M-25XP running hot + white smoke

[Ron Hill]

Derek : If you want to check the thermostat - put it in a pan of water on the stove with a candy thermometer.  Watch it open and note the temperature.

You need to seriously wipe down the entire engine to find out where the oil is coming from!  The valve cover? The oil pan vent hose? The dipstick not seating?  Hose from dipstick bottom to oil pan?  Oil sending unit on port side of engine block?   etc.

Engine temp - you need to snake &or change out all the raw water hoses? remove the HX and have it boiled out? get a new 160F thermostat? maybe just remove the thermostat and see what happens to the engine temp?

I believe that you have properly "Burped" the water heater hoses properly - the engine is just running too hot.  You might want to change the internal coolant (50/50 Prestone), but use radiator cleaner first. 

A few thoughts

[glennd3]

On the oil leak I would check the dip stick for wear at the seal and the oil sender. Although the dipstick is on the other side from the alternator it will leak enough to make a good mess. There are ample threads on these on the site.

[KWKloeber]

[Clarification- the dipstick hole is on the side (not front side) NEAR the front of the engine.]

Derek

There is a hole into the engine block for a dipstick on the port side, front side of the engine -  see the XP parts manual and the kubota parts manual for the location. If the plug is bad you can plug it with a rubber "well nut" from the hardware store (giggle search it.) 

Are you sure it's smoke and not steam -- which can happen w/ insufficient seawater flow -- the exhaust doesn't get cooled enough and vapor is pushed out with the exhaust gasses.

Is the temp sender and gauge good?  You can check the sender resistance at various temps -- see the Teleflex troubleshooting guide o the Wiki site >Engine.

A bad sender wire (or connections) or a poor ground at the sender will cause a low reading not high reading.

If you still have air in the system it must be in (1) the coolant pump (airlock) or (2) in the circuit to/from the heat exchanger.  The loop to the water heater is separate and doesn't cool the engine (once the domestic water gets heated.)
There's two separate circuits (loops) -- the water heater loop could be disconnected or pinched totally closed and it won't overheat the engine.  But air in that loop could move to the pump and then overheat.   
See here for the two separate and distinct circulation loops:
https://c34.org/wiki/index.php?title=Flow_directions_in_engine_cooling_hoses_(both_early_and_B-series_engines)

[Derek]

Derek, by scalding hot are you saying the water heater temperature exceeds the engine coolant temperature?

Jon - I should have been more clear...the hot water in the heater matches the coolant temp, around 195 degrees.  Sometimes I'll see steam coming out from under the sink.

Stu - good copy on the thermostat...will do, thanks!

[Indian Falls]

My two cents:  I got way  more water shooting out the exhaust than 1 splash every 5 seconds, more like 1 splash every 1.5 seconds.

The hot water heater does not have a pressure release, that is a temp release.  Mine is marked 210deg max. The most pressure the coolant loop in the heater sees is marked on your "radiator cap" 14 or 16 psi. 

ok three cents:  You don't have an air bubble issue.  Airlocks cause immediate overheat,  not 4 hours of running at 165 then creeping up.  You simply don't have enough flow of seawater thru the HX to keep up with the engine.
This same water is supposed to douse all the heat in the exhaust.  Your water muffler and hump hose are probably too hot to touch.  Your temp gauge may be off a few degrees as well, being you're heating the potable water in your water heater beyond the temp rating of the release.

[Stu Jackson]

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The hot water heater does not have a pressure release, that is a temp release.  Mine is marked 210deg max. The most pressure the coolant loop in the heater sees is marked on your "radiator cap" 14 or 16 psi. 

ok three cents:  You don't have an air bubble issue.  Airlocks cause immediate overheat,  not 4 hours of running at 165 then creeping up.  You simply don't have enough flow of seawater thru the HX to keep up with the engine.
This same water is supposed to douse all the heat in the exhaust.  Your water muffler and hump hose are probably too hot to touch.  Your temp gauge may be off a few degrees as well, being you're heating the potable water in your water heater beyond the temp rating of the release.

Thx, Indian Falls.  From my earlier post:

There appears to be a recurring misconception about the freshwater coolant loop in some of these replies.

This is a binary issue:  either there IS or there IS NOT an air bubble in the line to the water heater.

If there IS an air bubble, the engine WILL overheat almost immediately because the freshwater coolant will not be circulating.  The pump cannot pump air, only liquid.

The "old" way to get rid of this air, whether because of changing the coolant, replacing the water heater or its hoses or any other reason that air gets trapped in that line, was to rev the engine while opening the petcock on the top of the thermostat.  Ron Hill's excellent use of a pump to purge the air by forcing it out is a marked improvement.  I do this but without a pump by simply disconnecting one of the hoses, raising it and pouring fluid into it until it drains out; same concept using gravity.  Maine Sail's use of an automatic air vent is more elegant, same concept.

In all cases, once purged, and the system doesn't have any leaks, the engine shouldn't overheat because of the freshwater coolant side of the house.

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That has been my experience and is consistent with everything I have ever read in our C34 Tech Notes about the way our engines (M25 and M25XP) operate.

I agree with Indian Falls that both you and Jon may need to investigate this "creeping" temperature rise AFTER the engine is burped, properly, because if the air bubble is not cleared by proper burping (by any of the three methods mentioned) the overheat WILL be immediate, not long term.  Notice that my first post said: "because of the freshwater coolant side of the house." 

It appears that the only candidate remaining is the raw water side of the equation.  Indian Falls nailed it.

And I think he and I would agree that if there is a leak on your freshwater side, you'd also have a problem, eventually.  Many sources for this possibility, HX tubes, hose clamps, etc.

[Jon W]

As I said earlier I no longer have creeping temperature issues since removing the "air bubbles" from the coolant circuit after removing the "airlock". Why didn't the air bubbles bleed out on their own? I have no idea, but they were in there. My engine now runs constant at just below 160 degrees.

[KWKloeber]

The hot water heater does not have a pressure release, that is a temp release.  Mine is marked 210deg max.
The most pressure the coolant loop in the heater sees is marked on your "radiator cap" 14 or 16 psi. 

For the sake of accuracy/safety, water heaters (I don't know about yours) *must* have a "T/PV" (temperature/pressure valve)  -- if yours does not then a P.O. removed it.  They are typically rated at 210 deg F and 120 psi pressure.  For instance, the Seaward WH instruction/installation manual states (in several places) that it has a T/P valve. e.g.,
ITEM MODEL NO. PART NO. DESCRIPTION
   2    ALL             73127     TEMPERATURE/PRESSURE VALVE

Thats's on the potable-water side.  Also on the potable water side, the pressure in the WH can far exceed what pressure your water pump can put out.  But on the coolant side, yes the max pressure would be the pressure cap rating.

There are check valves in the WH system and heating the water can increase pressure past 100 psi.  For that reason, the check valve on the WH cold water supply MUST be one that is rated for that use.  The OLD style, square-body, bolt-together Shurflo CVs are ok, the new ones are not:
https://c34.org/bbs/index.php/topic,8994.msg65100.html#msg65100

Sent: Wed Feb 8, 2012 12:27 PM
From: mailto:nnnnnn@Pentair.com
Subject: RE: Shurflow check valve

The old check valve with the bolts could handle more back pressure. The new one is sonic welded and can only take max 125psi max. Not good for water heaters they will develop a lot more than 125psi thermal expansion.

Shurflo Customer Service

[Jon W]

Derek, out of curiosity have you checked the rubber gasket/o-ring between the bowl and the body of your raw water strainer is in good shape and seated properly?

[waughoo]

Derek, out of curiosity have you checked the rubber gasket/o-ring between the bowl and the body of your raw water strainer is in good shape and seated properly?

I'm so pleased you posted this!  I took a look at my strainer today and discovered that it had NO o-ring present.  I have been having some trouble with temp management despite the system being rather thoroughly sorted since purchasing the boat.  At high RPMs, it is likely that some air might get sucked into the atrainer bowl reducing the amount of raw water at the heat exchanger.  I still havent determined if I have solved my problem, but this was one thing that was not correctly set up which is now sorted.  Thanks for the tip.

[Ron Hill]

Alex : That "O" ring is really a square rubber gasket, just like the one on your fresh water strainer under the galley sink!!

A thought

[Noah]

I would guess it depends on what strainer you have as what the gasket looks like. In any case, just make sure it is a tight seal when seated.

[waughoo]

On the first installation, it did roll out of place as I tightened it.  On the second try, it seated and held in place.

[Ron Hill]

Alex : I'm sure that you probably have the factory OEM strainers for the raw water and the fresh water systems.  I recently posted about the mesh size of the stainless strainer inside. 
The brand is a "Hypro series 3350 Polypropylene line strainer".  Catalina used the 3/4" size.  If you go on line you can find the strainer parts - cap, screen, bowl and gasket!!

A few thoughts

[waughoo]

I'll look into that.  The o-ring is working but the bowl and flange dont have any sort of recess to hold the oring.  The idea of a square rubber ring is likely to be the correct part.