marion_moore
Contributing Member
"I need some serious help, or
"I need some serious help, or maybe it is a simple fix and I just don’t know enough to repair it. Anyway…
Background: Back in November of 2008 I blew my DT115, purchased a ’97 DT140 with exterior corrosion issues. I placed the DT140 power head on the 115 engine holder. I noticed that the exhaust tube http://store.brownspoint.com/dt140/fig043-1408601.asp was a different part number but didn’t change it. That may not have anything to do with it over heating or may be the problem.
Symptom: Fishing on 6/8 the engine overheated above 3000 rpms. Temp alarm comes on and rev limiter is activated. Water temperature was around 82 deg and it was a 85 deg day. The first run of the day which was around 15 minutes it did not overheat. This is the warmest day yet after the power head swap. I have fished 3 other times when the weather was cooler with the same setup and no problem. The power head was too hot to hold your hand on it for more than 2 or 3 seconds. Tell tale water stream was fair to good and varied as the engine ran. This may have been when the thermostat cycled.
Repairs made: 6/12 I replaced the water pump impeller, gasket, and water pump plate. Old impeller was 100% intact. Back in April all water passages in the heads were scraped and cleaned. I did this when I swapped power heads while the exhaust cover and heads were removed and inspected. New head gasket and exhaust gasket properly torqued. I also changed the water pressure valve when the head was swapped http://store.brownspoint.com/dt140/fig001-1408601.asp . 6/12 flushed the engine from the thermostat port and have great flow. The gasket / rubber bushing on the water tube is new. I even slid it down a little so the water pump housing would push against it and have a good seal. I also noticed that I could cut steel with the tell tale while I have the water hose hooked to the flush attachment on the engine block (this is the later model direct connect for the hose, not muffs).
Symptom: Fishing 6/14 the engine overheated on the second run of the day at around 4000 rpms. Fished for an hour then trolled at 1000 rpms for 5 minutes. Fair tell tale. Ran at 4000 rpms for 2 or 3 minutes and the engine overheated. Got ticked, removed the thermostat. Ran at 4000 rpms for 2 or 3 minutes and overheated. Tell tale was fair. Decided to run wide open at 5500 rpms. Ran for 20 minutes back to the ramp without it overheating with the thermostat removed. I did not try to decrease to a cruising rpm of 4000 to see if it overheated again. I just wanted to get back.
Repairs made: 6/16 tested the thermostat per the shop manual. The thermostat did begin to open around 104 deg. It says nothing about how far it is supposed to open. Checked the spark plugs and thought I saw a milky substance on #4 plug. Inspected the piston head with a gun bore light and did not see a carbon free clean head or any milky look inside the bore. Checked compression and got 140 on all 4 cylinders.
Moving forward: I am stuck. Maybe it is the thermostat. I am also considering pulling the head and swapping the exhaust tubes. I could also replace the water pump case/housing but it looks good to me. I have another completely rebuilt lower unit that I thought about swapping as well just to see what might happen. I have read that a leaking head gasket could blow into the water passages and block the flow of water but with good compression readings is it worth buying or building a leak down tester?"
"I need some serious help, or maybe it is a simple fix and I just don’t know enough to repair it. Anyway…
Background: Back in November of 2008 I blew my DT115, purchased a ’97 DT140 with exterior corrosion issues. I placed the DT140 power head on the 115 engine holder. I noticed that the exhaust tube http://store.brownspoint.com/dt140/fig043-1408601.asp was a different part number but didn’t change it. That may not have anything to do with it over heating or may be the problem.
Symptom: Fishing on 6/8 the engine overheated above 3000 rpms. Temp alarm comes on and rev limiter is activated. Water temperature was around 82 deg and it was a 85 deg day. The first run of the day which was around 15 minutes it did not overheat. This is the warmest day yet after the power head swap. I have fished 3 other times when the weather was cooler with the same setup and no problem. The power head was too hot to hold your hand on it for more than 2 or 3 seconds. Tell tale water stream was fair to good and varied as the engine ran. This may have been when the thermostat cycled.
Repairs made: 6/12 I replaced the water pump impeller, gasket, and water pump plate. Old impeller was 100% intact. Back in April all water passages in the heads were scraped and cleaned. I did this when I swapped power heads while the exhaust cover and heads were removed and inspected. New head gasket and exhaust gasket properly torqued. I also changed the water pressure valve when the head was swapped http://store.brownspoint.com/dt140/fig001-1408601.asp . 6/12 flushed the engine from the thermostat port and have great flow. The gasket / rubber bushing on the water tube is new. I even slid it down a little so the water pump housing would push against it and have a good seal. I also noticed that I could cut steel with the tell tale while I have the water hose hooked to the flush attachment on the engine block (this is the later model direct connect for the hose, not muffs).
Symptom: Fishing 6/14 the engine overheated on the second run of the day at around 4000 rpms. Fished for an hour then trolled at 1000 rpms for 5 minutes. Fair tell tale. Ran at 4000 rpms for 2 or 3 minutes and the engine overheated. Got ticked, removed the thermostat. Ran at 4000 rpms for 2 or 3 minutes and overheated. Tell tale was fair. Decided to run wide open at 5500 rpms. Ran for 20 minutes back to the ramp without it overheating with the thermostat removed. I did not try to decrease to a cruising rpm of 4000 to see if it overheated again. I just wanted to get back.
Repairs made: 6/16 tested the thermostat per the shop manual. The thermostat did begin to open around 104 deg. It says nothing about how far it is supposed to open. Checked the spark plugs and thought I saw a milky substance on #4 plug. Inspected the piston head with a gun bore light and did not see a carbon free clean head or any milky look inside the bore. Checked compression and got 140 on all 4 cylinders.
Moving forward: I am stuck. Maybe it is the thermostat. I am also considering pulling the head and swapping the exhaust tubes. I could also replace the water pump case/housing but it looks good to me. I have another completely rebuilt lower unit that I thought about swapping as well just to see what might happen. I have read that a leaking head gasket could blow into the water passages and block the flow of water but with good compression readings is it worth buying or building a leak down tester?"