Could these little salt dams (pics) in the head really cause weak, hot telltale?

[pcrussell50]

So when I dropped a new (to me) 2.4/200 powerhead onto a known good mid/lower, I got a weak, hot telltale. No overheat buzzer though, and I tested it. Compression and leak down are both good because I tested those before I removed the heads.

When I removed the heads, I found these salt dams outside the sides of the chambers:
link: https://postimg.cc/cKBy6c9n





Looking for a sanity check: I cleared away the salt dams, but before I put the heads back on, it occurs to me to wonder if those little salt dams could really be cause of a weak, hot telltale? Again, with NO overheat buzzer.

Somehow my visualization of the flow situation is brain farting and I'm not seeing something right.

-Peter

[rock]

Can't imagine it would but clearing them out has to help.

Rock

[pcrussell50]

Can't imagine it would but clearing them out has to help.

Rock

That leaves me at a loss as to the low flowing weak and hot telltale, without overheat buzzer.

Maybe it's time to pull the water pump, but it was raging good last year and hasn't been used since.

-Peter

[rock]

Impellers usually fail first time out cuz the vanes have taken a set over winter. Other way to explain is one vane is bent almost 90 degrees and has sat that way over the winter and sometimes they either break off or just don't reach the cup wall therefore cavitating.

Rock

[sonicss33]

On this you are being way too analytical, replace the water pump and accept the win. BTDT.

[25two.stroke]

How hot is hot? They pee hot with thermostats. They pee 143 deg. That's hot to the touch. Same with the heads. What is the temp number as read with a laser thermometer?

[skialot2]

Telltale hoses are connected to the thermostat housings. The water should come out hot. Just not burning hot. My 1992 135 has a weak telltale also. But it has 15 psi at speed. Temp stays around 140, slightly hotter when idling. I just bought a 1989 race modified 150. Usually has a very powerful telltale. water shoots around 10 feet away. Temp stays at 140 all the time. Twice already the telltale spout has gotten clogged with salt and turned into a weak stream. But the motor still did not get hot. I had to push a small drill bit through the spout a few times with the motor running to clear the clog. Check yours to see if it's just clogged.

[pcrussell50]

Burning scalding hot. Steaming even.

We don’t get much in the way of winters in Southern Nevada. 50’s for a high on the coldest days. And I’ve been maintaining this family of Merc V6’s for about ten years now. If I replace an impeller after three years, it still looks good but I do it anyway.

And water veritably gushes out the thermostat openings when I have the lower off and a garden hose tight on the brass tube.

===

I will of course check the water pump anyway because of the odd chance that the impeller grenaded anyway.

BUT

I wonder if I dorked something up in getting the copper tube attached to the water pump when I was stabbing the LU up into place? There is a white, hard plastic tube sticking out the top of the pump housing about 3-4 inches that I slid the copper pickup into. And I wonder if something went wrong there?

OR

Since this was a powerhead swap from a 2.0 to a 2.4, I wonder if I got something wrong in the adapter-exhaust plate stack and fitting the copper tube to it? Something where a garden hose has enough flow to fly out the thermostat openings in the top of the head, but not the impeller?

-Peter

[Dave S]

Check poppet valve.......if not opening H20 can't do it's job.....

[pcrussell50]

Check poppet valve.......if not opening H20 can't do it's job.....

Is there really enough pressure to push open the poppet spring at 700 rpm idle on the muffs? I thought (and could easily be wrong), that the poppet was supposed to open at like 3000-3500 rpm.

===

Also, I've had my poppet off twice in the last month diagnosing and fixing a weep out the vent hole, which I did with a new diaphragm. I think I have it right. It's the two-chamber poppet design that has the 90 degree barb and hose that runs up to the top of the block where the fitting for the water pressure gauge goes. When I'm idling this motor and it's hot, almost nothing comes out the 90 degree barb

Sounds like I need to know more about this cooling system. :-/

-Peter

[Chaz]

Peter,
Looking at the first picture .. yes on both side of the combustion chamber there is a lot of build-up in the water channels .
I had two sets of Yamaha heads that had the same issues. I bead blasted the heads and then epoxy primed the water jackets.

And yes replacing the water pump is a good idea. If nothing else, slip the cover off and take a peak at it ... all the vanes in place and pliable, with no tares .. send it ..

Also for the two chambers shown, it looks as if the piston's for those two holes have dinked the head on the right side. See if the piston's have the same witness marks. If nothing else, it might be so close it won't grow carbon there ..

[Jim Speros]

On this you are being way too analytical, replace the water pump and accept the win. BTDT.

Manual states inspect impeller every year replace every other. Service the water pump. If base under plate has any sign of melting replace it. Make sure the silicone strip is on exhaust divider near water pump. Make sure grommets of both ends of water tube are intact. If it has 15 lbs running, it pees from telltail off idle and no alarm is sounding on tested alarm sender MOVE ON.

[Jim Speros]

Pretty sure the salt dam you speak of is just because of gasket. Something has got to hold the squish ring in position. On jug side is open water passage. I can't say it isn't a good idea to clean it out to prevent decay and future issues but on its own IMO it is a non issue.

[Dave S]

The dammms...... they cause the gasket to deform when salt builds up.......cut them out/away.

[pcrussell50]

OK guys, loud and clear on the water pump. Everything certainly points towards that being suspicious, so you don't have to twist my arm to check it. However based on experience, I will be flabbergasted if it's not pliable, with all vanes, and no tears, and not taken much of a set. But I also hope to be wrong, because it will point to an easy fix if there is a problem.

DaveS, this motor will never see salt again, so that chapter is behind me. ;-)

Manual states inspect impeller every year replace every other. Service the water pump. If base under plate has any sign of melting replace it. Make sure the silicone strip is on exhaust divider near water pump. Make sure grommets of both ends of water tube are intact. If it has 15 lbs running, it pees from telltail off idle and no alarm is sounding on tested alarm sender MOVE ON.

Great reminder of the fundamentals Jim, thank you. Will do. I’m not sure at all that the lower water tube grommet survived the move. When I stabbed in this LU a few days ago, I didn’t even look to see if the lower grommet was even there. I’ll go through the whole pump per your guidance in a few days when I get back. The buzzer has never gone off in this drama even though the weak telltale was scalding hot and had faint wisps of steam. I have tested the circuit by grounding, AND I continuity tested the sensor before and after heating it. It has continuity when hot.

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Oh yeah… Someone said a few posts ago about checking the poppet (which in fact is freshly rebuilt and verified unobstructed), but… At 700rpm at idle is that enough to overcome the spring and press it open?

-Peter