Overheat (poppit valve)

[imjus4u2nv]

My engine overheated when I started it up for the season (s150txru) and have worked on a few things since then (see other posts where the pros bailed me out. Water pump and driveshaft bushing replaced as it was beat). Should also mention the rpms seems a little high at around 10k after settling.

Still overheating - I checked the heads(as suggested) and the starboard side top was very hot after overheat.
The telltale seems weaker then usual the more I think about it (but about same as before I did the waterpump this week).
I checked out the poppot valve and will order parts to replace as cheap to do. Here are some pics. Not really sure how poppit valve works and how would cause an overheat at low rpm can someone educate me? I can guess that the valve is stuck closed as it did not just come out (had to pull out with pliers).
I will pull plugs tomorrow and take a look also.

 

[seasick]

The motor may overheat at low revs if the poppet valve is stuck OPEN. If one side of your motor is running hot, it's not the poppet valve. That would affect both heads.
First thing to do is pull the t-state on the hot bank and inspect the housing and water channels for blockage. Take the t-state and put it in a pot of water on the stove and heat the water. Use a thermometer to measure the water temps. As you approach 140 or 150 the t-stat should start to open. By 160 or so, it should be pretty much open. If you don't know what a good t-stat looks like when open or how fast it opens when heated, pull both t-stats and cook both so that you can compare them to each other. ( I usually water test new t-stats also . Every now and then you get a bad new one.)
What if the t-stats are OK but one head is still running too hot?
Pull the plugs on that bank noting which is which and look at them. They should all look about the same color and not be excessively wet or burnt. If you recently replaced the plugs, the inspection may not tell you much.

There are a few things that can cause overheating; bad t-stat, low water flow, too lean a mixture, poor or no-oil in gas mixture ( damage to cylinder walls, exhaust leaking into cooling water and a few other not so common things.

One thing I have noticed from many of your pictures is the corrosion and crud buildup in water passages. Hopefully that's the problem as opposed to corrosion that has eaten through a water passage.

 

[HMBJack]

I second Seasick's suggestion to look at the Thermostats. Remove, test and clean them up. Use a pipe brush to clean the Thermostat housing. I do this annually now as even with regular FW flushing, they seem to collect a bit of crap in that area (on the 3.3L V6's at least).

 

[SkunkBoat]

are you on earmuffs or in a yamaha hot tub? My yammies would usually overheat on earmuffs.

try taping the drain holes.

also save time....just pull t stats and run. if it doesn't overheat, put new ones in.

my experience with T stats is that, unless they are clogged with salt goo, they only fail open.

 

[seasick]

are you on earmuffs or in a yamaha hot tub? My yammies would usually overheat on earmuffs.

try taping the drain holes.

also save time....just pull t stats and run. if it doesn't overheat, put new ones in.

my experience with T stats is that, unless they are clogged with salt goo, they only fail open.

Although that motor may overheat on muffs if the water volume is low, both heads will heat up. The original post states that one side is overheating. I don't doubt your experiences but in my case those Yami stats will often not open all the way or will stick until the temps get high and then sort of pop open. Of course that is just my observations on my SX150 motor

 

[SkunkBoat]

Although that motor may overheat on muffs if the water volume is low, both heads will heat up. The original post states that one side is overheating. I don't doubt your experiences but in my case those Yami stats will often not open all the way or will stick until the temps get high and then sort of pop open. Of course that is just my observations on my SX150 motor

The fail open experience was twice on a Zuke 140. I think they are designed to stick open if an overheat condition happens. I think probably it happened due to eel grass clogging the inlets and giving me a high temp error. I cleared the grass and everything was "fine". The next spring I was doing maintenance and found the t stat popped open. That happened in two different years. I think now you are supposed to replace T stats every time after an overtemp condition. These were the only times I could definitively say the T stat was bad.

I have done the "boiled t stat " test a few times before (I know, don't really boil) and it has never told me anything. I just ended up replacing them anyways.
I think the salt goo is often the problem. If it blocks the bypass you get an airlock and maybe water never reaches the T stat.

 

[imjus4u2nv]

Just reading this now, and did what you suggested this morning. One side was definitely hot (couldnt keep hand on) and other side warm to touch.
Thermostats were just replaced end of last season, checked and it looked and operated fine (used the pot of water method and saw it open and close).
Checked the spark plugs, they all looked good. Checked compression, all good and equal at 112 to 115 psi.
I am pretty sure poppit was stuck shit bit certainly need to be replaced.
Once i get that part I will head down to the dock and start in water (I start on earmiff and in a tank of water that just barely covers the intake for waterpump which is why I use the muffs to).
A blockage seems likely - wondering if the missing washer from the lower unit could work it's way in somewhere. What is best way to get the goo out or check for blockages.

 

[SkunkBoat]

Once i get that part I will head down to the dock and start in water (I start on earmiff and in a tank of water that just barely covers the intake for waterpump which is why I use the muffs to).

With any luck it'll run fine with boat in the water.
If the water in your tub isn't high enough, water drains out of holes in lower unit and you never get enough pressure.
I did have some success by taping over holes while on muffs, if the boat wasn't 100yds from the house

 

[seasick]

The only way I have found to see if the water is getting to the t-stat is to remove the t-stat and cover and start the engine on muffs. Water should spurt out pretty quickly. Don't run more than like 10 seconds.
Now put the t-stat back together and try the other bank for a cpmparison.

 

[seasick]

The fail open experience was twice on a Zuke 140. I think they are designed to stick open if an overheat condition happens. I think probably it happened due to eel grass clogging the inlets and giving me a high temp error. I cleared the grass and everything was "fine". The next spring I was doing maintenance and found the t stat popped open. That happened in two different years. I think now you are supposed to replace T stats every time after an overtemp condition. These were the only times I could definitively say the T stat was bad.

I have done the "boiled t stat " test a few times before (I know, don't really boil) and it has never told me anything. I just ended up replacing them anyways.
I think the salt goo is often the problem. If it blocks the bypass you get an airlock and maybe water never reaches the T stat.

That's interesting about zuke stats opening if overheated. I can see how that might be designed into them. If things get too hot, there may be some sort of fusible link that disconnects the retracting spring allowing the stat to open. The Yami stats don't work that way to my knowledge.

 

[imjus4u2nv]

Issue (non issue) fixed!!!!
First thank you! Second sorry for being an idiot.
I took the boat down to the dock she started right up, dropped down to 700 rpms, and did not overheat. I gave a little throttle and the telltale was soo strong and super strong at idle. Not sure if had a clog or bad water pressure but running like she should. Assume it was water pressure, will check with better hose tomorrow and see I can get it to run in the driveway again without overheating.
Hioing I will be out self quarantining Saturday fishing for some spring tog! Ft.
Thanks again fellas, less on learned the hard way.
But, when rinsing engine through the hose connection, should water be coming from all these spots (I cant remember but looks like water coming out towards tbe front where shiftshaft is) does that seem normal? I plan to drop lower unit and reseat the pump - seems odd how copper pipe goes into the water pump ( has small black grommet but dont seem like a great seal).

 

[leeccoll]

Hey imjus4u2nv,

I have had overheat alarms before when using ear muffs. Depends on water pressure in your area. For this reason, I only use the static hose connection. I have a Honda BF200, but water does come out everywhere. Looks normal to me bud!

Glad your mystery is solved!!

Lee

 

[imjus4u2nv]

Still wondering why when it overheated was just one side that was hot (may be air lock or water not getting to that side).

 

[seasick]

Still wondering why when it overheated was just one side that was hot (may be air lock or water not getting to that side).

The water streams are OK.
Regarding one side getting hot: Was the motor tilted up a tad and turned to one side?
Whatever, the overheating doesn't necessarily mean that water wasn't up that side. It just wasn't enough water flow to effectively cool especially when the other side t-stat opened.

 

[imjus4u2nv]

The water streams are OK.
Regarding one side getting hot: Was the motor tilted up a tad and turned to one side?
Whatever, the overheating doesn't necessarily mean that water wasn't up that side. It just wasn't enough water flow to effectively cool especially when the other side t-stat opened.

Engine was straight up and down and dead center, ordered a digital thermometer and will check head temps again once running.
I guess was trying to following the water from static washdown intake to the lower unit, and was trying to figure how water is coming out by the shiftshaft "should" stay in sealed pump and only way out is connection between the pump and the copper pipe to engine (bad seal) or the driveshaft (maybe not supposed to be sealed). Not even sure how water comes out the intake - shouldn't the impeller block that?
I plan to sail on sunday and will stay close to the dock for a little.

 

[seasick]

The pump is not sealed at the drive shaft, it has washers and a cap but it can leak. In general no big deal. The leak will be greater if the washers, bushing and cap were tapped down but the drive shaft wasn't pulled up to reduce the up/down play.
Point two; If you replaced the plastic pump housing you have a new lower seal on the water tube. The upper seal is hard to get to and may leak a little but that's no big deal either.
Finally, the impeller doesn't block anything. When not moving water can flow in or out. Only when spinning does centripetal force propel the water.
I know you are probably a bit stir crazy but stop looking for problems that aren't there

 

[seasick]

I just looked at the earlier photos. The plugs look wetter than I would like to see. Actually the color of the porcelain is a better indicator of issues and yours are not the nice dry and tan condition that is optimal. That can be due to a lot of things, one being just not running long enough to sufficiently warm up everything. Nevertheless I suggest that you first check the'precision oilier system' more commonly known as the oil pump linkage adjustment. You may be mixing in a bit more oil than needed. If that is OK and after some real usage, you may want to check the O2 sensor. I do not normally say that since it is easy to damage a very expensive part and it is not an issue a lot more often than it is.
If the O2 sensor is not working correctly, just about all of the time it will cause the engine to run rich. That can result in wet or carbon fouled plugs and maybe more smoke than usual. Of course, too much oil has the same symptoms ( OK , yes the smoke in theory should be a different color)

Also if you have a plug out again, measure the gap, it looks wide but that may just be the photo

What model is the sparkplug? What model year motor?

 

[imjus4u2nv]

The pump is not sealed at the drive shaft, it has washers and a cap but it can leak. In general no big deal. The leak will be grater if the washers, bushing and cap were tapped down but the drive shaft wasn't pulled up to reduce the up/down play.
Point two; If you replaced the plastic pump housing you have a new lower seal on the water tube. The upper seal is hard to get to and may leak a little but that's no big deal either.
Finally, the impeller doesn't block anything. When not moving water can flow in or out. Only when spinning does centripetal force propel the water.
I know you are probably a bit stir crazy but stop looking for problems that aren't there

Thank you, was exactly the info I was looking for!

 

[imjus4u2nv]

I just looked at the earlier photos. The plugs look wetter than I would like to see. Actually the color of the porcelain is a better indicator of issues and yours are not the nice dry and tan condition that is optimal. That can be due to a lot of things, one being just not running long enough to sufficiently warm up everything. Nevertheless I suggest that you first check the'precision oilier system' more commonly known as the oil pump linkage adjustment. You may be mixing in a bit more oil than needed. If that is OK and after some real usage, you may want to check the O2 sensor. I do not normally say that since it is easy to damage a very expensive part and it is not an issue a lot more often than it is.
If the O2 sensor is not working correctly, just about all of the time it will cause the engine to run rich. That can result in wet or carbon fouled plugs and maybe more smoke than usual. Of course, too much oil has the same symptoms ( OK , yes the smoke in theory should be a different color)

Also if you have a plug out again, measure the gap, it looks wide but that may just be the photo

What model is the sparkplug? What model year motor?

The plugs only have about 5 minutes on them this season in the picture, not sure of that makes a difference or if they would have burned clean already (fogged and sea foamed end of the season). Plugs were replaced last season and gapped (will recheck when I pull them after putting some hours on it Sunday).
It is a 1996 s150txru. I felt she was smoking more at the end of last season but think it was just the cold and humid mornings (but did she tend to blow a little smoke on startup which lends to your running rich theory) but At the dock the other day she didnt smoke really all. Running Ngk plugs (same kind as inside the cowling says and same as previous owner used). I did check the oil linkage and all looked fine, decided not to mess with it as rich is safe.

 

[Fishtales]

might want to run it in a tub with some vinegar to work out salt deposits. you'd be amazed how much is in the motor. agree on the tstats. I change em every 3 years. never had an issue.