow will force open the two pressure relief valves in the therm hsg. That will flood the powerhead with tons of extra cooling water. Even with the stats stuck shut, the open pressure relief valves are enough to cool the powerhead as long as it is on plane. As soon as the engine drops back to idle, it can overheat again. Your stats open at 143 and should keep the engine between 143 and 155 when idling in the middle of the summer. Higher than that is a problem.

 

[OFF THE CLOCK]

Would really be helpful to know just what engine you are working on. Sounds like you are working on either a V4 or V6 engine, what with the mention of two heads. The dual hoses would describe an older crossflow type V4, same with the dual stats and single thermostat housing. Just because the telltale is functioning does not mean that cooling water is circulating through the powerhead. If you don't get water through the stats, you won't get any water to the exhaust relief ports. There are two aspects to the thermostat housing on a crossflow. 1. at idle, all the water goes through the stats. If they can't warm up, they will not open. Make sure the two pinholes in the thermostat valve body are open/clear. If they are plugged with debris, the engine will overheat at idle. (Late crossflows have a single oval hole.) 2. Once you rev the engine or the boat gets up on plane, the extra water flow will force open the two pressure relief valves in the therm hsg. That will flood the powerhead with tons of extra cooling water. Even with the stats stuck shut, the open pressure relief valves are enough to cool the powerhead as long as it is on plane. As soon as the engine drops back to idle, it can overheat again. Your stats open at 143 and should keep the engine between 143 and 155 when idling in the middle of the summer. Higher than that is a problem.

Thank yo for your reply. I'm working on a 1985 Johnson. J90TLCOS. I had the engine idling in the driveway with the muffs on and it was up to 153fht and climbing I never got a hot horn with the muffs on i didn't want it that hot. I removed the tstats and got the boat up on plain it ran for about a mile and the hot horn went off. I shut it down removed the flow hoses from the heads and waited a few minuets started it up the buzzer was buzzing then the flow of water cooled it down ran it back to the ramp. When I had it ALL APART I cleaned the housing with care removing all signs of buildup. I hooked the water hose up to the inlet tube (bottom side water impeller inlet) there was flow. I just dont understand why it gave a hot horn even while the tstats were out there is a blockage somewhere I just dont know where to look . unless like you said while the boat is on plane there is a port where the extra cooling water comes from. Could you describe the location of where this inlet system is? And the starting point in the lower and the exit point . there might be a blockage in that hince why it might not be getting enough cooling water from the Valve system

Also if I understand you correctly, your saying in short the impeller water flow takes care of cooling while @ idle and lets say drilling along for that speed =that amount of cooling water then @ higher speed the cooling water is picked up by the pressure (squeeze) of the lower unit moving through the water opens the spring relief valves for cooling at that engine speed=more heat more cooling. it has a dual cooling system that works independently (depending on scenario) under different loads? Am I on point or at least in the same game? Thanks again

OFF THE CLOCK.

 

[emdsapmgr]

The cooling system is all one. You are correct: When idling, the lower unit impeller does all the heavy lifting, sucking and pressurizing water up to the powerhead. When your boat is on plane the force of the oncoming water overcomes the pump action forces tons of extra water (and pressure) up the same pipe-and causes the pressure relief valves to open. Same system. The water intake is the pair of intake grilles right ahead of the prop. The exit is into the exhaust adapter just under the powerhead. What did the holes look like in the valve body inside the thermostat housing? As much as the cooling system is discussed, mention should be made of the cooling parts of the block. That powerhead has rubber water diverters by each cyl-to direct water flow around each cyl. If these rubber diverters become mis-located or if debris clogs them up, you will get an overheat, even with a functioning water cooling system. See picture. The rubber diverter to the left is correctly positioned, the one on the right is out of place. The space around the diverter needs to be open-as pictured. Also, if there is debris inside the head covers, the cooling passages may not pass water properly. Your water test with the hose would seem to indicated that neither of these last two comments would apply... since you get water out the hoses.

 

[OFF THE CLOCK]

The cooling system is all one. You are correct: When idling, the lower unit impeller does all the heavy lifting, sucking and pressurizing water up to the powerhead. When your boat is on plane the force of the oncoming water overcomes the pump action forces tons of extra water (and pressure) up the same pipe-and causes the pressure relief valves to open. Same system. The water intake is the pair of intake grilles right ahead of the prop. The exit is into the exhaust adapter just under the powerhead. What did the holes look like in the valve body inside the thermostat housing? As much as the cooling system is discussed, mention should be made of the cooling parts of the block. That powerhead has rubber water diverters by each cyl-to direct water flow around each cyl. If these rubber diverters become mis-located or if debris clogs them up, you will get an overheat, even with a functioning water cooling system. See picture. The rubber diverter to the left is correctly positioned, the one on the right is out of place. The space around the diverter needs to be open-as pictured. Also, if there is debris inside the head covers, the cooling passages may not pass water properly. Your water test with the hose would seem to indicated that neither of these last two comments would apply... since you get water out the hoses.

Again Thank you for your reply. The passages looked clear in the thermostat block. As far as the rubber tubes (in picture I'm unsure) I did speak to a guy today and he was saying that there is a valve that is suppose to open (aside of the spring relief valves) that lets the water into the heads for cooling The name escapes me right now. But he said if it is stuck closed the water will not force up into the spring vale to exit. Have you ever heard of another valve like this the valve name begins with the letter (P). Anyway I'll have a look into the water Jackets (behind the heads) to see if the rubber tubes inside are misaligned or clogged I know there is flow out to the tstat just no exiting.. or not enough getting to the party under load. Thanks so much for your input on this issue. You definitely have a handle on outboards.. So again thank you..

Signed
OFF THE CLOCK.

 

[OFF THE CLOCK]

Then again this word for this valve he said it is under the or part of the exhaust the letter (p) might have be a slang term I should have wrote it down .. I was out on my bike and thought I would remember but I forgot. SMH..!

 

[OFF THE CLOCK]

PEKO valve I think it was.. Now that I did some reading I think he meant poppet valve. Also dose the thermostat go through the cork o ring ? or dose it go behind? I'm a little confused on this being that the book shows it one way and other images show it behind the thermostat. Thanks again..

 

[OFF THE CLOCK]

The cooling system is all one. You are correct: When idling, the lower unit impeller does all the heavy lifting, sucking and pressurizing water up to the powerhead. When your boat is on plane the force of the oncoming water overcomes the pump action forces tons of extra water (and pressure) up the same pipe-and causes the pressure relief valves to open. Same system. The water intake is the pair of intake grilles right ahead of the prop. The exit is into the exhaust adapter just under the powerhead. What did the holes look like in the valve body inside the thermostat housing? As much as the cooling system is discussed, mention should be made of the cooling parts of the block. That powerhead has rubber water diverters by each cyl-to direct water flow around each cyl. If these rubber diverters become mis-located or if debris clogs them up, you will get an overheat, even with a functioning water cooling system. See picture. The rubber diverter to the left is correctly positioned, the one on the right is out of place. The space around the diverter needs to be open-as pictured. Also, if there is debris inside the head covers, the cooling passages may not pass water properly. Your water test with the hose would seem to indicated that neither of these last two comments would apply... since you get water out the hoses.

I'm going to also have a look at this inlet forward of the prop. I also have the engine sitting at the lowest point on the boat. My other 115 1974 is was in the same holed in the transom. So it is safe to say the lower unit is low enough in the water for pickup (I believe) if my memory serves me correct you can just see the top of the cavitation plate intermittently in the water while on plane. Just below or about even with the bottom of the haul..I also did some reading and someone said that if you trim the springs to allow easy flow of water into the heads. Seems a bit much.

 

[Fed]

Poppet valves, just another name for the pressure release valves.
One thing you haven't sort of directly answered, were the two tiny bypass holes in the thermostat housing clear?

 

[emdsapmgr]

Mercury's use poppet valves, the OMC's call theirs pressure relief valves. Those valves will open when the engine is revved in neutral, or when the boat gets up on plane and the onrush of water causes them to open. Those nylon valves don't fail often, but they may not work well if they become heat-deformed. How did they look when you had them out of the housing? Sounds as if you have the engine mounted correctly. The water flowing from under the transom should go just under the anti-ventilation plate.

 

[OFF THE CLOCK]

Well I will give a update on this issue. I had went back to start. I posted my skills in working with engines and tooled with more than I'll ever need and had forgotten more then most will ever learn. I pulled the heads (the first place to look) and found swelled hoses in the block.then I split the heads again found more blockage. So it is safe to say this was my WAY TO HOT. Rebuilt replaced cooling proper now. Found a new Issue...!!