OverHeating

[Brad Young]

Here are the details.

1)Yesterday I changed the impeller, and pencil zinc. (first time)
2)ran the motor on the dock for about 1 hr, no problem, My engine
typically runs around 190.
3) went out for a sail, motored out to the Sea of Cortez, engine ran
another 45min or so.
4)sailed around for about 3 hours. Notice a storm coming and crank up the
iron Genny to head home.
5)within 15 min the high temp lite came on.
6)Check all my work and it look like it was OK.
7)Water was coming  out of the exhaust. However when it starting overheating
no water was coming out of the exhaust.
8)nursed DarBay home. Going to try and fix her today.


Questions
1)When I change the pencil zinc there was a lot of bits of corrosion. In fact the old zinc had nothing on it.Could this corrosion block a jet or port leaving the Hx
2)I would like to take the Hx exchange apart and clean it. However I have no spare parts for this. Is it possible reuse the o-rings and  gaskets.
3)Do you take both sides of the heat exchanger off? I have look around this site for a how to on the Hx. but could not find it. Internet connection is not the best.

Impeller
1)I remove the plate and it had water in it. So I think it is pulling raw water in.


Any ideas would be greatly appreciated

[horsemel]

I redid my heat exchanger this summer.  Lots of good information and help on this site.  You can buy the gaskets, again the information is on this site.  They cost only 3 or 4 bucks.  Yes both ends come off the exchanger.  It is one of the easier jobs I have done on the boat and if you search under hx or heat exchanger you will find all of the information you need and more.
Mark Mueller

[Stu Jackson]

You can re-use the end caps.  You shouldn't re-use the gaskets, but I have in the past in a pinch.  You can buy the gaskets and other parts from "Sendure" - do a search, it'll come up a lot.  One or more of the hits will have a photo of the HX with a phone #.  See reply #1 here:  http://c34.org/bbs/index.php/topic,3744.0.html

You'll have to BURP your engine after you're done, 'cuz taking off the HX will lose you some of the antifreeze.  Here's how to save the antifreeze before you take the HX off: http://c34.org/bbs/index.php/topic,4518.0.html

You're in Mexico: they can make anything there, so take a gasket to a shop and have them make you two or more - it's not rocket science or a special part, it's a simple rubber high heat gasket material.

Check the inlet port on the HX from the raw water pump which is where you are liable to find blockage from the salt dropping out of the cooling raw water.

Get rid of the parts of the old zinc that fell off inside.  Schedule a quarterly replacement of your zincs.

Finally, check your raw water intake.  See reply #2 here Sea Monsters!  http://c34.org/bbs/index.php/topic,4458.0.html

[Ron Hill]

Brad : From what you've said (good impeller) it sounds like you've clogged the raw water intake with something!

Close the thru hull and remove the strainer & bowl and make sure it's cleaned out.  Replace the strainer & bowl and remove the hose from the top of that assembly (thru hull still closed).  Slowly open the thru hull and you should get water coming in - that lets you know the intake is open.  If no water comes in, take a 3/8" wooden dowel and poke it into the thru hull and get it unclogged.   A thought

[Ken Juul]

Also check your impeller, it doesn't take long without water to ruin it.  It could be that you pinched the o ring.  That could also lead to a loss of prime.

[Indian Falls]

Same thing happened to me.  I had taken the caps off the HX and removed all the chunks of corrosion from the original zinc, removed 6-8 old impeller tips, Put in a new impeller. Cleaned the raw water intake screen and overheated when trying to come back in.

I found that after removing the impeller and putting it back in, blowing the raw water hose out to insure no clogs or bags in the intake that all it needed was some water in the radiator.

About 2 cups and I was off and running.   I'd checked the antifreeze coolant level only a few weeks earlier and it looked fine.  But somehow it got low enough that it would not cool the engine.

[Ron Hill]

dan : What you need to do to preclude having to remove the "radiator cap" to check the internal coolant (50/50 Prestone mix), is to install a coolant recovery system.  We've had numerous posts and articles written on the "how to".  A thought

[Brad Young]

The continuing saga.
1)Cleaned Hx (this really in increase the amount of flow of water in the exhaust)
2)flushed and added new antifreeze. Did not do a 50/50 mix.  I will redo on the next trip. when I replace the themostat
3) Cleaned and removed the screen the in salt water intake.
After running the motor for an hour the temp light comes on. However the alarm does not go off.
4)I now have a 15 degree difference between the gauge and the engine temp taking with a laser probe.  When I bought DarBay it was the same. Next trip I am going to go through and crimp all all the connections. 205 on the gauge and 190 with the probe.


Questions
1)Does extra resistance increase the value of the temp on the gauge.
2)Does any one have a part number for the radiator cap?
3)I have a themostat on order. I will replace it on my next trip down.
4)What is the normal operating range of a 25xp engine? With a 2 in Hx.
5)What temp does the overtemp light come on and alarm go off.

[Stu Jackson]

If you have a two inch HX, you have an M25 engine, not a M25XP.

The manuals have the parts lists of everything.  The exhaust manifold cap should be the same for both the M25 and M25XP.  Many have reported getting a 13psi cap from an auto store.  I have a parts #, but it's based on our local Universal dealer, and not a Kubota # so ti probably won't help you.

After you changed your antifreeze (freshwater coolant) did you burp the engine?

Operating temperatures depend on the thermostat you install, available in 160 and 180 models.  http://c34.org/bbs/index.php/topic,3133.0.html and http://c34.org/bbs/index.php/topic,3212.0.html

For the alarms and gauges, I suggest you get in touch with Seward.  While they only assemble the panels from Teleflex instruments and alarm board by others, they might be able to help.

[Ron Hill]

Brad : You say that you have 15 degree difference between the gage and your IR temp gun.  You didn't mention which was high - the gun or the gage?  I'd believe the gun, if you pointed it at the thermostate housing
Make sure NONE of the metalic sound proofing is touching that temp sender wire connection - when the steps/cover are replaced!!
Let me try to answer your questions:
1. Not too sure , but believe that increased resistance increases the temperature.
2. The cap is a standard 13PSI cap (available at any auto parts store)
3. The OEM thermostate is the 160 degree, not the 180 degree
4. You have a M25 engine , NOT an M25XP.  The temp should be about 160- 165 degrees.  Stu is correct in asking if you burped the coolant system?  Also the temp will probably change a little from water to 50% water/prestone!!
5. Not too sure which alarm system you have, but if you have the "dog house" shaped PC board on the temp gage(back side), it should go off at about 205F.

Hope this helps 

[Brad Young]

1)here is a pic of the alarm circuit board that is on DarBay. Is this the Dog House shape that you mentioned?
2)Can this board be replaced?
3)I have burp the line going to the Hot Water tank.
4) I am getting a 15 degree difference between the IR thermometer and the gauge. 185 for the IR and and 200 for the gauge.


I am going to check all the connection this weekend

[Ron Hill]

Brad : You've got the "dog house" type hi temp alarm.  It changes analog to digital and when the analog needle passes 200/205 degrees it will trigger the alarm to sound.  It was made by Bristol Marine which was predecessor to Seaward building the engine panels.

To check this alarm just turn ON the key switch and take a jumper wire and touch ground to sender.  That will cause the needle to go up and the alarm should sound.  
I wired in a spring loaded toggle switch, so I have a "press to test - hi temp" switch on my engine panel - press the toggle, the needle moves and the alarm sounds.  A thought

[Stu Jackson]

I haven't been able to hear that buzzer, except for before the engine turns over and after it's off, for years.  Probably ever since that New Year's Eve Party that I only wish would happen again and again.

We simply got into the habit of checking the temperature gauge regularly.  Just like tightening the wheel nut.  Remember, this is from the guy who uses engine hours for a fuel gauge.  

Your boat, your choice.  

[Ron Hill]

Stu has the surefire method - which is to constantly scan the engine instrument gages (just like we did when flying) !!  However, the only real
hi-temp situation that we've had on APACHE - was when someone else was at the wheel!! 

The alarm alerted the wheel person to ask me the question - "what's making that noise". 

I'll use all of alarms and help I can get!  A thought

[Stu Jackson]

No wonder no one will come sailing with me - I make 'em work!