High engine temperature

[Mac5]

I flushed out all off the hoses and put a garden hose up to the transmission cooler with no engine hoses attached, turned on the garden hose and water flow was very good through the cooler. 

The only ones I have not checked are the really large hoses that lead to the exhaust in the back of the engine. Should those be flushed out? 

[footndale]

You could have very plugged exhaust manifolds.  I've seen it cause problems. Friends 02 Sanger had this problem and burnt the engine up. New engine and another bad manifold from the factory. 

I believe the Merc manifolds are more compact than Indmars.

[boardjnky4]

I'd be investigating the engine water pump (re-circulation pump). I've seen photos of them cracked in half on the inside, still pumping some water, but not enough to effectively cool the engine.

Edited June 26, 2017 by boardjnky4

[isellacuras]

I replied to your PM but I hadn't read this thread yet.  Here's a little story that I call the "Mystery Impeller".  I found a mystery impeller in my brother in laws 93 echelon several years ago.  I had changed two intact impellers the two years prior.  I was getting a high temp alarm so I did all the usual things, changed impeller (was intact), thermostat, ran without thermostat and temp sending unit.  When I hooked it up to the hose, it would run fine but on the water it would over heat.  After taking all the hoses off, I found almost a whole impellers worth of rubber deep in the metal hose just before the trans cooler (gotta dig your finger up in there).  The only thing I can think of is that the last impeller that had catastrophic failure (several years before) had lodged up in there and let enough water pass through to not overheat.  eventually it dislodged and blocked the passage.  I also believe that when I hooked it to a fake a lake, it created enough pressure to get passed the blockage.  It was a frustrating sequence of events.  Been running perfect ever since.

[ajacobsen]

Will a 1990 Sunsetter with 5.7L Mercruiser have the same potential blockage at the trans cooler? Also stalls after an hour, especially cocktail speed,  also won't accelerate after it gets hot. New thermostat just installed. On my third mechanic...nobody can figure it out. Thanks! 

[isellacuras]

I had no loss of performance

[ajacobsen]

Thanks Isella.....some similar symptoms of overheat, like a partial blockage. Next...theory....mechanical fuel pump failing when there is a partial overheat...and then check the fuel lines. Runs like a champ when it is cold. Carb rebuilt last year. 

[Steve B.]

11 minutes ago, ajacobsen said:

Will a 1990 Sunsetter with 5.7L Mercruiser have the same potential blockage at the trans cooler? Also stalls after an hour, especially cocktail speed,  also won't accelerate after it gets hot. New thermostat just installed. On my third mechanic...nobody can figure it out. Thanks! 

Search "vapor lock".

Steve B.

[BlackBluMalibu]

On 6/23/2017 at 10:22 PM, Mac5 said:

Changed thermostat and impeller... temperature shot up to 210 while I was leaving the dock. Did I install impeller wrong? 

Could be something clogging the oil cooler.  It has a screen in it and may be partially blocked.  Good luck, have safe and fun summer!

[Bozboat]

Could be the circulation pump.  Without a thermostat the raw water pump will probably stuff enough water in to the block to keep it cool, but at odd times it will still overheat. When mine failed, it was a random overheat event. 

New Pump looks like this

Edited June 27, 2017 by Bozboat
added link to new pump

[Steve B.]

On 6/25/2017 at 9:37 AM, Mac5 said:

Progress has been made...I had to cut the raw water line to work on the impeller because the hose was old, stiff and practically glued to the inlet coming into the boat.  I replaced this piece of hose with a new hose of similar strength rather than just a rubber hose. 

I got the impeller installed and also disconnected and flushed out every single hose along with the transmission cooler.  I also installed a new thermostat and hooked up a fake lake in the driveway. I turned on the boat and within a 1-2 minutes the temp was over 200 and a few hoses became too hot to touch so I turned off the engine immediately. 

I took the boat to a local parts place/mechanic and showed him how I installed the thermostat. He verified it was correct (it's very easy to do).  He told me to take the thermostat out and run the fake lake. I went home and did as he suggested. The boat stayed cool. Started at 120 got up to 160 then began to drop back down as it idled.  Let it run for about 5 minutes.  

I then took the boat out with the family without the thermostat and it ran perfect and stayed between 140 and 160 all day (mostly at 160).  At this point I may just run it without a thermostat for the summer and then take it to a mechanic or dive into it again in the fall.  Thanks everyone for the great advice! While it was a pain the last few days it was all worth it because I learned a ton about my first boat. 

 

Sumthin' funky going on with that thermostat. Honestly, if it doesn't get too cold where you are, you may think of just running without it.

Steve B.

[Bozboat]

Just now, Steve B. said:

Sumthin' funky going on with that thermostat. Honestly, if it doesn't get too cold where you are, you may think of just running without it.

Steve B.

Test the thermostat in a pot of water on the stove first. It should open and close quickly at the set temperature. The circulation pump failure is a less common problem.

[Steve B.]

I wonder if a thermostat housing could maybe hold the thermostat from opening all the way. Never heard of it. Just wondering. Not sure if his circulation pump has an inspection cover on the back, but it might be "fun", to yank that thing and take a look see. Good for you to shut it down as the temp tried to skyrocket.

Steve B.

 

[Michigan boarder]

Not much help here other than to add an odd perspective.  I bought my Echelon in '08 from a good friend of mine that had it since '02.  It never ran above 120 degrees since the day he took possession.  After I bought it, I bought a new thermostat and boiled it next to the old one.  Both appeared to open at the same time.  Installed it and the new thermostat never ran above 120 either, same spot on the guage.  We rebuilt the engine in 2014 and I put a new thermostat in.  Same temp.  Verified with an infrared gun.  A few weeks ago I pulled the thermostat and boiled it next to a new one, showing my son how this stuff works.  The old thermostat actually stayed closed longer than the new one.  WTH??  I installed the new one and now my temperature is right at 160 degrees.  Double WTH???  I'm going to name my boat Ruby Sue.

"She falls down a well, eyes go crossed.  She gets kicked by a mule.  They go back to normal.  I dunno."

 

 

[JasonK]

Yes the 1990 will have the same potential blockage at the trans cooler. You might want to try to bypass the trans cooler for a short run. It could have an internal blockage. I've also seen impeller pieces get past the trans cooler and into the block cooling passages, once, on a old nautique.

[Mac5]

I tested the new 160 degree thermostat in boiling water and it performed as designed.  I bought a new 140 degree thermostat anyways and plan on putting it in, in the fall.  In the meantime I plan to run with no stat because it is very hot in the summer here and the lake is pretty warm. 

Steve- I was thinking something similar as you with the thermostat not opening.  The new cap was so tight to fit in that I had to really press it down in there. Could it have created too much pressure on the top of the thermostat that doesn't allow it to open? 

Today I think I am going to tackle a few more tests as well. I am going to check exhaust manifolds for blockage and the metal hose before trans cooler. 

The re-circulation pump (as I think it's called... the one that houses the impeller) seems ok. 

Boz- Which is the circulation pump? I didn't see it in the manual when I did a word search for it...

Thanks everyone for the advice. 

[Steve B.]

Mac, the circulation pump is the "car" type one. Mounted right on the front of the engine, just above the crank. The "raw" water pump is the one that sucks water in directly from the lake from the bottom of your boat.

The "raw" water pump, is the one that is directly attached to your tranny cooler. 

Steve B.

[Mac5]

thanks steve

 

[Mac5]

How can you tell if the exhaust manifold is clogged? And where and what would it be clogged with? 

 

[boardjnky4]

the circulation pump is usually belt driven, so you need to take off the belt and the pulley. It should be near the top of the engine. You'll see the pulley/belt as well as the hoses from the T-Stat housing routing to it.

[Mac5]

So I took off the risers and exhaust manifolds and got my pressure washer and completely flushed them out.  There was a decent amount of dirt in them. Not sure if it was enough to be the source of the overheating. I took the boat out, the temp outside was only in the low 90's compared to 105 before and lake felt a little cooler. The boat ran about 148... 12 degrees cooler than before.  This could be attributed to the lower temperature outside or the cleaned out manifolds.  I'm tempted to put the thermostat back in but its running well and would like to just use it for the summer and quit messing with it. 

 

[Michigan boarder]

I would do the same, worry about a thorough check in the winter.

[Woodski]

@Mac5:  I suggest you install a thermostat, w/o one you run the risk that the water pressure in the engine is too low and you will increase the chances of air pockets at the far corners of the water path and localized overheating.  There needs to be some backpressure in the engine or behind the thermostat to ensure water fills all the cooling passages.  If you are still uneasy doing that, you could install a restrictor plate (basically take the guts our of the tstat) in place of an actual thermostat.  Are you running a marine style stat or an automotive one?

[Mac5]

Ok, I'll give it a shot and install one. I'm running a marine thermostat at 140.  I'm hesitant to install now because I stripped the the threads in the intake where the thermostat bolts goes into it, so I'm trying to minimize the amount of times I screw and unscrew that bolt.  I had to put a heli-coil in but it was my first time doing so and I made it at a slight angle.  Everything is working fine with it but like i'm trying to minimize screwing the bolt in and out.  Thanks for the heads up woodski

[Mac5]

Still running hot. I'm not sure what else I can do.  The gauge reads 195. With an infrared thermometer the manifolds are about 210 degrees. The risers aren't hot.  A few hoses are 180 others are about 70 or 80.

Here is what I have done: 

--Removed and Flushed out all hoses,  

--Removed and Flushed out risers

---Removed and Flushed out manifolds.

--Cleaned out the screen on the cooler (nothing much was there)

--Changed out the impeller. The previous impeller was in perfect condition. 

--Installed a new sender

--Installed a new thermostat

--Installed a new temperature gauge

--changed my oil

 

The only other thing is that the previous owner installed a new carburetor.  He told me the one that he was supposed to get wsn't in stock so he purchased a nicer one.  Is there a chance the carburetor is too strong or not the right one? 

Keep in mind, when the thermostat is out, it runs at about 140-160 degrees. 

Thanks, Mac