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3.0 tks and alpha one overheating problem..

G

GKN

New member
hello. I am new to the forum. I am writing from Turkey.
I have a 2011 model bayliner 175 gt with my 3rd tks engine and alpha one steen drive. I removed and renewed the engine and stern drive for overheating problem and rectification. The engine is working properly. I also installed a new manifold. I did not change the exhaust riser.

"Regarding my main issue, there is no problem up to 3000 RPM after the engine starts. During this time, I reach a speed of about 16-17 knots. However, when I exceed 3000 RPM, the engine temperature quickly rises from 80 degrees to directly 125-130 degrees, and it does so very rapidly, taking just a few seconds to go from 80 to 125. If I ease off the throttle and slow down, dropping below 3000 RPM, the temperature quickly drops back down to 80-70 degrees within a few seconds. This rapid fluctuation in temperature, either rising or falling, is quite unusual.

To address this, I've checked the impeller, looked at the hoses coming from below, and noticed a significant amount of water flow. I removed the hose going into the thermostat housing while the engine was running, and water was coming out from there too. I also tried running without the thermostat, but the situation remained the same. I must be missing a simple step somewhere. If you have any insights on what this could be, I would appreciate it. I'm a mechanic and specialize in motorcycles. This developed as part of my own project, but I feel like I'm overlooking something. Thank you for your assistance."
 
Have you confirmed the temp is accurate? Water temps do not jump in seconds.

I would suggest, seeing as you have spent so much money already,

Have you replaced the temperature sender?

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The temperature sensor has been replaced. The alarm sensor is also new. An external laser thermometer gives similar readings. The incoming water suddenly heats up. When the gear is in neutral, you can rev the engine as much as you want without any issues. However, while in gear and moving, overheating occurs after 3000 RPM. It feels like hot gas is mixing into the water. When I disconnect the water hose going to the thermostat housing at idle, there is a significant flow, and the water is cold. The engine overheats only when it is under load.
 
sounds like you have adequate water flow TO the engine...in order for that water to COOL the engine, it needs to flow THROUGH the engine and then OUT into the exhaust...assuming the overhaul of the engine enabled the thru part, I'd say, at a minimum, you need to inspect the exhaust elbow to make sure it is open and flowing freely. the IR temp gun used on and around the elbow can provide some insight as well.

finally, on your temperature value, It would help some of us if you label the values with the appropriate scale...I'd be your posted values are deg C.
 
Sure, I'll include the Fahrenheit degrees: Up to 3000 RPM, the temperature stays at 175°F, but as I continue to accelerate, it rapidly rises toward 250°F.
1000153427.jpg
 
3 motors and they all overheat, wow

Remove the exhaust elbow and look down inside the exhaust toward the drive. Are the exhaust shutters there and also if they are there look under them and is anything blocking the exhaust exit out the drive?
 
The exhaust shutters are missing; they were removed during a previous engine repair. We didn’t reinstall them. There’s nothing obstructing the exhaust outlet. We haven’t been able to reach any solution. When it overheated before, I had removed the stern. The plastic S-pipe from the impeller inside the stern had melted. Perhaps this information could give you an idea.
 
if the pipe from the impeller housing melted, you are definetly dealing with some sort of obstruction in the drive. pull the drive and inspect the cavity below and around the impeller. then pull the cap off of the top of the unit and look for obstructions in the upper section, after that, check the hose behind the gimbal helmet and make sure it is not kinked at any angle. if the hose was repalced with anything but a merc molded hose, change it out for that hose,
32-8M0215001
i have had issues with the straight unmolded hoses kinking at full trim and causing a restriction.
once all those areas are addressed, remove the hose going into the thermostat and run a garden hose/house water, and see if the flow is smooth and does not seem restricted. the hose on the engine is 3/4 or 1" and the garden hose is usually 5/8 or less so the flow should be low, not under pressure, i hope that make sense. if the flow is restriced, then id inspect the hose from the gimbal to the thermostat and any thing in the path.

next reassemble everything, put another impeller kit in to be sure that is not the issue and take it for a ride., see what it does.

if you still have issue, i would run the boat with a clear hose section installed between the thermostast housing and the intake hose and see if there is a lack of water flowing when the engine is acting up.

keep us posted
 
you could be sucking exaust gases in from the impeller area. running ,not moving the exaust cavity is water filled, underway there is only exaust gas mixed with water exiting the motor
Drop the lower unit, install muffs and see where the water is squirting out from
 
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