2003 Monsoon 335 Overheating

[JasonK]

Could the inlet and outlet hoses of the johnson pump be mixed up? They both come to the bottom of the pump don't they?

The boat doesn't overheat when run with no thermostat. Is there anything in the thermostat housing that can break or be installed upside down?

[powbmps]

6 minutes ago, JasonK said:

Could the inlet and outlet hoses of the johnson pump be mixed up? They both come to the bottom of the pump don't they?

The boat doesn't overheat when run with no thermostat. Is there anything in the thermostat housing that can break or be installed upside down?

No to the first part.  New Indmar thermostat will be here Thursday.  Hopefully testing it out on Friday.

[Eagleboy99]

1 hour ago, powbmps said:

No to the first part.  New Indmar thermostat will be here Thursday.  Hopefully testing it out on Friday.

For fun, test your old t-stat (boiling water trick)

[Slayer]

I had some similar issues on my '06 at the beginning of last season.  It turned out to be, after ruling out most other things, that the raw water intake hose was sucking air.  I replaced it, and the problem went away.  This past season I replaced the thermostat. 

[powbmps]

On 10/20/2020 at 3:51 PM, Eagleboy99 said:

For fun, test your old t-stat (boiling water trick)

Boiled the new Indmar one with the old one.  They both seem to open at almost the same time.  Oh well, what's another $50.

Just trying to understand why it doesn't overheat with a constant 3/8" opening, but does with a properly functioning thermostat (which when open, is definitely allowing more water through than a 3/8" hole does).  Making my brain hurt. 

[Eagleboy99]

Just now, powbmps said:

Boiled the new Indmar one with the old one.  They both seem to open at almost the same time.  Oh well, what's another $50.

Just trying to understand why it doesn't overheat with a constant 3/8" opening, but does with a properly functioning thermostat (which when open, is definitely allowing more water through than a 3/8" hole does).  Making my brain hurt. 

Well that is strange.  I don't know what to suggest.  Maybe some blockage elsewhere?

[Eagleboy99]

Another thought.  Could you try running it WITHOUT a thermostat?

[powbmps]

5 minutes ago, Eagleboy99 said:

Another thought.  Could you try running it WITHOUT a thermostat?

It runs without a thermostat, but does not warm up above 120 degrees or so.  I tried a gutted thermostat, and it didn't get much hotter.  The 3/8" hole keeps it right at 160 when idling, but runs a bit to cool when under way.  

I have a few freeze plugs left, so I may knock them out and poke around some more.  See if I can find any blockages.

[Eagleboy99]

I think you are on the right track.  IMO the thermostat is not the problem.  BTW, The last stat I got cost me like 20 bucks.  Where did you get yours?

[JasonK]

That's odd. The boat won't heat up to 160, at idle this time of year in michigan. I was out last night and I was going slow for more than 15 minutes and it didn't reach 160. But when I went about 25mph it came up to 160 within 60 seconds. You're in New Hampshire, what's the lake water temp?

You ran the boat without a thermostat and the temp came up to 160 when you were just idling? And when you accelerated the temp dropped? Sounds like good flow. Prob a pressure issue.

Maybe you should bypass the transmission cooler for a short ride.

[Fffrank]

Have you back flushed your transmission cooler and lines?  I had some cooling issues this summer and found 15+ years of burnt up impeller fins in there.  Now I have cooling but no heat at idle.  

[malibu2004]

Just now, Fffrank said:

Have you back flushed your transmission cooler and lines?  I had some cooling issues this summer and found 15+ years of burnt up impeller fins in there.  Now I have cooling but no heat at idle.  

Most boats don't have heat at idle. You can get an y adapter that will help. 

[Woodski]

@powbmps - Do you have a laser pyrometer?  If yes, run the speed to idle test to create the temp overshoot and see if the pyrometer matches (or not).  I went through a similar scenario and the gauge and pyrometer readings did not match.  My theory is when you pull the throttle back to idle, the loss of pressure allows the temp / alarm senders to be exposed to air thus reading higher until the system catches back up to itself.  I theorize this is due to lack of enough back pressure on the exit side to keep water in constant contact with the sensors, which are mounted on the upper wall of the water exit channel.  Changing thermostat helped, and I went to a higher temp version for the fall cool temps.  Caveat, my setup is my own creation so your results may differ:-)  Also, changing raw water impellers of pump housing also makes a difference, that improves the low speed sealing if the ones in use are weak, damaged or worn. 

[Texan32]

any chance that you are running lean at idle?  Perhaps your injectors are clogging and down low your AFR is spiking and causing the overheating

[powbmps]

Thanks for all the suggestions guys!

On 10/21/2020 at 8:02 PM, Eagleboy99 said:

I think you are on the right track.  IMO the thermostat is not the problem.  BTW, The last stat I got cost me like 20 bucks.  Where did you get yours?

I'm thinking you are right.  I bought an Indmar thermostat from Bakes.

On 10/22/2020 at 8:48 AM, JasonK said:

That's odd. The boat won't heat up to 160, at idle this time of year in michigan. I was out last night and I was going slow for more than 15 minutes and it didn't reach 160. But when I went about 25mph it came up to 160 within 60 seconds. You're in New Hampshire, what's the lake water temp?

You ran the boat without a thermostat and the temp came up to 160 when you were just idling? And when you accelerated the temp dropped? Sounds like good flow. Prob a pressure issue.

Maybe you should bypass the transmission cooler for a short ride.

Water was 55 yesterday.  Without a thermostat, the engine wasn't getting above 120 or so.

On 10/22/2020 at 11:19 AM, Fffrank said:

Have you back flushed your transmission cooler and lines?  I had some cooling issues this summer and found 15+ years of burnt up impeller fins in there.  Now I have cooling but no heat at idle.  

Yes.  Pulled all the hoses.  Looks clear through the cooler itself.

On 10/22/2020 at 4:17 PM, Woodski said:

@powbmps - Do you have a laser pyrometer?  If yes, run the speed to idle test to create the temp overshoot and see if the pyrometer matches (or not).  I went through a similar scenario and the gauge and pyrometer readings did not match.  My theory is when you pull the throttle back to idle, the loss of pressure allows the temp / alarm senders to be exposed to air thus reading higher until the system catches back up to itself.  I theorize this is due to lack of enough back pressure on the exit side to keep water in constant contact with the sensors, which are mounted on the upper wall of the water exit channel.  Changing thermostat helped, and I went to a higher temp version for the fall cool temps.  Caveat, my setup is my own creation so your results may differ:-)  Also, changing raw water impellers of pump housing also makes a difference, that improves the low speed sealing if the ones in use are weak, damaged or worn. 

Yes.  One side was originally getting hotter than the other (~matching the gauge and alarm). Flushed out the block, thinking I had figured out my problem.  Now both sides are too hot .

22 hours ago, Texan32 said:

any chance that you are running lean at idle?  Perhaps your injectors are clogging and down low your AFR is spiking and causing the overheating

I like this theory.  Planning on pulling the injectors when I put the boat away, and dealing with them over the winter.

[Texan32]

because we run EFI systems, running an open t-stat will usually not end well.  The ECU needs to see a minimum temp in order to run closed loop and having no t-stat doesnt allow that (or takes significantly longer to get there).  Ironically, in an automotive application, running an open t-stat typically leads to running hot.  The water flows too fast and cannot transfer heat across the radiator.  This is why those who do run no t-stat, usually run a restriction ring (aka big a$$ washer).  

If you are worried about air pockets in the cooling system, I like to drill a small (sub-1/8") hole in the t-stat.  This allows just enough water/air to bypass the t-stat and allow the system to burp easier. 

[justgary]

2003 monsoon runs open loop all the time.  It doesn't have O2 sensors to provide feedback. 

[Texan32]

3 minutes ago, justgary said:

2003 monsoon runs open loop all the time.  It doesn't have O2 sensors to provide feedback. 

that makes ZERO sense to me.  seems like alot of money in parts just to get a minimal gain over a carb. 

Any chance yo can explain the thought process behind this?  Im genuinely intrigued. 

[Fffrank]

1 hour ago, Texan32 said:

that makes ZERO sense to me.  seems like alot of money in parts just to get a minimal gain over a carb. 

Any chance yo can explain the thought process behind this?  Im genuinely intrigued. 

My understanding is that it wasn't practical to add o2 sensors in the wet exhaust manifolds because they'd be constantly fried.

[justgary]

5 hours ago, Texan32 said:

that makes ZERO sense to me.  seems like alot of money in parts just to get a minimal gain over a carb. 

Any chance yo can explain the thought process behind this?  Im genuinely intrigued. 

I didn't dresign it, so I can't comment on the thought process.  I'll take my open loop monsoon over a carb any day.  Superior cold starts, no tinkering, high reliability, and the ability to diagnose problems all come to mind.  The ECM measures altitude and engine load in an attempt to optimize performance in current conditions. 

Keep in mind that while they might leave a little power by running the engine a bit rich, your car engine is not programmed for maximum power, but for minimum emissions. 

[powbmps]

Won't know until spring what difference it makes, but the fuel injectors were a mess. Injector report from R.C. Fuel Injection:

[Texan32]

16 hours ago, powbmps said:

Won't know until spring what difference it makes, but the fuel injectors were a mess. Injector report from R.C. Fuel Injection:

 

WOW!  Those are some pretty alarming numbers!  #8 was 100% blocked. I really like the fact that they gave you the before and after report.  I dont know if that common or something you asked for.  Its really nice to see the data.  It deff tells you they weren't playing nicely and could certainly be causing some of your headache.  Will it cure your issue?  Cant say.  But i would put money on it that it will run a hell of alot better.  

[justgary]

18 hours ago, powbmps said:

Won't know until spring what difference it makes, but the fuel injectors were a mess. Injector report from R.C. Fuel Injection:

Roughly what was the cost of that service?  How long did they take to do it?

From the report, I presume it helps you a lot to label the injectors as you remove them so they don't just arbitrarily number them for you.

[dtm8119]

It's nice to see the before and after data!

I'd be interested to see what the spark plugs look like for the corresponding injectors.  

[Texan32]

1 hour ago, justgary said:

Roughly what was the cost of that service?  How long did they take to do it?

From the report, I presume it helps you a lot to label the injectors as you remove them so they don't just arbitrarily number them for you.

Thats a great idea!  Hind sight is 20/20 (assuming he didn't already do that).  Also interested in the cost.  Based on the results he got, threre might be a number of people who might benefit from a service like this.  And if the price isn't over the top, it might encourage more people to do it. 

Edited December 9, 2020 by Texan32