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Overheat and Low Top end speed

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Hey everyone,

I am a year old Wakesetter owner - dug into the forum last fall for winterizing advice and was impressed with the quality of information all around!!

This spring rolls around and I’ve got some issues with my 2008 Wakesetter XTI, Indmar Monsoon 5.7L 340. Hoping to get some ideas!

The issue first became evident when I smelled a burning rubber smell after cruising WOT for about 5 minutes. Upon investigation I found a hole in the rubber exhaust tubing - which appeared to be dry rot or aging of some sort. I replaced the hose, and next time out all seems to be going fine until I have issues making full power and get the burning rubber smell again. I had burned another hole in the new tubing, and now was only able to get 3500rpm and about 33-34MPH. The hole is in the underside of the port side softwall exhaust tubing - a couple inches aft of where it connects to the exhaust manifold, so I have to assume its hot exhaust gas hitting the hose directly with little cooling. It is worth noting that there was water spurting out of the hole both times it happened, but not a significant amount.  

Photos of Hose Here - Google photos album link

After about 10 hours searching the forums I decided to do a few simple things first...

1) replaced impeller and checked transmission cooler and all lines for debris- which I did find a fair amount of seaweed and 1 rubber fin from the old impeller. 
2) replace the fuel filter- the screw off in tank filter (I think that’s the only one I have)
3) replace the exhaust hose again

After these repairs, I fired up and checked a few of the hoses to make sure I was getting water flowing through the system - and as far as I could tell, it was running fine. However, as I was idling the engine got up to about 150 degrees, but immediately dropped back to 120 once I put it in gear and increased RPM slightly. Hoping the issue is resolved at this point. 

All is normal as I slowly continue to add power, until I get to WOT at 4900rpm...and I’m only going 33MPH with the engine is running at 160 degrees. After slowing to idle I feel the exhaust tubing and it feels extremely hot again - like it’s about to melt a third time. I back off the power and limp back home dejected and frustrated.

I'm going to do a more in depth check of the cooling system tomorrow, to verify I’m getting water in all areas but that still doesn’t address the top end speed. 

Oil is fresh and proper level, transmission fluid has not been changed but is leveled properly.

Any thoughts or directions I can investigate?? Thanks in advance!






Edited by Jwert
Added Pictures and Clarification
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Defective temp reading and a stuck thermostat?  I am guessing here as it sounds like you did the right things so far.  Maye there is something still plugging the water lines?

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7 hours ago, BlindSquirrel said:

Can you take a pic of the hose that melted and continues to melt?

I Just edited the original post and added a link to the pictures

8 hours ago, Eagleboy99 said:

Defective temp reading and a stuck thermostat?  I am guessing here as it sounds like you did the right things so far.  Maye there is something still plugging the water lines?

I was really hoping this was the case - but the engine is definitely getting hot. I dont think I've "Overheated" and damaged anything internally, other than the rubber hose....at least I'm hoping thats the case....

I'll report back after I check for good water flow through the entire system. 


Here is a link to the photos

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I ran through all the lines this morning and they all seem clear and to be moving water. I pulled a few of them off and momentarily bumped the engine - and it would fill a gallon bucket in no time. I did not pull off the circulation pump and check it, what part do you recommend checking? The brass gear that inserts into the center of the impeller??


A few observations:

- On startup everything seemed normal, except it warmed up to 16 within 3 minutes again while idling. Once I started moving it almost instantly cooled to 130 - almost faster than it looked possible. Maybe this does mean the temp probe isn’t working correctly?

- on WOT test again today, same results of 4900RPM, 33MPH but the GPS on my phone showed I was doing 40MPH (and it’s dead on accurate in a car) still should be getting a little better than that....

- after running wide open (15 seconds max) again the rubber softwall exhaust smelled like burning rubber, but only slightly and it did not burst. 

- again everything seemed relatively normal below 3000RPM, just seemed to get that hose hot when run anything above that. I specifically checked the water hose going to the back of the exhaust manifold and with the engine running it’s pumping lots of water out (at idle at least)


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59 minutes ago, Jwert said:

4900RPM, 33MPH but the GPS on my phone showed I was doing 40MPH

If you can't trust your speedo, who can you trust?  :)  That is one down.

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