Jump to content

Welcome to TheMalibuCrew!

As a guest, you are welcome to poke around and view the majority of the content that we have to offer, but in order to post, search, contact members, and get full use out of the website you will need to Register for an Account. It's free and it's easy, so don't hesitate to join the TheMalibuCrew Family today!

350 Monsoon "conditional" Overheating


Recommended Posts

50 minutes ago, funlife said:

July 25th 2018 - update. Problem never completely went away, yet lived with the occasional couple of times a year issue on this conditional overheating.  (below from my initial thread):

Overheat issue- Usually after a ski run, and then overheats at idle speed. Temp goes from a steady 160' (t-stat setting) while running ski sets, to 190' at idle, and boat alarms. Shut boat off, or take out of gear and run engine in neutral to about 2000 RPM, Temp comes back down- good to go.

It seems to have gotten worse this year (air and water temperature is hotter than past summers). So, I've ordered a new circ pump, and will change that this weekend. Worse case if that is not it, is that I now have a spare circ water pump for the boat!

One thing that I am questioning though- This boat has a water cooled propshaft bearing, with the water being tapped off the transmission cooler unit. This area drains out when the boat shuts off. clearly, this will create an 'air pocket' above this fitting on the trans oil cooler, probably up to the thermostat / intake area, including around the water temp sensor unit. (I removed the clear hose from the trans cooler to verify, and also started the boat with it disconnected to assure water flow back to the bearing).  Would this 'air pocket' that is created above the trans cooler be enough of an issue to overheat the water temp switch upon start up and low flow at idle?  Again, once the water flows, the temp drops, but if the boat goes into alarm, it will stay in alarm until I shut if off and restart.

Anyone have any experience with overheating attributable to the water line to the shaft bearing (tapped off the trans cooler unit)?

I still plan on changing the circ water pump this weekend. We'll see if it makes a difference. Curious on the water line to the shaft bearing, and the impact this plays on the overheating condition....

 

Pretty sure all of the boats take the shaft cooling water off the trans cooler.  Shouldn't cause any issue - half the cooling system self drains through the inlet when the boat is off anyways.

Edited by oldjeep
Link to comment
  • 2 weeks later...

Son of a Bit...….

Still alarming for temp overheat after a ski run. This morning on restarting after a ski run, the engine was at 209'.

Changed:

- Impeller

- Circ Pump

-Thermostat

- Cleaned Trans cooler screen

- Checked all hoses, fittings, and outlets from bottom of boat to engine for any debris

I'm beginning to think that the water line off the trans cooler to the shaft bearing has something to do with it. When I pull the clear hose off, it is dry, meaning the cooler is dry, and all above it must run out, including to the intake. Then, on start up, the temp switch is "hot" due to the motor being warm, and no coolant in this area.  When I start the boat with this hose off, water is flowing at good pressure down the fitting on the trans cooler that goes to the bearing. Hence, some loss of water, and possible starvation of water up to the intake and the temp switch.

Appreciate if others with water cooled shaft bearings can look at the photos, and let me know if they see anything different than your set up. Also, it seems my hose is 1/4" diameter (shown in photo, coming off trans cooler) - 

 

(seems I can't attach a picture - can anyone help me with sending / attaching - thanks)

 

 

 

 

 

Edited by funlife
Link to comment

My water cooled shaft seal behaves exactly the same. Clear hose runs dry as soon as the engine is killed. Never had an overheating issue though.

Link to comment

Chaabo - do you just ski one set, or do you have a rotation of skiers?  I can go out and ski a set, and bring home - no issues. But after a set, even to shut the engine down to get in boat and change skiers.... it starts up at 200+ degrees.

 

Link to comment

Have you ruled out this being an instrumentation problem?  On my boat, I have installed a second  water temp and oil pressure gauge (both mechanical) to monitor problems like this.

Link to comment

Yes. Two ways, also changed temp sensor over the winter lay up, as well as using an infared thermometer shooting at base of temp switch. Although not perfect, infared reads about 195 (boat gage at 210 - infared from harbor freight... 'nuff said), and then when pulling pin to increase rpms, can watch temp drop on infared as well.  

Slowly convincing myself that something is not getting the water up into the intake fast enough, or with enough volume after turning the boat off and then back on after a ski run. Once underway (if not in alarm, even if elevated temps), all good at 160'.

With the trans cooler draining, it seems to me that this entire cavity (t stat housing, intake cavity) would also drain out the water line to the shaft bearing.

Is it possible that there is something missing that should keep the water in the t-stat housing / intake when the water drains out the water line to the shaft bearing?

 

Link to comment
3 hours ago, funlife said:

Chaabo - do you just ski one set, or do you have a rotation of skiers?  I can go out and ski a set, and bring home - no issues. But after a set, even to shut the engine down to get in boat and change skiers.... it starts up at 200+ degrees.

 

We usually ski 2 sets (my wife and I) and shut down the engine in between sets to change ropes, ZO settings, gear, ...

Takes a good 5 - 10 Minutes.

Normal engine operating temps are about 165°. Spot on. After restarting the engine, the temp gauge is reading about 185° but it takes just about 10 seconds to get back to normal. These readings are always the same, no matter how hot the Floridian weather or what’s the water temp.

 

Link to comment

Chaabo - when your gage is at 185 and takes 10 seconds to get to 165, it that at idle (in or out of gear), or is that at a higher RPM?

I'm about ready to dismantle the entire water feed system to figure this out.... I've put all new marine certified parts in already.  Just can't get past the leakdown of the water down the water line to the shaft bearing though.  

Something still aint right....

 

Link to comment
15 minutes ago, funlife said:

Chaabo - when your gage is at 185 and takes 10 seconds to get to 165, it that at idle (in or out of gear), or is that at a higher RPM?

I'm about ready to dismantle the entire water feed system to figure this out.... I've put all new marine certified parts in already.  Just can't get past the leakdown of the water down the water line to the shaft bearing though.  

Something still aint right....

 

Please list what you replaced.

Did you replace the circulation pump?

Edited by Bozboat
Link to comment
1 hour ago, funlife said:

Chaabo - when your gage is at 185 and takes 10 seconds to get to 165, it that at idle (in or out of gear), or is that at a higher RPM?

I'm about ready to dismantle the entire water feed system to figure this out.... I've put all new marine certified parts in already.  Just can't get past the leakdown of the water down the water line to the shaft bearing though.  

Something still aint right....

 

Just idle. No need to rev it up.

Did you by any chance use a Globe blue impeller? I tried one of these a couple years ago and my engine wouldn’t pull enough water at idle to fully prime the cooling system. Had to rev it up at every start to avoid overheating. (Changed back to a black impeller pretty quick).

Edited by Chaabo
Link to comment

Parts Replaced:

- Water Temp Switch (GM Delco)

- Impeller (Johnson SPx MC97), plate gasket

- Circulation (Engine water) Pump (Sierra Marine), gaskets

- Thermostat 160' , T-stat gasket (Marine - from Ski DIM)

Cleaned:

- Transmission cooler screen

- Tstat housing and intake (as far as I could reach)

- Intake screen on bottom of boat

- Intake line from screen to impeller pump

Verified:

- no leaks throughout system (hoses, clamps, gasketed surfaces, etc) - hull is dry. All lines and connections to heater above foot well dry. 

- Valve open after 90' bend (hard pipe) from screen to hose

- Water flowing after impeller pump, line out to shaft seal, hose to t-stat housing (by briefly starting boat on lift with hoses removed and verifying water flowing - yes, a whole lot of water!)

Again - engine  runs fine at speed (160' on gage), and can do so indefinitely. Only overheats after a run at speed (typically 34mph, but will also do if running at just about any speed over about 25mph), then shut engine down (about 2-5 minutes), then restart. If only at idle, or in gear at idle, engine temp will rise from about 180-190, and alarm at about 206-210. Shut boat off, restart again and rev engine (with pin pulled), and temp will come back to 160. Push pin in, and good to go.

All things point (to me anyway) that the intake and t-stat cavity is draining due to the water line to the shaft seal. I'd like to post a picture of the line coming off the trans cooler to have someone verify that all is good with this line from the trans cooler. Appreciate if anyone can let me know how to post or embed photo to post - maybe this will help-

Thanks all for hanging with me until we can get this resolved!

Edited by funlife
Link to comment

Just pulled off hose from trans cooler to t-stat housing. Wanted to see how long it took for water to flow up to housing. Both cold start, and when engine at 160'.  Both conditions, was under a second (yes, with a stopwatch- about .5 sec cold, about .7 sec warm - yet I think the same, due to how fast I hit the start / stop). So, water getting to housing pretty quick....

So, the question remains.... why is boat overheating after a ski run? Air pocket that isn't moving by temp switch????

Link to comment

Sounds to me like the raw water pump isn’t drawing sufficient water. At speed this wouldn’t present itself because of the speed of the boat. I would look at the raw water pump impeller again and make sure it’s drawing sufficient water at idle. 

 

Link to comment
34 minutes ago, wakeparadise said:

Sounds to me like the raw water pump isn’t drawing sufficient water. At speed this wouldn’t present itself because of the speed of the boat. I would look at the raw water pump impeller again and make sure it’s drawing sufficient water at idle. 

 

Agree 100%. The impeller could be shot, however at higher RPM’s it’t able to spin fast enough to draw enough water to cool. 

Edited by srintx
Link to comment

Just take the hose off downstream of the pump, run the engine for a few seconds and see how much water comes out. It should be ALOT of water even at idle. 

Link to comment

Replace impeller again. (Never hurts to have a spare anyway) sometimes they look perfectly fine but spin on the brass bushing they are glued on under load.

Link to comment

Checked the incoming water above the transmission cooler. A lot of water, and not a lot of delay (about 1/2 a second). I ran this with the hose off the trans cooler at start up, and about 700 RPM (in neutral and idle rpms).   So as long as I'm getting a lot of water at start up/ idle (enough that I had to lift boat on lift, and pull drain plug after performing this test - probably about 30-40 gallons in about 30 seconds...), I tend to rule out anything between the water intake on the hull, all the way up to the t-stat housing. This includes the impeller for two reasons - 1. A lot of water coming through. 2. I've changed the impeller twice, and issue does not change for the better or worse. This includes my thought of the water line to the shaft bearing as well. As I'm getting a lot of water out of hose to t-stat housing, so logic would say that the water line off transmission cooler to the shaft bearing is no longer a consideration. 

Took it out again today a few times, and same thing - after a run at speed, shut it down to pick up person, upon start up - engine is hot (195').  Pulled engagement pin on throttle, and watched temp come down.  Then no issues, both at idle and at speed. Temp holds within a couple degrees of 160.

My theory is that there is an 'air pocket' that forms in the upper intake area, and right near the temp switch. Once I shut is down , the area drains (through the prop shaft water cooler line). Upon start up, the 'air pocket' is trapped there (by the temp switch) until enough water pressure moves it out. Without moving it out (by revving the motor), the temp switch is not in water, and hence can read the 'air pocket' and not the water, which due to the temp of the intake in that area without touching water, could be hotter than the water in the intake cavity....

Obscure ? maybe - but I'm running out of thoughts and options....

Appreciate your thoughts, and other possible tests to run to try to resolve this nagging issue-

 

 

 

 

Link to comment

Bozboat - Yes, I used an infrared thermometer (from harborfreight). While not exact, was close enough to show it was hot at the temp switch. (195 on infrared temp sensor, 210 on gage). When engine cools down by revving engine, both come down to about 160'

 

Link to comment

Does your raw water pump still have the brass "hump" inside the housing?  I guess it's more like a ramp, but it is what forces the impeller blades to bend over on the output side of the rotation, causing the water to get squeezed out of the pump.  I'm thinking that maybe yours is missing somehow.

Link to comment
6 hours ago, funlife said:

Bozboat - Yes, I used an infrared thermometer (from harborfreight). While not exact, was close enough to show it was hot at the temp switch. (195 on infrared temp sensor, 210 on gage). When engine cools down by revving engine, both come down to about 160'

 

I am stumped.

Link to comment

I just consulted with my mechanic, he says it’s most likely the raw water pump. It may look like it’s moving a lot of water at idle but it could be just an illusion. The other thing he says is to check where the water exits the block; if that’s partially blocked it would affect the needed-flow of water. Check the elbow of the 90 degree valve, make sure there’s no blockage along that route. 

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...