boatmon345
Petty Officer 2nd Class
- Joined
- Apr 26, 2006
- Messages
- 113
Back in 2006 I personally rebuilt my 1997 Yamaha 150 2-stroke, the first and only engine rebuild I had ever done. The reason for the rebuild was that it had thrown a rod due to bearing failure due to longterm saltwater intrusion in the crankcase due to a hole that developed in the block. I had a marine machinist straighten out the block (welded the hole, bored out the 1 cylinder that had been scored, machined the heads and block mating surface). I also cleaned all the passages with a wire brush. I applied a coat of Rustoleum rusty metal primer to the inner water passages, as that is what I believed at the time would be beneficial to protect the motor.
Since then we used the boat week after week for years (salt/brackish water) until we really started slowing down in 2013. There were very few problems with the motor except for an overheat issue which began in 2012 and is still a problem. Here is an excerpt from a log I keep on the motor:
6/2/12
Found water leaking from disintegrating exhaust manifold water valve housing. On 6/3, I decided to cap off both sides due to it being seized anyway.
6/30/12
Fishing / beach w/the dogs
*Found that engine overheats and reduces its power after running at 4300RPM or higher. Need to troubleshoot.
7/14/12
Replaced thermostats & gaskets with Sierra brand (50C).
Let gaskets dry overnight, then ran eng in neutral at 1500RPM for about 20 min. A droplet of water formed on the starboard top of water jacket. Wiped it away and it didn't come back. All looks well for a test under load.
7/28/12
Canal and river run.
Tested at WOT in river to see if overheat alarm sounded since thermostat repair: No alarm; overheat problem is solved.
6/23/13
Fishing to Span A with LV
-Engine overheated at WOT again.
6/29/13
Took apart thermostat housings and found the passages blocked with gook again (after only 11 months). Cleaned it all up, coated the surfaces with Rustoleum Rusty Metal Primer, tested the thermostats, and put back together using Permatex Ultra Blue as gasket instead of preformed ones. (Tested repair by running engine on 6/30. No leaks. Seems to be a good repair.)
7/1/13
-Replaced ignition key switch
-Flushed using earmuffs for the first time, but engine overheated.
7/5/13
Night fishing in river targeting snook lights.
-Took boat to WOT several times and it didn't overheat. The thermostat passage cleaning fixed the problem.
10/12/13 SAT
Boating in afternoon.
-Took to WOT (5000RPM) and overheated after about 30sec.
-Later, took to about 4200RPM and overheated a little bit later.
5/25/14
Boating
(no mention of overheating).
3/12/15
River boating at night.
*Engine overheats now at sustained 3800 RPM after a few minutes.
*Need to pull the thermostats out, clean the passages, and possibly remove them all together. As I bet they are caked with gook. The last time the thermostats were cleaned was 6/2013 which is almost 2 years ago.
3/13/15
Removed the thermostat housings, removed thermostats, wirebrushed all passages and surfaces. Used blue RTV silicon & reassembled, leaving thermostats OUT.
3/15/15
Took boat for test in river: It seemed to be able to sustain 3800RPM but by 4200RPM sustained it does overheat.
(Please, no flaming for some of the unorthodox things I've done).
After every outing I've always flushed the motor with the hose attachment, which I understand is not the best way to flush. I always run the motor once or twice a month when not in use, and flush it the same. I thought flushing with the hose attachment would be sufficient though. I have never changed the impeller, and I purchased the boat used in 2004. The telltale has always been very strong when the engine is above 1500RPM and moderately strong below 1500RPM, so I assume the impeller has always been doing its job.
(I know I know, a lot of guys recommend changing the impeller every year. I don't see why I need to do that if the telltale is strong, but let's save that debate for another thread.)
The several times I have pulled the thermostat housing, including the most recent, I have noticed white caked gook blocking some of the passages:
Click here for full size image.
Click here for full size image.
I reached my finger in and noticed a white jelly-type substance. I cleaned all this out before reassembling the thermostat housing but I suspect the cylinder waterjackets and drains are gunked up also. I "tasted" yes tasted the gook to see if it was salty but it is not salty at all. I don't know what it is, or why it is building up in my motor.
I am trying to avoid the hassle of pulling the heads off.
I read about using vinegar in a garbage can to circulate through the engine. Also read about RydLyme Marine which is apparently diluted hydrochloric acid (yikes!) that can be run through the engine to dissolve buildup. Here's where I read this.
Anyway, is there a proven safe & effective chemical treatment I can use to presumably unclog my 97 Yamaha 150 2stroke aluminum engine, or is taking off the heads pretty much a given at this point?
My friend's father-in-law has the same model Yamaha and he tells me that they had to have the heads pulled to remove what appeared to be "sand" in the lower part of the water passages.
Is there something else that I am missing?
Since then we used the boat week after week for years (salt/brackish water) until we really started slowing down in 2013. There were very few problems with the motor except for an overheat issue which began in 2012 and is still a problem. Here is an excerpt from a log I keep on the motor:
6/2/12
Found water leaking from disintegrating exhaust manifold water valve housing. On 6/3, I decided to cap off both sides due to it being seized anyway.
6/30/12
Fishing / beach w/the dogs
*Found that engine overheats and reduces its power after running at 4300RPM or higher. Need to troubleshoot.
7/14/12
Replaced thermostats & gaskets with Sierra brand (50C).
Let gaskets dry overnight, then ran eng in neutral at 1500RPM for about 20 min. A droplet of water formed on the starboard top of water jacket. Wiped it away and it didn't come back. All looks well for a test under load.
7/28/12
Canal and river run.
Tested at WOT in river to see if overheat alarm sounded since thermostat repair: No alarm; overheat problem is solved.
6/23/13
Fishing to Span A with LV
-Engine overheated at WOT again.
6/29/13
Took apart thermostat housings and found the passages blocked with gook again (after only 11 months). Cleaned it all up, coated the surfaces with Rustoleum Rusty Metal Primer, tested the thermostats, and put back together using Permatex Ultra Blue as gasket instead of preformed ones. (Tested repair by running engine on 6/30. No leaks. Seems to be a good repair.)
7/1/13
-Replaced ignition key switch
-Flushed using earmuffs for the first time, but engine overheated.
7/5/13
Night fishing in river targeting snook lights.
-Took boat to WOT several times and it didn't overheat. The thermostat passage cleaning fixed the problem.
10/12/13 SAT
Boating in afternoon.
-Took to WOT (5000RPM) and overheated after about 30sec.
-Later, took to about 4200RPM and overheated a little bit later.
5/25/14
Boating
(no mention of overheating).
3/12/15
River boating at night.
*Engine overheats now at sustained 3800 RPM after a few minutes.
*Need to pull the thermostats out, clean the passages, and possibly remove them all together. As I bet they are caked with gook. The last time the thermostats were cleaned was 6/2013 which is almost 2 years ago.
3/13/15
Removed the thermostat housings, removed thermostats, wirebrushed all passages and surfaces. Used blue RTV silicon & reassembled, leaving thermostats OUT.
3/15/15
Took boat for test in river: It seemed to be able to sustain 3800RPM but by 4200RPM sustained it does overheat.
(Please, no flaming for some of the unorthodox things I've done).
After every outing I've always flushed the motor with the hose attachment, which I understand is not the best way to flush. I always run the motor once or twice a month when not in use, and flush it the same. I thought flushing with the hose attachment would be sufficient though. I have never changed the impeller, and I purchased the boat used in 2004. The telltale has always been very strong when the engine is above 1500RPM and moderately strong below 1500RPM, so I assume the impeller has always been doing its job.
(I know I know, a lot of guys recommend changing the impeller every year. I don't see why I need to do that if the telltale is strong, but let's save that debate for another thread.)
The several times I have pulled the thermostat housing, including the most recent, I have noticed white caked gook blocking some of the passages:
Click here for full size image.
Click here for full size image.
I reached my finger in and noticed a white jelly-type substance. I cleaned all this out before reassembling the thermostat housing but I suspect the cylinder waterjackets and drains are gunked up also. I "tasted" yes tasted the gook to see if it was salty but it is not salty at all. I don't know what it is, or why it is building up in my motor.
I am trying to avoid the hassle of pulling the heads off.
I read about using vinegar in a garbage can to circulate through the engine. Also read about RydLyme Marine which is apparently diluted hydrochloric acid (yikes!) that can be run through the engine to dissolve buildup. Here's where I read this.
Anyway, is there a proven safe & effective chemical treatment I can use to presumably unclog my 97 Yamaha 150 2stroke aluminum engine, or is taking off the heads pretty much a given at this point?
My friend's father-in-law has the same model Yamaha and he tells me that they had to have the heads pulled to remove what appeared to be "sand" in the lower part of the water passages.
Is there something else that I am missing?
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