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Desperado213

F115 2 Stroke Engine Overheating

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So now that its getting a little warmer I want to start getting my 18' Lappy ready for the water again after sitting. Before winter the motor would throw the overheating alarm and shutter down. I took it to a Yamaha service mechanic who changed out the impeller and the foot oil. I took it out when I got it back and it did the same thing even though it was peeing stronger than ever. I put the tarp on it and said I would deal with it when Winter was over. The motor is a 1999 115 2 Stroke. I was seeing if anyone may know what I could check. I am thinking it is a faulty thermostat somewhere. I can cruise around 25-30 and it will not throw the alarm. It only shutters down at full throttle or close to it.

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Go through the thread above about the ProV having the same issues.  Yamaha 2 strokes are notorious for clogged cooling passages in the heads and block.  Also time to change both Tstats and your entire poppet valve system.  Use compressed air to see if the poppet valve passage is clear.

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More than likely its poppet valve related. I was religious about flushing my boat with fresh water on the ears after every use. When I pulled the heads there was some minor blockages in the water passages but not enough to overheat I don’t think. Glad I cleaned them all out though. Check that hose on both ends and like Lap it Up said , shoot some air in there and blow it out good. 

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Appreciate the help! I am going to take a look at it all this weekend. If the thermostats still work (testing them in hot water) but have some build up on them, can I clean them without damaging them?

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Check your thermoswitches also. They should not have continuity until about 185 degrees.  Then cooling off they should have continuity down to about 160-145 degrees then no continuity. The switch should close and sound horn around 185-190. 

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How do I check the thermostat switches?

I checked the poppet and thermostats and they were a lot cleaner than I expected. I tested the thermostats in hot water and they opened up. I’ll attach pictures so you can judge. I couldn’t reach the zip tie on the other end of the poppet hose to disconnect it though. Would the mushroom shape poppet be much of an upgrade over the old one?

 

668BBD46-21A5-4889-A729-615CA88FF888.jpeg

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D7147AD3-67B2-4A4F-8FF9-CCD0AB7B0517.jpeg

018A426F-779E-4782-8D9D-9BDCE878AE00.jpeg

9B13C8F3-9D06-4EC7-BF36-BDD89409F57C.jpeg

4CA127B6-9772-49FD-848E-7E6175928328.jpeg

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Clean out the water jackets, file them true and buy new gaskets. Be careful about breaking off bolts.   The good news is it is usually the head that spins off so you can use some vice scripts to get the remainder out after you remove the jackets. 

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5 hours ago, Desperado213 said:

How do I check the thermostat switches?

I checked the poppet and thermostats and they were a lot cleaner than I expected. I tested the thermostats in hot water and they opened up. I’ll attach pictures so you can judge. I couldn’t reach the zip tie on the other end of the poppet hose to disconnect it though. Would the mushroom shape poppet be much of an upgrade over the old one?

 

668BBD46-21A5-4889-A729-615CA88FF888.jpeg

747868C1-225F-4A11-95E0-B2496013561D.jpeg

D7147AD3-67B2-4A4F-8FF9-CCD0AB7B0517.jpeg

018A426F-779E-4782-8D9D-9BDCE878AE00.jpeg

9B13C8F3-9D06-4EC7-BF36-BDD89409F57C.jpeg

4CA127B6-9772-49FD-848E-7E6175928328.jpeg

For the price of a thermostat...I buy new ones.....not worth my time to figure out if the are working or not....if you clean on regular basis...then maybe....but, I just go the the Yamaha dealer and buy NEW OEM parts from my dealer.....no aftermarket for me when it comes to parts....

 

 

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35 minutes ago, Bout Time 1 said:

Disconnect the switches and place them in a pot of water and heat it up. You need a digital temp gun or thermometer to read the water temp. 

Where are they located? Do I need to just have the key to the on position or does the motor need to be running?

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They are at the top of the head. Its a small round plug that sits in a round detent with two wires and a plug. Unplug them and pull them out. They are not screwed in. Just press fit. They are black and about 1/2-3/4” across. Put just the switches in hot water not the wires. Check with a multimeter for continuity between the two terminals of the plug. If one is bad it will trip and put the boat in limp mode. 

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2 hours ago, Bout Time 1 said:

Here is the switch. 

 

FA57D5FF-C23B-4453-B4BF-6652D7F7E641.jpeg

Perfect! Thank you for the help, I will be checking these this weekend. The boat is in Panama City and I live in Tallahassee so I will have to check them this weekend. Do you think I should buy a new poppet and thermostats? I dont want to be spending money that doesnt need to be spent. The gaskets should probably be changed at a minimum. The thermostats cleaned up pretty well but may be worth getting new ones.

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I think I am going to try flushing the system with rydlyme before going the route of removing the heads. I will use the procedure as listed on this forum thread:

https://www.thehulltruth.com/boating-forum/540948-rydlyme-flush.html

My questions is they said they hooked the pump up to the water pick up tube, are they refering to the hose on the motor where you can hook up a garden hose or is there a tube that sticks down into the foot?

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On ‎2‎/‎5‎/‎2018 at 10:12 AM, Desperado213 said:

I think I am going to try flushing the system with rydlyme before going the route of removing the heads. I will use the procedure as listed on this forum thread:

https://www.thehulltruth.com/boating-forum/540948-rydlyme-flush.html

My questions is they said they hooked the pump up to the water pick up tube, are they refering to the hose on the motor where you can hook up a garden hose or is there a tube that sticks down into the foot?

He removed the lower unit.  He is referring to the water pickup tube in the mid section. 

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Well I flushed the motor today with rydlyme for 2.5 hours and when I went to install the thermostats it looked the exact same. Thats when I realized I didn’t have the poppet installed when I was flushing so the rydlyme wasn’t getting up into the thermostat area. The poppet cover was very clean though. So after kicking myself for that dumb mistake I installed the new poppet and flushed it again but this time I used barnacle buster diluted 1:3. This is when a lot of the junk build up came out of the motor. I reinstalled the thermostats and changed the gaskets. I took her for a quick spin and didn’t throw any alarms so I’m hoping it’s all good now!

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