M-25XP running hot + white smoke

[Derek]

Good evening everyone!  I bought my first boat, a 1987 C34, about 6 months ago and I've put her through the wringer with an ICW passage south, Bahamas cruising, and then back to the Chesapeake.  I'm embarrassed of all the stupid mistakes I made along the way, but the journey gave me a great chance to get really intimate with all of the boat's systems.  I can't put into words how incredible of a resource this forum has been in every respect.  Seriously, thank you!

Currently, my most pressing issue is that the M-25XP w/ 3" HX seems to be running hot and there is constant white smoke out the exhaust.  I've had two mechanics take cursory looks, and both said that the engine was running fine and there was no immediate concern, although neither could pinpoint the root cause.  I'm hoping you all might be able to give me some advice to help me troubleshoot the problem and work toward a solution.

PROBLEMS: 
1) Constant white smoke from exhaust, regardless of RPM or engine temp.  I hate to say that I slightly overfilled the oil about a half a centimeter over the fill line on the dipstick and it was two days later that I first noticed the white exhaust smoke.  Upon further inspection I discovered that oil had made its way to the bilge, presumably through a pressure release valve on the engine.
2) Cruising around 2700 RPMs, the engine will get up to 165 degrees and hold steady for a couple hours.  The temp will then slowly rise before it levels off around 195/200 degrees.  If I back down the RPMs or put it in neutral, the temp will go back down.  Maybe this is normal and expected once the hot water heater has absorbed all the heat it can, I'm not sure?

WHAT I'VE DONE SO FAR:
1) Raw water seacock clear.
2) Raw water sea strainer clear.
3) There was a hard 90 degree turn in the hose from the sea strainer to the raw water pump and it looked like the hose was slightly collapsed.  Based on a post from Ron, I installed a 90 degree elbow to prevent the hose from collapsing...that seemed to slightly improve water flow out the exhaust but did not impact the engine temp or white smoke.
4) Replaced raw water impeller, it was showing signs of cracks (I've got a Johnson water pump)...no impact.
5) Removed HX, cleared out a couple pieces of what seemed to be old impeller bits, and gave it a muriatic acid bath...no impact.
6) Blew out or replaced 5/8" raw water hoses...no impact.
7) Installed new vented loop on raw water line...no impact.
8 ) Cut out the rigid hose from the exhaust riser to water muffler and replaced it with a hump hose...no impact (the original hose didn't have any blockages in it).
9) Flushed the exhaust hose out with a water hose from the water muffler outlet to verify that it had good water flow and there wasn't a wasp nest or something in the exhaust hose.  Water flow was good...no impact.
10) Verified that I'm not losing coolant...the level is holding steady.
11) Verified that I'm not losing oil rapidly...I have to add a couple ounces every 50 hours or so, but I suspect that's normal.
12) The HX and coolant hoses are hot to the touch; the hot water tank gets the water scalding hot and will spit some out of the pressure release valve into the bilge.
13) Replaced the fuel injectors based on a mechanic's advice...no impact.

Apologies for the long-winded post, I'm just trying to be as concise as possible and not miss any details.  Anything that can help point me in the right direction would be greatly appreciated.

Thanks again!
Derek

[Noah]

I AM NOT a mechanic, but #11 and #12 seem unusual to me. However, I am sure you will get many responses from folks who are much more knowledgeable than me regarding engines.

[Jon W]

I have a 1987 with an M25XP and 3" heat exchanger also. Engine temp stays just 160F with sea water temp in low to mid 60'sF. I spent a lot of time purging the coolant circuit to get all the air out. The biggest challenge was the hoses to and from the water heater. Lots of air pockets in there. The only way to get the air out was with a hand pump and a 1/4" hose attached that I fished into each hose and drew the air out. Before doing this engine temp was normally 165-175F.

As part of your system and hose checks did you also verify the hoses to and from the water heater are clear and free of air?

[jmcdonald]

A problem I used to have was that after a hour or so of running in open ocean,
at 5 knots, the belt would start to slip, and the engine would slowly over heat
From 165 to 185. At the time I would back off on the rpm, and the temp would
stabilize at 180. Once back in the harbor, just putting back to the slip, the temp
would go right back to 165.

White smoke is usually steam and not from oil. Maybe some restrictions in the
heat exchanger or maybe some belt slip?

[Ed Shankle]

Derek,
Is there a normal outflow (subjective, I know) of water from the exhaust?
When you had the HX off did you check for blockages inside the nipple from the raw water inflow with a flashlight? I often get a buildup of salt/calcium that slowly closes it off. Need to break it up with a screwdriver.
Good luck troubleshooting.
Regards,
Ed

[Derek]

Thanks for the replies!  Let me try to elaborate on your questions...

Air block - when I refilled the coolant I used a hand pump to circulate the coolant from the thermostat hose to the coolant reservoir until the coolant flowed smooth without any air bubbles.  It did take some time and initially I didn't have enough coolant in the reservoir to prevent introducing new air bubbles into the system.  Topping up the reservoir did the trick and I pumped until I didn't see any more air bubbles.  I did not remove or check either of the hoses going to/from the water heater.  I'll add those checks to my list.

Belt slip - the belt looks to be relatively new and in good shape.  It was a little loose when I first bought the boat but I tightened it up to about a 1/2" deflection and it looks like it's holding well without any slip.

Exhaust outflow - I tried to find specifications for my Johnson water pump on how much outflow I should expect at certain RPMs but I struck out and couldn't find any info.  When I visually compare outflow with other boats around the same size, it looks pretty normal, maybe a bit on the low side...not steady or constant, but it'll blow out a bit of water every 5 or 10 seconds or so.  I'm considering replacing the Johnson pump with an Oberdorfer, but that's an expensive troubleshooting experiment.

Heat Exchanger - no blockages or calcium buildup in the HX.  I did find some calcium buildup in the vented loop and the hose from the vented loop to the exhaust riser combiner...I replaced both the vented loop and that short hose.

Thanks again,
Derek

[mdidomenico]

Exhaust outflow - I tried to find specifications for my Johnson water pump on how much outflow I should expect at certain RPMs but I struck out and couldn't find any info.  When I visually compare outflow with other boats around the same size, it looks pretty normal, maybe a bit on the low side...not steady or constant, but it'll blow out a bit of water every 5 or 10 seconds or so.  I'm considering replacing the Johnson pump with an Oberdorfer, but that's an expensive troubleshooting experiment.

i'm certainly no mechanic by any stretch and this might be subjective, but that outflow seems low.  i would expect a more frequent purge (not much, but a little)

some pictures of your engine compartment and undersink area might also help others spot something visually that might be out of place as well.

[Jon W]

You want to check the loop inside the water heater also so I wouldn't remove the water heater hoses from the water heater.

[Stu Jackson]

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.

Ed Shankle's advice is very good.  I had this issue when I first bought my boat and before I put in my 3 inch HX.  The inlet port was almost totally blocked.  But you say you did check it out.

Derek, I see no mention of replacing the thermostat.  Did I miss that?

Most importantly, where the hell did the oil in the bilge come from?  "...presumably through a pressure release valve on the engine." Sorry but you didn't explain how much oil.  Could it have come through the rw pump seals?  Rarely, as if never, have I heard of the oil breather letting enough oil come through to get to the bilge, it just doesn't happen.  And there is no "pressure release valve" on the engine that I know of, at least nothing called that.

Are you sure your pumping back through the 5/8" inlet hose cleared the actual thru hull?  Could it be partially blocked?

[scgunner]

Derek,

Let's keep it simple, you're getting steam from the exhaust because there's not enough water going through the cooling system. Less water means it has to do more cooling, which means it gets hotter, the hotter it gets the more steam is generated.

A bit of water coming out your exhaust every 5 or 10 seconds is not enough, or at least not normal. At low idle the exhaust on my boat squirts water about every 2 or 3 seconds, more when the RPMs are increased. You might try sticking your hand in the exhaust stream, it should be warm not hot. Hot is another indication of an insufficient amount of water going through the cooling system.

The cause of this is usually a blockage. Once I had a steam episode, under load I was getting more steam than the occasional wisp, I had cleared an earlier blockage (impeller vane) which improved the situation but not completely. Even though I was sure I had cleared the blockage I grudgingly went back and rechecked everything, sure enough I found another small piece at an elbow and guess what, no more steam. I'd start at the seacock and thoroughly check the system to the exhaust outlet.

[Noah]

In his first post he said "it makes white smoke whether it is both COOL or HOT"! So maybe it is not an overheating problem or it has multiple problems. Again I AM NOT a mechanic—but good at cut and pasting...

1. Clogged Fuel Filter

2. Incorrect Injection Timing (due to a bad injector pump, worn timing gear, or a compromised crankshaft keyway)

3. Low Cylinder Compression (due to compromised valves, cylinder glaze, or a worn or sticking piston ring)

These are all easily fixable issues.

White smoke coming from your diesel engine can also be a sign that water is getting into your diesel fuel and entering the combustion space. Commonly, this happens with faulty head gaskets or a cracked cylinder head/block. Unfortunately, if any of these problems are the cause of your diesel smoking white, they can be an expensive repair.

[Ron Hill]

Derek : Besides the items listed by Noah - Small quantities of water in the diesel will show as white exhaust smoke. 

Are you sure that there is no blockage in the raw water lines, no broken impeller blades in the pump elbows/cavity and a clean heat exchanger??  Has this engine always done these heating fluxions or just recently? 

Oil pressure relief valve? NO - oil pan vent Yes;  Hot water PRV Yes - and confirming that there is something in the raw water system that is restricting cooling!!

A few thoughts

[Derek]

Thank you all so much for all of the suggestions!  This will definitely help focus my troubleshooting efforts.  My next step will be to completely recheck every aspect of the raw water system from thru-hull to exhaust outlet to definitively rule out a blockage/restriction issue.

I used Ron's hand pump method when I refilled the coolant and I'm fairly confident it's not an air lock issue.

Stu - I did not replace the thermostat.  My thinking was that since I could watch the temp slowly rise and then hold steady at 165 for several hours, that the thermostat was doing its job.  But admittedly, I don't know much about thermostats.  Is there a test I could do to verify it's working or should I go ahead and replace it just to be safe?

As for the oil in the bilge...I'm not sure how much got in there, but it was enough to turn the water in the bilge black and send me into sheer panic (the bilge water was from the water heater pressure release valve).  Oil was spattered around the engine, e.g., on the alternator, the upgraded alternator bracket, the front of the engine and below it.  I couldn't identify from where the oil escaped the engine.  I drained the oil that night and gave it an oil change...there was no water or coolant mixed in with the oil that came out of the engine.

Ron - in the 6 months I have with the boat, the engine has always done this.  Holding around 2700 RPMs it'll heat up to 165 degrees...hold there for a couple hours...and then slowly start making its way up to about 195.  The water in the water heater will get scalding hot and will start spilling out the pressure release valve.  The previous two owners did not run the engine enough to replicate the issue, so it's hard to say when it started.  If I back down the RPMs or run it at idle the temp goes down.

Noah - awesome tips for the non-raw water related possibilities, thanks!  I'll go down that road after I double-check there's no raw water system blockage.

I'll post some pics and report back what I find next week.

Thanks again, you all are a wealth of knowledge!
Derek

[Jon W]

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

Stu, I tried all of those tips and tricks except the pressure pump method. They did get some of the air out of my system, but not all of the air and I was still getting some temp swings. Not until I fished the 1/4" tube into each of the water heater hoses, and put a ball valve on the top of the thermostat did I get all of the air out. No more temp swings as measured by the gauge, and my infrared laser, and runs cooler than before. I'm sure the pressure pump method would have worked, but it seems no matter how careful I am I end up with a coolant mess.

[Stu Jackson]

Stu - I did not replace the thermostat.  My thinking was that since I could watch the temp slowly rise and then hold steady at 165 for several hours, that the thermostat was doing its job.  But admittedly, I don't know much about thermostats.  Is there a test I could do to verify it's working or should I go ahead and replace it just to be safe?

Yes, take it out, read the T rating in degrees C, stick in a pot of water, with a thermometer, turn the heat on and watch to see if it opens at the right temp.

By the time you've done this and have the T off, just put the new one in.  If the old one works, keep it as a spare.

But buy two new ones anyway, just in case the old one has died.  Save a trip to the tractor dealer. 

Sometimes a friend will need one on a cruise and you can give him one.  Happened to me.