Go Back   TeamTalk > Maintenance Tips, How-tos and Refurbishing Topics > Engine / Drive Train

Thread Tools Display Modes
Old 04-28-2015, 04:39 PM
FoggyNogginz's Avatar
FoggyNogginz FoggyNogginz is offline
MC Devotee
Join Date: Aug 2006
Boat: 2017 X10
Location: Center Hill Lake, Old Hickory, and Norris Lakes in TN
Posts: 1,862
I just thought I would dump this out there in case it helps:

On mine, we identified several culprits to investigate for cooling issues via the help of MC, MikeG, and many others on this forum. However, it also comes down to the fact that the raw water cooling system is really not efficient enough to properly prime under idle. Some may argue this point, but bear with me a moment. This is an issue for people like myself who take the boat out of the water everyday (or if you are running it on a hose in your driveway), because this model also has a dripless shaft seal so the water runs out of the shaft seal instead of remaining in the manifolds like it did on the indmar systems. So while you can run these models on a hose, I would not go much above idle when doing so, even if using the bucket method.

This being said, I have a few recommendations:
1. Check all hoses in the cooling system for debris, blockage, rubber pieces from the impeller.
2 Remove the flush pro if you have one to eliminate possible sources of air in the system.
3. Remove the seacock strainer from the system if you have one, and/or ask MC for the upgraded model of the strainer. I removed mine entirely because my lake is quite clean and I have never ran a boat with a strainer before. However, if you want to replace the strainer once your troubleshooting is complete....feel free.
4. This boat has a circulator pump and a RW pump. Occasionally, the circulator pumps will fail, and you can tell this from a visual inspection if you will take the pump apart on a bench to inspect it. I had my dealer do this at their request because reportedly some were breaking internally.
5. Because of the dripless shaft seal that I mentioned above, I would never run this boat on a hose out of the water for an extended period of time. Too much water is lost from the dripless shaft seal, and the system does not remain well primed.
6. Yes, the thermostat has a flow hole that must be aligned with the flow of the water. Apparently, many of these were installed backwards or not aligned at all from the factory. I cannot remember the exact setting, but I know that I made a post on here somewhere about it. If you cannot find this, please let me know. Mine was NOT properly installed, and the dealer caught this after three visits to their shop.
7. Next I agree with the above statement that the computer alarm may not be inline with the thermostat and the "normal operating range" for the engine. I experienced this as well and my dealer changed the alarm levels.
8. Finally, when you put the Ilmor back in the water, the sad truth on these systems is that you often have to prime the pump at the dock to completely fill the manifolds with water and drive the air out of the system. This is something that I initially heard form MC, but I have also proven this to be true in the past season. In order to do this, take the boat out of gear and rev the engine to 1500-2000 rpm for 30 seconds to completely prime the system. As long as I do this whenever I put the boat in the water now, it will not overheat. However, if I go several minutes at idle without getting under power, the system will never prime and it can/will get too hot.

Sorry for the long winded response, but I really hope that this helps. I love my boat, but it certainly had a few gremlins when I got it. I also understand that there is a new part number for the impeller all open cooled Ilmor engines except the Ilmor 7.L, and this is Part #PV06764, and this replaced MV8V-1178 per Ilmor's website.


Be sure to ask your dealer which impeller they have in stock because I had to call three shops last week to get the new one, which according to many on this site is made of a new rubber composition that is much more durable.

Best of luck, and keep us posted on your progress. I'd love to see that new Prostar too!
2017 X10 / 2012 X14v / 2002 X9 / 1998 PS205
Center Hill, Norris, & Old Hickory lakes in TN

Last edited by FoggyNogginz; 04-28-2015 at 04:50 PM.
Reply With Quote
Old 04-29-2015, 09:42 PM
Bruce-ActionWater's Avatar
Bruce-ActionWater Bruce-ActionWater is offline
TT Enthusiast
Join Date: Feb 2014
Boat: 1994 ProStar 190 LT-1 Slot
Location: Midwest
Posts: 301
In 2014 Ilmor had an issue where the thermostats were not being indexed right to allow the air bubble to leave the thermostat housing causing an overheat. Also there is a service bulletin out now to change out your thermostat to a different one and move the temp sender. Contact your local dealer.
Bruce Jesionowski - Parts & Warranty
Store: 810.629.1342
Action Water Sports-Fenton
8051 Old US 23
Fenton, MI 48430


1984 MasterCraft Stars&Stripes. Fully restored-SOLD
1994 MasterCraft PS190 LT-1 Slot
Reply With Quote
Old 08-07-2016, 12:47 PM
atthelake's Avatar
atthelake atthelake is offline
MC Fanatic
Join Date: Feb 2011
Boat: 2014, X30, 6.0 Gen2
Location: Saskatchewan, Canada
Posts: 742
Has this been an issue with the 2014 6.0 liters as well? Mine did exactly this yesterday for no "reasons" at all. All parts etc check out. You could see the temperature guage start to flutter and then just climb like crazy ( in low idle) . Rev up to 1500 and temp would drop like a rock.
Reply With Quote
Old 08-07-2016, 03:29 PM
Cyoder1 Cyoder1 is offline
TT Enthusiast
Join Date: Apr 2015
Boat: 2012 X25
Location: Northeast
Posts: 170
I sent an email directly to Ilmor when I replaced my thermostat. They told me that the bypass hole should be in the 12 o clock position, i.e. Straight up.

Reply With Quote
Old 07-28-2017, 08:52 PM
TNX5TY TNX5TY is offline
TT Enthusiast
Join Date: Jul 2014
Boat: 2001 X-5 Red/White
Location: NW Tennessee
Posts: 228
Reviving an old thread.

Buddy has a 6.0 Ilmor that had been noticing fluctuation of temperature to 200 and could put the boat in gear and the temp would drop to normal temps.

Surfed the other night and the temp pegged to 200. Shut it off , and got a tow to the dock.

Changed thermostat and ran fine on fake a lake .

Put it in the water today and idled and actually drove around a bit and had no issues.

Filled ballast up and surfed and temperature pegged to 200 again.

What's the issue here ? Impeller new last year . Haven't checked it yet but it's the next step.

In regards to the thermostat being set with hole at 12 o clock , we have some confusion there .
Does that mean that 12 o clock position is toward the motor or away from the motor .

Sent from my iPhone using Tapatalk
2001 X5
If I am not in my office, i'm on the lake or in one of my deer stands.
Reply With Quote
Old 08-01-2017, 01:53 PM
lentiman's Avatar
lentiman lentiman is offline
TT Enthusiast
Join Date: Sep 2011
Boat: 2012 MasterCraft X2
Location: NorCal
Posts: 278
Check the impeller. If the shaft is keyed make sure that the key didn't fall out when you changed it last year. Make sure there is suction from the thru hull pick up. Make sure the sea strainer is clear and that there are no air leaks.

I changed my impeller this year and finally determined that the key had fallen out.
Reply With Quote
Old 01-29-2018, 11:44 AM
NewName NewName is offline
TT Newbie
Join Date: Mar 2017
Boat: X 25 2011
Location: Germany
Posts: 21
Can anybody confirm the right position of the Thermostate ?
When I stand behind the engine looking ahead, should the hole be at 12 or 6 o clock position?
I just drilled mine abit bigger before winterizing but found my remark today to double check the position.

Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

All times are GMT -4. The time now is 12:13 PM.