Can barnacle-crusted prop cause overheating?

[scherzoja]

I'm hoping it was the 3/4" thick layer of barnacles on my propeller that caused the overheating today.

Boat hull is fine, new paint, nice and clean but prop is completely covered with barnacles.

Ran the engine today and it overheated. Elapsed time was about 40 minutes and overheated during last 15 minutes.

I also noticed that full throttle, in gear only got up to about 2200rpm (max rpm for this universal 5444 is 3000).

In gear (fwd) most of the time and noticed that the prop rotation noises were heavier-sounding and slight wobbliness.

Again, over heat was gradual and only after I pushed it up to 2000-2100 rpm for the last 15 minutes before I **** it off.

I then checked raw water strainer: clean
checked impeller: intact
Checked fresh water coolant: full

Recently cleaned out raw water system and freshwater system, so don't think there is clog there.

I swam down and cleaned off the prop, then restarted. Now, engine can exceed 3000 rpm in gear and there is way more prop wash.

I'm pretty sure the barnacles were the cause, but want to get confirmation that that hypothesis is possible. not looking forward to tearing trough the cooling system; I've got other boat things to do.

Anyway, let me know what y'all think
Thanks

[JPA Cate]

If it did not overheat when you ran it at speed, it was indeed the barnacle fouling. Next time you haul out, try some Prop Speed. It's really helped our prop (Flex-o-Fold 3 blade folder).

[scherzoja]

Thanks Ann,

Yes, when I ran it after cleaning the barnacles off, it did not overheat. I am not sure if there was trapped air in freshwater loop ( I recently changed hoses) or if it was the barnacles. Looks like it was the barnacles.

[Paul Annapolis]

Yes...all of that is possible--and likely but why did you leave out relevant and critical information about your boat and propulsion etc? And of course, the best way to find out? You did Clean the barnacles and hull and went for a ride. I had the same situation recently with a client with a 31' powerboat with a single I/O. And we went down the list..such as as it power or transmission? Did we get full throttle in neutral? You write "I'm pretty sure the barnacles were the cause, but want to get confirmation that that hypothesis is possible. not looking forward to tearing trough the cooling system; I've got other boat things to do." If you were "pretty sure" that was the cause--and you corrected it and it seemed to work, what is it you want us to tell you? And what other boat things would you possibly have to do before you would check and correct the overheating and propulsion problem???? BTW, you wrote that "I **** if off." LOL!!!

[Sailmonkey]

the barnacles caused the engine to overload.....and overheat.

[scherzoja]

Hi Paul,

Sorry about omitting important data. I was hot and itchy from fiber glass work earlier in the morning.

Anyway, here is the info.

2 blade fixed prop, 18" dia (pitch unknown)
Universal diesel, 5444 (44 hp)
Displacement is 17,000lbs, but might be irrelevant because engine tests were done at dock
Max throttle 3100rpm
Fresh and raw water systems recently cleaned and all hoses changed
Fresh water pump not changed, age unknown
Raw water impeller fairly new, not much use, still flexible and intact
In neutral,I did get 3000 rpm WOT
Only got up to 2200 rpm WOT in fwd
Didn't test reverse

The temp gauge had the following temp pattern over time
Rose from 0 to about 150 over 10 minutes, then dripped quickly to about 120 over about 90 seconds. ( I guess thermostat opened)
then temp rose steadily to about 165, where is stayed for about 20 minutes while rpm stayed around 2000
I then increased throttle and noticed that rpm rose slowly as I increased throttle and max throttle resulted in 2200 rpm (not normal)
During whole time, saw normal amount of raw water exiting the exhaust thru hull.

The engine and prop rotation sounded different from normal, much lower tones and engine didn't react as quickly to throttle increases, somewhat delayed, slow reaction. No hesitation, just slow.

The boat is tied up at the dock, never left dock

I noticed that the prop wash was not as violent as usual and the lines didn't seem as stressed as they usually are when I exercise engine at the dock. There was also not as much turbidity in prop wash. I thought maybe because water was higher than when I last ran engine.

There was noticeable wobbling feeling and noise when rpm was over about 1800, increased as rpm increased.

I suspected that, at the very least, barnacles had the prop out-of-balance, so I shut it down and hopped in the water to clean barnacles off. There were a lot of them.

In December, I hauled boat, cleaned and painted the bottom, as well as cleaned shaft/strut/prop down to metal, so it was all good and clean back then.

It was amazing to see how thick and large the barnacles were in just 7 months. Barnacles appear to prefer bronze over SS because, although the strut and prop were completely covered with barnacles, the shaft had mostly bare metal with a few, large barnacles, maybe 30% covered.

Anyway, once I cleaned barnacles off prop and shaft, I restarted the engine and noticed that it was much better. It reved up to 3000 WOT in forward and in neutral, the wobbling was gone and and the engine noise no longer had that lower-pitched noise that I had heard when barnacles covered the prop. Prop wash was much more pronounced with really cloudy prop wash this time.
Dock lines were much tighter this time around also.

I had thought I might have an air pocket in the freshwater coolant, and have not ruled that out yet, but it seems that the barnacles did have a large effect on the engine/prop performance.

If you think of any thing else to check, I'd like to get it running smoothly and eliminate any doubt I have in its reliability, especially with peak hurricane probability next month.

I heard that reving the engine might chase air pockets out of the fresh water coolant lines, any truth to that?

Paul, thanks for your help, i can't think of any more info to enter and I hope it was just a case of high barnacle density.

[scherzoja]

Sailmonkey, et.al.

Why did the barnacle growth on the prop cause engine to overload? was it the friction caused by the rough texture of the barnacles or the changed shape of the propeller (uneven barnacle growth)? I can understand the out-of-balance caused by uneven distribution of barnacles across the prop diameter.

Thanks

[Paul Annapolis]

Raw water intake may have been compromised. You did not say anything about the boat but the specs would suggest about a 36-40' sailboat. Sounds as if you have done what you were supposed to do. The simplest solution is usually the correct solution. Good luck!

[Sailmonkey]

Originally Posted by scherzoja

Sailmonkey, et.al.



Why did the barnacle growth on the prop cause engine to overload? was it the friction caused by the rough texture of the barnacles or the changed shape of the propeller (uneven barnacle growth)? I can understand the out-of-balance caused by uneven distribution of barnacles across the prop diameter.



Thanks

A clean prop slices through the water a heavily fouled prop become a rough rotating mass that takes lots more power just to turn on top of what it was designed to do.


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[senormechanico]

Why won't an airplane fly when it's been parked under a forest for 20 years and moss is growing from the surface of the propeller and every seam on the wings?

Same thing.

[scherzoja]

Damn Paul, you are good.

Didn't mean to keep you guessing, I knew I was missing something in the previous reply. It's a Pearson 367, an '82.

The PO had a large full-circle loop in the fresh water hose that went from the exhaust manifold to the heat exchanger. I always suspected that air was trapped in there, but never noticed any overheat issue. I corrected that a few months ago with straight-ish, slightly sloping hose when I flushed and replaced all hoses.

Paul, I'm sorry, I forgot to answer one of your questions, "... what is it you want us to tell you?"

I wanted to know if a barnacle-fouled prop can cause this overheating/overloading. Because I hoped it did and wanted to feel relatively sure that I didn't have some other, intermittent problem.

Sailmonkey, thanks for the info on the barnacle effect. It was an eye-opener to see what an impact barnacles had. I never realized it. I guess it's like driving on slowly deflating tires, you never know how poorly it is performing until you fill'em back up to specs.

Thanks again y'all. I'll run it again tomorrow to see if it overheats and cross my fingers that it was just barnacles.

[GILow]

I don't like the sound of the temperature dipping. That implies to me that the thermostat is sticking. The thermostat should gradually open (or close on some engines) as the temperature increases, making an asymptotic curve of the engine temperature as it approaches maximum operating temperature.

I'd check that out, since, from your description, maintenance has been a little light recently.

Matt


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[Cap Erict3]

Torsion from the imbalance and the increased surface area caused more friction.

Your tests defined the "what" the why will take experimentation under controlled conditions. I suggest moving on.

Polish something.


------------------------------
Looking for another pretty place to work on the boat.

[GILow]

As to the effects of a barnacle encrusted prop, not only can they cause overheating, but I actually lost reverse recently thanks to just a few small barnacles. We use propspeed with good results, but it was getting on close to two years a while back since we'd slipped the boat so it was losing its effect. I knew it had to be done, as i could feel the loss of power, but I got a big surprise when trying to reverse out of the pen one day, and instead we went slowly forwards. I thought the gearbox linkage had failed but on checking I could see the drive shaft reversing as it should.

To cut a long story short, I dived on the prop, scraped off maybe a dozen small barnacles and all was good again.

So why the loss of reverse? Well when you look at our prop aperture it is flat at the front with big scalloped curves toward the stern at the top and bottom. What I think was happening was that the barnacles were disturbing the laminar flow on the prop face (already super inefficient in reverse anyway, when you think about a prop shape) turning the whole prop into a big centrifuge blower with negligible reverse thrust. Meanwhile the water spinning out from the centre of the prop was hitting the faces of the aperture and being directed aft, hence we went forwards.

Wouldn't have believed it if I had not felt it happen, takes a bit of thrust to move a 17 ton boat too. Very glad we didn't run into the dock. Got a fresh coat of propspeed again now, so all is good for another 18 months.

Matt


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[JPA Cate]

GILow,

You describe only a few small barnies. I'm wondering if there's a current pushing you forward, or a breeze.....

A badly encrusted propeller will not work at all: I've seen one (a fixed 3 blade) that looked like a solid, sharp basket ball when the boat was hauled! Amazing. A light breeze blew him out of the pen, and he kept going backwards when he put the tranny to forward.

Cheers,

Ann
Ann