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

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.

Work done so far:

I've replaced Impeller (old impeller looked good, but still replaced), replaced T-stat (old one had some corrosion, but nothing bad, but still replaced), checked Transmission cooler grating (clear), checked water grate on hull (clear). I've discounted the sensor, as it does vary, and reads temp from a cold start up to 160' (and beyond at idle after running), so I think sensor is fine.

Still having issue. When baot is running at speed, temp is a solid 160' and moves only a couple degrees. Yet when I come to idle, the temp rises, fast.

Any ideas for next steps to check?

(Malibu Repsonse with a Monsoon 350)

Link to comment

Read through that thread. Bilge is dry, but will check hoses with a light and magnifying glass, looking for possible places the impellor is sucking air in. Wouldn't it be "worse" (more air getting pulled in) at speed though, rather than at idle?

Link to comment

I would think at speed even though air is being introduced, the suction of the impeller would be greater resulting in enough water to be introduced to keep the engine cool. When slowing down and RPM's come down, there is not near as much suction so more air than water could possibly be coming in resulting in the higher temps at idle. This is only what I am thinking, maybe someone else will come along and add something if I am far off base.

Link to comment

Also, what would be the "symptoms" of having the engine water pump having an issue? If the Impellor is good, and the T-stat is good, and the lines are clear, what would a faulty/ failing engine water pump do?

Link to comment

Replaced a Johnson with a Johnson. Dont have the P/N's handy, but was right out of the Indmar Manual.

If it is a Johnson I'd say that's not the issue. Reason I ask is I put a globe in my last malibu, it wouldn't prime. Replaced it with another globe, and then after 25 hours it started having issues very similar to yours.

Link to comment

I would think at speed even though air is being introduced, the suction of the impeller would be greater resulting in enough water to be introduced to keep the engine cool. When slowing down and RPM's come down, there is not near as much suction so more air than water could possibly be coming in resulting in the higher temps at idle. This is only what I am thinking, maybe someone else will come along and add something if I am far off base.

I think that was part of my problem, the flush pro was cracked and at low RPMs I was losing the impeller prime as 99 response puts it. At higher rpms, not a big deal. I put a new hose on today and will be on the water Sunday and see what happens.

Link to comment

If your boat has a strainer, check to see if the o ring is still there. If its not, you may have found your problem. I had a similar issue on our moomba outback last year and a simple o ring fixed the problem. The water circulation pump may also be the culprit.

Link to comment

Make sure you didn't get the shorter impeller by accident. They make a 2" and 1 7/8" some have accidentally installed the shorter one and although it pumps some water they cause the engine to overheat when running at speed.

Link to comment

Checked all hoses from the hull pickup through to the impeller housing. All tight, no signs of drips, no leaks from any area.
Will pull the cover off the impeller housing tonight, and see/verify impeller flush with housing flange.

Any thoughts of engine water pump? what symptoms will a failing engine water pump display?

Link to comment

Yes to both. Heater is used often for the AM ski runs. Shower barely used this time of year.

Yesterday, every time after a ski set, once I picked up the skier and idled, boat started to heat up. Shutting it down and restarting, or pulling the neutral pin and revving the engine to about 2k RPM for a few seconds brought the temp right back down.

Link to comment

Could very well be the engine circ pump. Only way to tell is to take it off and shake it. If it rattles it's definitely bad.

Peter

f1731f8b-1fad-46b9-ad28-df1fdd0bf8a4_zps

Edited by SmoothWaterMan
Link to comment

Smooth water man:

Thanks, and it seems that I'm eliminating many other possiblities- I just don't know if the 'symptoms' I have (overheat at idle, goes away under power or revving engine, runs right at 160' under power, etc.) ties into a failing/ failed engine water (circulating) pump.

Could a raw water pump (impeller) keep an engine cool at speed (~ 3400 RPM skiing, ~2000 RPM 'revving' the engine) with a failed engine water pump? Is that possible at higher RPM, yet not enough at idle (~ 600 RPM) and create an engine overheating condition?

If you (or any other Malubu Crew members) could shed some light on the 'symptoms' of a failing/ failed engine water pump, I'd appreciate it-

Thanks!

Link to comment

Yes to both. Heater is used often for the AM ski runs. Shower barely used this time of year.

Yesterday, every time after a ski set, once I picked up the skier and idled, boat started to heat up. Shutting it down and restarting, or pulling the neutral pin and revving the engine to about 2k RPM for a few seconds brought the temp right back down.

I seem to recall some people who have an overheat situation with both shower and heater that a new valve or aux pump was sinatlled but recall they were all 6.2s...I'd call Indmar and be sure to mention heater and shower

Link to comment

smoothwater:

thanks for the post - where did you get the pic/video from.

Looks like a marine part since its painted black.

What other sorts of symptoms did it have if it was off a boat.

Any idea as to age or hours?

cheers.

Link to comment

Hey Funlife,

I thought i'd post here - my problem ended up being like SmoothWater - broken circ pump. If you recall mine overheated at higher rpms however as opposed to low rpm. If you look in my original post I gave a quick way to test the circ pump without taking it off.

Cheers

Link to comment
  • 9 months later...

Hey Funlife,

I thought i'd post here - my problem ended up being like SmoothWater - broken circ pump. If you recall mine overheated at higher rpms however as opposed to low rpm. If you look in my original post I gave a quick way to test the circ pump without taking it off.

Cheers

How did you test the circ pump without removing it?

Link to comment

smoothwater:

thanks for the post - where did you get the pic/video from.

Looks like a marine part since its painted black.

What other sorts of symptoms did it have if it was off a boat.

Any idea as to age or hours?

cheers.

Sorry this is a year late, I didn't see the post last year. I took the photos and the video. We are a Malibu dealer.

Peter

Link to comment
  • 4 years later...

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....

 

Link to comment
41 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....

 

The symptoms you describe mirror my experiences before I discovered my circulation pump was broken. 

  • Like 2
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...