3JH4E Overheating at low RPMs - Any ideas?

[flightlead404]

Chugged down the ICW from Fort Pierce to Lake Worth yesterday in my new to me 2007 H38 and experienced odd overheating.

I cannot run over 1,700 rpm for any length of time (> 10 mins dependent on engine speed) without getting an overheat alarm. When the alarm goes on, a couple mins at low (1,100 or so) rpm resets it.

Almost continuous whisps of white out the exhaust which I believe to be steam not smoke consistent with overheating.

Luckily we had the headsail out most of the way and made 4.5-6.6 kts at 1,600 rpm.

I checked the sea strainer, clean. Impeller, new in Dec, looks great. No collapsed hoses, no kinks or otherwise obvious hose issues. There’s water spitting out the exhaust. No obvious water leaking from fresh water pump. V belt was rather loose, I tightened it.

Coolant tank a little above the “Low” mark with no oil in in. Oil nice and clean and slightly above the high mark (not done by me!). No air filter element in silencer.

Other than the belt, nothing obvious. I’m stumped.

Any ideas?

Now on the hook north Lake Worth hoping to sail to Port Everglades tomorrow.

 

[wouterdebie]

I had my 37.5 delivered this month and the delivery crew had a somewhat similar issue. After replacing all the filters and cleaning out the strainer, the engine would overheat above 2200 rpm, but water was coming out of the back, but also white smoke. Turned out that there was a clump of seaweed stuck in the inlet. Are you sure that the whole way from the inlet to the engine is clear?

 

[Brian D]

Cooling water has to run through multiple "tunnels" within the engine. No doubt that some of them are possibly blocked. I would first off, try running Salt Away through the engine's cooling ducts. Hopefully you have a flush connector on the engine. A friend of mine owned a Yamaha 33 and after each use would flush the engine cooling ducts with Salt Away.

Now, it is possible that this engine has internal cooling like a car radiator. If that is the case, then you still might need to flush out the cooling system.

One more thought, that would be to replace the thermostat.

 

[Ralph Johnstone]

Try removing the raw water hose just before it enters the mixing elbow and direct the hose into a five gallon bucket. Check the rate of flow once you start the engine. It should be in the neighbourhood of 4-5 gallons/minute. If it's not, check some more as to why the lack of delivery.

If it is full flow, I hate to say it but "fouled heat exchanger tubes". The tubes are coated with crap that insulates them from conducting heat

OR MAYBE

if the flow is low, fouled tubes could be the cause. Loss of cross sectional flow area.

Lots of things to look for as you dig deeper. Good luck.

 

[JoeWhite]

I wonder if it needs to be burped. Trapped air on the engine block.

 

[Ralph Johnstone]

On further thought, any chance of something in the line before the strainer (dead fish, small fish) ?

I know you're on the hook right now but if you don't ultimately come up with an answer, maybe try something like this:



Several years ago I was repeatedly plagued with crap and corruption getting stuck in the area of the thru hull valve. Re-piped the inlet like the above. When I had an overheating problem, All I did was unscrew the top plug and attach a 18" vertical clear vinyl hose (previously fitted with an adapter) in the top of the "T". I then passed a wire with barb down the hose and pulled out any junk that was stuck in there.

Of course, AFTER I installed that, it never plugged again. No justice.

 

[kloudie1]

Exhaust elbow clogged with carbon?
Restriction on he water injection point of the exhaust ell?

 

[jssailem]

When I did my sea trial, cruising in the bay above 2200 rpm I saw the temp advance rapidly. I backed off the rpm and headed back to the marina. The owner had his mechanic jump on the issue I got a call that they had found a blockage that would foul the heat exchanger as the rpm increased. They fixed the issue and I bought my boat.

You need to look at all the water paths. Many ways the cooling water might foul.

 

[Kings Gambit]

My Bavaria which has saildrive and the 3JH3e Yanmar will do that (pass steam out the exhaust) when kelp, plastic bags, or other obstructions get sucked into the raw seawater intake which has no screen. The stuff never makes it to the strainer. As others have noted, it gets stuck in the hose leading to the stainer, at the seacock, or in the lower leg for me. The first time (as a recent new owner) I had a guy come out who took off the hose at the intake seacock to reveal a plastic bag stuck there. Since then I’ve sucked up kelp as well which causes the steam, even though water is still coming out.

The remedy for me is to back-flush the intake hose leading to the strainer through that seacock to clear what might be in the leg of the saildrive. The first time after the plastic bag incident I accomplished that using the dock hose to flush out some kelp. As I could not use that method when away from the dock I rigged a way to back-flush using the manual water pump of the Jabsco head, which is in the correct spot to allow it. I’ve had to do it several times. Use the up-stroke to bring up water then divert it into the flush hose instead of putting it into the bowl with the down stroke. There is a surprising amount of pressure there. Enough to do the job, but it’s a bit messy with water. Should require only a few (3-5) strokes.

Be cautious running the engine when kelp is around the boat at anchor. Also, of course, avoid running through floating patches of kelp, even small ones. Trash run-off with rain brings many plastic grocery totes into the water. They float at just the right depth to be easily sucked in if you run over one.

 

[RoyS]

You should have a strainer on the raw water intake outside the hull. I foolishly took mine off one year and shortly after ingested a jellyfish that completely blocked the intake. Next haulout, I added a new outside strainer. Groco sells strainers that can be installed over your existing thruhull mushroom fitting or you can replace the thruhull fitting with one that includes a strainer. Joe White above suggests burping to remove any air trapped in the upper engine block. That needs to be done every time you replace your antifreeze. Worth a try.

 

[Kings Gambit]

You should have a strainer on the raw water intake outside the hull. I foolishly took mine off one year and shortly after ingested a jellyfish that completely blocked the intake. Next haulout, I added a new outside strainer. Groco sells strainers that can be installed over your existing thruhull mushroom fitting or you can replace the thruhull fitting with one that includes a strainer. Joe White above suggests burping to remove any air trapped in the upper engine block. That needs to be done every time you replace your antifreeze. Worth a try.

Yeah. Around here in summer there can be “blooms” of gelatinous zooplankton, like salps. They get sucked in and because that are delicate they “disintegrate” into a gel-like agglutination which clogs in the strainer. If you notice a lot of jellyfish, nettles, or other gelatinous stuff at anchor where you have been running the diesel for charging, check your stainer b/f you get underway.

 

[Ralph Johnstone]

I rigged a way to back-flush using the manual water pump of the Jabsco head, which is in the correct spot to allow it. I’ve had to do it several times. Use the up-stroke to bring up water then divert it into the flush hose instead of putting it into the bowl with the down stroke.

Absolutely brilliant.

This could be neatly piped from the head pump (I don't use the Jabsco word any more) with the required valves, and Teed into the engine cooling water tubing upstream of the strainer and provide an immediate back flush when and if needed. Not an easy job of running the tubing but worth its weight in gold in a tight situation.

I see that you have not yet patented this this idea . My Chinese contacts will be cranking out a cheap, wobbly, overpriced version of this attachment within weeks. My dreams of early retirement may come to fruition yet .

 

[Ralph Johnstone]

If you notice a lot of jellyfish, nettles, or other gelatinous stuff at anchor where you have been running the diesel for charging, check your stainer b/f you get underway.

You should have a strainer on the raw water intake outside the hull.

I guess checking the external strainer shouldn't be too much of a problem . Now, if you can just find your SCUBA gear, wherever you left it.

 

[jssailem]

And use rubber gloves. Those jellyfish, even smooshed in the strainer screen can still sting ya.

 

[Stu Jackson]

Dinghy foot pump connected to hose to inlet strainer.

 

[sail sfbay]

My Hunter 46 Yanmar engine had a similar issue when operated at very high rpm, during an engine inspection. Mechanic said it a slightly fouled heat exchanger that needed to be cleaned or replaced (not cheap). However, it does not run hot at my normal cruising rpm so I am deferring this maintenance until I plan a long trip.

 

[jssailem]

Clever set up. Did it work?

 

[sail sfbay]

Barnacle Buster, alternative to mechanical cleaning of seawater cooled equipment, was just recommended on Cruiser Forum. With minimal dismantling required, Barnacle Buster™ can be safely re-circulated through seawater cooling systems, dissolving barnacles, zebra mussels, calcium, rust, lime and all other mineral deposits Looks doable.

(33) How to Clean a Boat Engine Heat Exhanger using Sea Flush and Barnacle Buster - YouTube

 

[flightlead404]

I guess checking the external strainer shouldn't be too much of a problem . Now, if you can just find your SCUBA gear, wherever you left it.

Its in Atlanta.

I'm in Ft. Lauderdale, Pier 66. Decided I need to fix this before I press on.

I'm disinclined to get into this nasty water lol

 

[Stephen M]

Clever set up. Did it work?

Worked very well. I had used this method on a twin diesel engine power boat in the past. I have loaned out the "Cleaning Kit" to other fellow boaters where they may have had to pick up some fitting adapters to make my setup work.