150 TXRA overheating

[cheetah chrome]

After getting all of my fuel issues sorted out I am now overheating on the muffs after 10 or so minutes at a little above idle. I shut the motor down immediately after alarming and ohm'ed out the alarm sensors and both were closed...and eventually opened as the motor cooled. Specifics on the motor below any insights appreciated.

Strong tell tale (but cool)
New impeller/can kit never run dry
New poppet mushroom style
New tstats
Both over temp alarm switches test to be in spec w manual
Motor has been used in salt water and flushed after each use in my ownership
I didn't take laser thermometer readings this time but did earlier in the week and saw one head was ~10F warmer than the other (135 and 145) if I remember correctly.

I've read about putting some 'grease' on the alarm switches to ensure you are getting a good thermal bridge to the head. What type of grease do you use? 2-4-C? Dielectric? Hoping for a false alarm but fearing worse.

Any thought on where to check next?

[rodbolt17]

use dielectric grease.
but that's not the problem.
could be your water pressure to the muffs is to low.
15 min is an awful long time to run a V6 on a set of muffs.

[boscoe99]

As noted, not uncommon for a Yam to over temp when being flushed on hose muffs. My F200 would do it.

If the motor runs fine in the water you do not have a problem.

[cheetah chrome]

Update:
It was definitely water pressure. My place is on a well and just wasn't pushing enough down the hose to keep up. I switched over to 55 gallon drum today and no over temp alarms during a couple of flush cycles (once w vinegar, once a lil' dawn, then finally just water). I took head temps each run say after 10 mins.

First - 134F; 131F
Second - 130F; 154F
Third - 132F; 132F

After the second run, concerned w the different temps, I pulled both Tstats and tested them in a pot of water. Both test out fine per the manual. I didn't see any sand or shells that would prevent movement but I blew them out w compressed air regardless. I'm not exactly sure what the cause of the different head temps was but the final run head temps we exactly the same.

Other items I did today was pop out the over temp switches and put a dollop of dielectric grease on them, pulled poppet valve to check for any garbage there (all was fine....mushroom seats perfectly on the bushing).

One thing I did notice which I am not sure if it is an issue or not: is it normal to see cooling water spritzing out of the exhaust ports below the cowling?

[cheetah chrome]

Here's some pics of the solids at the bottom of the drum after the first round.

[cheetah chrome]

Picture two

[99yam40]

One thing I did notice which I am not sure if it is an issue or not: is it normal to see cooling water spritzing out of the exhaust ports below the cowling?

Most have some water come out with the exhaust at the idle relief ports

[cheetah chrome]

Great thanks! I think cooling wise I was looking for a problem that wasn't necessarily there. The low flow at the muffs put me down a rabbit hole....now onto getting the motor to idle perfect and then it's sea trial time.

[TownsendsFJR1300]

Here's some pics of the solids at the bottom of the drum after the first round.

All that sand / crap come out after flushing in the tank? Mostly sand, or?


If it is sand, you may want to pop off the LU screens on each side of the lower unit and cheak for any crap in there....

[cheetah chrome]

All that sand / crap come out after flushing in the tank? Mostly sand, or?


If it is sand, you may want to pop off the LU screens on each side of the lower unit and cheak for any crap in there....

Yup, we have somewhat course sand up here...but that is just what it is. The pics above were after the first flush. I pressure washed the drum between runs to remove all of the acid from the vinegar and sand. It was ~50% less sand on the second run and very little on the third. I was actually trying to get salt deposits out of the motor. Judging from the cloudy, suspended particles in the first two runs I think I managed to get out some of the easy/dissolvable salt.

I cleaned the screens and blew out lower unit passages when I changed the pump (0 hours in saltwater since...till this weekend hopefully).

Thanks again,

[TownsendsFJR1300]

Good luck with the sea run..

Just an FYI, a couple of links re cleaning salt out of the engine should it be needed;

http://www.yamahaoutboardparts.com/f...g-th19434.html


http://www.yamahaoutboardparts.com/f...m-th23666.html

[cheetah chrome]

Update:
Ran boat for 1.5 hours today. Everything went well until I throttled up over 4200 RPM and I would get an over temp alarm. Reduced RPM and ran flawless for the rest of the time. Reading a bunch of threads it sounds like salt build up is the typical culprit for this type of over heating. Are there any other possible causes for high RPM overheating? The reason I ask is previous owner (my father) says he has a receipt where the heads were pulled by a yamaha certified tech less than 10 operating hours to get build up cleaned out.

Just to recap:
New pump kit (impeller, base, cap)
New poppet (pulled verified it is clean, seats properly)
New TStats (tested fine per manual)
Pisses like a race horse

Would a bad connection at the top of the water tube from the pump cause this issue? I've read a few threads where people have found that bushing/seal was damaged.

[TownsendsFJR1300]

That's exactly what my neighbors 200 was doing until we pulled the heads and cleaned out a WHOLE bunch of salt build up at the lower 2 cylinders (about 95% clogged).

And that procedure was supposedly done 10 hours ago? Does it appear the heads were actually pulled or perhaps just the covers to the head?

Do you have access to a lazer temp gun?

[cheetah chrome]

10 hours is max since the work, that I am certain of. Father stored the boat after the work was done and it came into my possession after that where it sat for a couple of years. Now whether or not the tech actually pulled the heads or just charged him for the gaskets is another story. I attached the line items from the receipt....labour certainly seems low to pull some heads, clean passages, reassemble but maybe not if you do it all the time and don't snap all the bolts.

I do have access to a laser temp thermometer.

[TownsendsFJR1300]

Says he pulled the head and cleaned them.

I have to assume he cleaned the water jackets around the cylinders, that's where we found most of the salt build up. There was a good amount of salt in the head but the block was by far the worst(easily 95% clogged). However its not on the bill, ??(probably part of the head cleaning)

About a year ago, my neighbor was quoted a price of $800 for his 200 HP so your price is in line.

With your lazer gun, I'd put the boat in the water (or tank) warm it up and check for hot spots near the sensors. (The sensors on my neighbors engine was right where all the salt build up was)...

You may have to run the boat up to speed and when it goes into limp mode check again with the gun. If its that bad, it may very show several hot spots, especially towards the bottom cylinders.

(Make sure your shooting at the same area on each cylinder head to be accurate).

**Actually, shooting at the cylinder wall just below when the head mates would likely be more accurate to get an idea of temps..
Good luck..