Ran Aground Issue - Tstats

Katemma Life

Member
Oct 7, 2018
135
cape cod
Boat Info
2007 sea ray 290 SLX
Engines
Twin mercruiser MAG 350 MPI w/ Bravo III
Was boating on an inlet area and ran onto a sandbar. I tried to power out of it and sucked up sand / mud into the drives. High-temp alarm shut one engine down and I limped home on the other.

After a few hours the engines both started and worked. The boat operates fine now except the Tstats were stuck open. This past weekend I replaced both Tstats successfully. I went out and ran the boat hard - it runs great; 4000 RPM for a good 15 minutes. Now one of the Tsats is back to being stuck open.

My question is, if I clean out the Tstat again, how long before the sand I sucked in stops clogging things up? Anyone else dealt with this issue?
 
Have you cleaned out your water pump(s) and replaced the impeller(s)? You probably have sand crammed inside the pump.
 
Most times powering off a bar can fill a block and manifolds with sand. How do you know the Tstat is open. Cant read the temp without water in there.
 
Most times powering off a bar can fill a block and manifolds with sand. How do you know the Tstat is open. Cant read the temp without water in there.
It just takes one grain of sand stuck in there opening the T stat Just a crack, to keep the temperature constantly down around 130. I know this from experience as a professional unintentional sand bar seeker.
 
If your engines are raw water cooled you probably filled the engine blocks with sand and may need to have the core plugs removed (big job) in order to flush out all of the sand. You may looking at an insurance claim.
 
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If your engines are raw water cooled you probably filled the engine blocks with sand and may need to have the core plugs removed (big job) in order to flush out all of the sand. You may looking at an insurance claim.
 
It just takes one grain of sand stuck in there opening the T stat Just a crack, to keep the temperature constantly down around 130. I know this from experience as a professional unintentional sand bar seeker.
This exactly. So you need to go WOT to get the t-stat to open a bit further so the sand can pass through or take it out completely for a day or 2 for a good flush
 
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What would be the harm in pulling the T stat out let it sit at a idle and warm up then take it out for a run.
 
Thanks for the feedback. I am most concerned with the reply about "filling the engine block with sand"

Does that make sense considering that I've run the boat several times without issues (other than tstat opening) since the incident?

I am aware that its isnt over heating cause I ran it at 4000 rpm for 20 minutes. The temp guage right after replacing the Tstats was at 160 and good but then went down to 100 and has stayed there (100 is pegged at the bottom)

Question: if I replace the impellers should I go ahead and replace the pumps all together as well?

THANKS for your replies!!!
 
We know you pulled at least some sand into the cooling system. Can't be too much because engines are still running cool. If it were my boat (assuming it is raw water cooled) I would:
  • Pull the blue drain plugs on the block and manifolds and see if any sand comes out with the water. If there is a lot of sand try cleaning it out with a wire, you might need to repeat this a few times by running the engine, then pulling the plugs again.
  • Pull the thermostats and go for a ride with the thermostats out - won't hurt anything for a little while.
  • If above is successful, then monitor the engine temps - no need to go changing pumps and impellers yet. You probably shortened the life of the impellers, but you didn't ruin them. Change them at the first sign of any cooling issues - if you can't lay your hand on the risers because they are too hot, then it's time to change the impellers. Inspect / change the pump housings at that time.
  • Last, pull the hoses from the oil / PS cooler, you probably have some debris stuck in there also.
It's possible you pulled in a lot of sand and packed things full (and that would be a big problem), but I don't think the engines would be cooling properly.
 
Thank you BillK
One last question - one a standard basis, how often would someone change out the pump housings and impellers?
 
I’m NOT a gas engine guy, but if the thermostat is stuck open, I think you’d get low temp, not high... wouldn’t you? Maybe the thermostat is stuck closed, or as others have suggested, you damaged the impeller or clogged the system.
 
SeaGull
I am getting low temp.
The high temp alarm happened on grounding only. Now the needle pegs down.
 
Thank you BillK
One last question - one a standard basis, how often would someone change out the pump housings and impellers?
I change mine about every 3-4 years because I only have 3 months of a boating season. It's a PIA, but at $40 it's peace of mind.

I recently replaced the whole pump with a stainless steel one that has a replaceable back plate. The backplate can get scored, especially when running through 'sand' and reduce water flow or pressure through the pump.
 
IMG_4230.JPG
I’m NOT a gas engine guy, but if the thermostat is stuck open, I think you’d get low temp, not high... wouldn’t you? Maybe the thermostat is stuck closed, or as others have suggested, you damaged the impeller or clogged the system.
He is not overheating. He running cold, which is bad for plug life. The over heating happened before he cleaned things out. I might be inclined to try a new t-stat after running without it for a few minutes, just to see if the problem goes away. It doesn't take much to cause one to stick open. I had a similar problem years ago when coming into Leland Harbor when water level was way down. We bought a new t-stat at the gas station, installed it and the problem went away.
 
Flush the motor and install a new thermostat. I’d replace the impellers too just to be safe. You can take a look inside the pumps when you have the impellers out and determine if the pump(s) need replacing. Sand beats the hell out of impellers.
 
SeaGull
I am getting low temp.
The high temp alarm happened on grounding only. Now the needle pegs down.
Based on that temp I am inclined to think the sender may be damaged. It's real hard to run that cold even with the t stat removed. Did you use a temp gun on the t stat housing to get the actual temperature?
 
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