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!

2000 Sportster LX (5.7 Indmar) - Engine Running Temperature


Recommended Posts

Hi All, 

I've had my Sportster LX which is new to me out a couple of times. 
Running great on a new Holley 650CFM carb. 

However, I just wanted to check the standard running temperature of this boat? 

At its lowest, it's running at 160 degrees. 

It's it just ticking over in neutral, that can shoot up to around 190. 
Once I'm running on the plane, It'll go back down to about 165/170 degrees. 

I've a feeling that's a little high? 

I've noticed a small drip from the back of the Johnson Water pump, so I need to replace the main seal and maybe the bearings in it. 

Is there anything else I should be looking into? 

Thermostat / Gauge etc. 

Also my oil pressure gauge seems to be intermittent.  Could just be a faulty gauge though? 

Any help would be greatly appreciated. 


Link to post

Should stay pretty rock steady at 160deg under any condition.  Your thermostat is maybe on its way out.  Replace it, it's easy to do.

Water pump just buy a new one, and replace.  Again a quick and easy job.

Oil pressure, likely the gauge check your grounds check for corrosion on wiring around the gauge.  If not that, check resistance through the wiring, then check the sender.

  • Like 2
Link to post

If I understand, your temperature will rise while the boat is at idle and cool down when at speed.  The temperature will rise when the engine is off, shut down after a run etc., but will quickly cool down when the water starts flowing again.

1) verify the engine temperature with an infared thermometer, If the temperature is ok, then start checking sensors and wiring for your gauges.

2) repair or replace the raw water pump, the drip indicates it needs help

3) new impeller? Install with some dish soap, not dry.

4) new gasket for the raw water pump.  Don't reuse the old gasket

5) are the clamps tight on each water hose connection?  No chance of an air leak?

6) Flush the transmission cooler to make sure no debris is clogging the path from the raw water pump to the block

7) If 1-5 check out, then look carefully at the circulation pump.  A broken impeller in a circulation pump will cause the engine to overheat at idle and at full power, in between idle and full power the raw water pump will push enough water thru to keep it cool.

Link to post

From my guide I put together from numerous posts here...the 1st bullet point after "NON MONSOON ENGINES ONLY" might be applicable to you.



***IMPORTANT: do not run in overheated condition!

  • Verify the raw intake valve is completely open; or if utilizing a flush or fresh water intake that the water input is routed from an open port/hose/valve as appropriate.
  • If on land, verify good water pressure to water intake. Note that when using any type of external system it could mask a cooling issue. Avoid using a fake-a-lake if at all possible; permanently installed flush valves are far better and safer. 
  • If on water, bump the throttle to “prime” impeller in case of air in system.  If you have a “run dry” impeller (such as the Globe 100J) they are known to be prone to priming issues at times; if so, a short 1500-2000 rpm engine rev should prime it.
  • Verify the impeller is good; inspect or replace with new if ANY overheating.  Although your impeller may appear pristine, there have been failures where the shaft rotates inside the rubber impeller, resulting in no rotation of the impeller.
  • Verify the transmission cooler screen (and raw water intake screen) is clean  Any damage to impeller will go downstream and could clog the trans cooler screen.
  • Verify the thermostat is good.  They are inexpensive, replace if in doubt.
  • If overheat condition is based solely on an instrument indication, then verify the temp sensor is good. They are inexpensive, replace if in doubt.  There are up to 3 temp sensors, depending on engine: 1 sensor for dash, 1 sensor for ECM, and another for light/buzzer (older models.) 
  • Any small openings or leaks can allow air to be sucked into system upstream from impeller resulting in no prime or loss of prime.  Verify all hose clamps are tight and hoses are not kinked. Trace from the raw water intake through the entire system.  Check for loose hose clamps along the way and any kinking, especially around the tiller arm area upstream of impeller. 
  • Verify circulation pump is working.  If overheating at speed vs idle, it may be that pump.  Remove the drive belt and open the top port on the circulation pump and then turn the circulation pump by hand, with water in system you should see movement.  If a broken pump is suspected, remove entire housing and shake: if you hear noises, it is a broken circulation pump.
  • If you have a heater verify the heater circulation pump is running. You will get heat even if it isn’t running so don’t make any assumptions based solely on if you have heat. If it isn’t running first check the fuse for it.


  • Verify the vent line to transom is clean. On the transom you’ll see a little metal port about the size of a button. After running the engine and shutting down it will continue to vent water like its peeing for a few minutes. If it isn’t venting water it’s plugged up. There’s a hose that will run to the top of the engine. Take that hose off and blow it out with compressed air.
  • Verify the shaft seal is NOT plumbed into the transmission cooler. On an L96 the transmission cooler is on the vacuum side of the cooling system so if the shaft seal is plumbed into the transmission cooler you’ll suck air. If it is plumbed into the transmission cooler you can get a brass plug to screw into the transmission cooler and a T from your dealer to plumb the shaft seal into the correct place.
  • Check your engine serial number. Indmar published Service Bulletin SB2012-3IN to address a cooling issue with the L96 motor. It affects 2012 and 2013 L96 (6.0) and LS3 (6.2) engines with tube and tube exhaust manifolds and 7-digit serial numbers before serial number 2249300.


Link to post

Join the conversation

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

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...