A27FC Overheating not cooling system related?

[Jeremyvmd]

I would do some more diagnosis with a non-contact thermometer to check exact temperatures at various places on the engine and at the components including the oil cooler.

non - contact thermometers are essential kit IMO for any boater - pretty useful in day to day life too...lol

[kerrye]

Oh yes, essential in cooking perfect french fries in my opinion.

[denchen]

I do not know your engine, but another check, see it the diesel pump timing has come loose and the engine is running retarded (late). Just a thought...

[hetek]

You stated that you could get to the Lehman's redline of 4,000 while in neutral. Can you reach it (or near) while in the water, in gear?

I know you will be watching the temps climb as you do this, but if over-propping is a problem, this will tell. Just run it up, check the rev's and back it off before it overheats, if you can.

My A27's 4D61 would run all day at 3,000 rpm and 6 knots. It maxed out at 3,750 rpm and 8.4 knots - a bit shy of the 4,000 redline. I only tried the full throttle test twice - didn't want to hurt the ol' girl. BUT... when I ventured into the higher rev's, the temps did climb, but not to the point of overheating. Again, I didn't stay there too long to wait for a boil. It's been a while - I can't recall all the temperatures at RPM's.

Bob Smith at American Diesel worked at Lehman when they marinized the Peugeot 2112 cc diesel which is the 4D61. He told me once that Lehman did have some cooling problems with the engine after he left the company, with some engineers actually drilling bypass holes in the thermostat. He thought that was a poor idea though.

Good luck. I hope you nail it.

[hetek]

Another quick Bob Smith comment: There were two flavors of the Lehman/Peugeot 2112 cc marine engine. The well known 4D61 and also the 4D50, the latter is the 50 hp version which was created for the Japanese market. Really, it's just a detuned 4D61. There was no oil cooler on the 4D50. It was only used on the 4D61. Makes you wonder how much it was needed for those extra 11 hp.

[hetek]

Not to overthink this, but look at the performance curves for the 4D61 and the 4D50 in the Lehman Owner's manual in the "Documents" section of this site (Hmm... Wonder who contributed that?).

At your current sweet spot of 2,700 rpm, you're only using 45 hp. You are still in the "no oil cooler" territory of a 4D50. Not much further abover those rev's, Lehman felt the need for the oil cooler.

Again, not to go crazy, but you do have oil flow through the cooler, yes? Oil is a coolant too.

Just trying to help. I feel your pain.

[rnummi]

OK, Im gonna IR temp check the whole thing... Iv'e checked all the usual suspects... the only thing I havent done is remove oil cooler and boil/refurb same (I reverse blew it out and discovered my old impeller pieces parts). You are absolutely right about the intake(s). I keep kicking myself in the butt for not removing/cleaning same before the splash. Its the only thing conceivable left to check. The original hull was "barnacled up" when I bought it on the hard lending credence to JT's theory. (both Don and Ben will recall my swinging by home depot to obtain day laborers to climb under my rickety trailer to scrape off 6 year old encrustation) I also replaced all the filters with grocos... never thought to ream out/check the seacocks when on hard. Now a 2 second job becomes a giant PITA. Im either gonna have her pulled or find some soft mud to beach her and wait for tide to uncover ports.

Alternatively was going to swap hoses first to experiment. I've got Engine intake, Head intake, Generator intake, all in close proximity. If in fact I have microblockage in the intakes, I guess they would all be equally blocked though. $%$(%&*^&^ Maybe a swim with a coat hanger is in order as well.

Rick (kicking self in A$$)

[rnummi]

Not to go off topic, but the other variable was my Dad swinging by the boat while I was changing the oil and buying Mobile One synthetic 30-50.....to replace the old oil. Ive read the other threads concerning using "modern" oil vs. standard. Possibly related to the high rev overheat?

[Sprig1]

Hi my oil cooler on my 4d61 was half clogged when I removed mine. I was really quite surprised. Hope everyone had a good summer.

[Jeremyvmd]

Yea I assumed from your post you had checked the through hulls. I would check those next and see what they look like...can your marina do a short haul so u can check them real quick? Just have them leave her in the slings while u look then drop her?

[rnummi]

A good question... I use Salt Creek Marina in St. Petersburg FL... I'll have to check that pricing. I'm sure they do it.

[kerrye]

I would think you could check the thru hulls by closing them, removing the intake hose and replacing with a long hose hanging over the side of the boat and see if water sucked in that way keeps the engine cooler. It might save the cost of a haul out.

[Beta Don]

An oversized prop *can* cause overheating - You would be lugging the engine and there's not enough water flow to carry away the heat being generated. Same thing as trying to go up a steep hill in the Rocky Mountains towing a trailer with your truck in high gear at 35 mph - Downshift a gear, get the RPM's up with more coolant flow through the radiator flow and you won't overheat at that same 35 mph

In flat water, what's the maximum RPM you can (briefly) attain? If you can see 3500 RPM or so, the prop is not causing your overheating problem at 2800 RPM. The prop would be (about) correct and the problem is (despite the title of the thread) something in the cooling system

Since you sound quite sure you have adequate raw water coming out the exhaust, that can't be it - The clamshell inlet isn't plugged, the raw water pump is in good shape, the raw water side of the engine and oil coolers aren't plugged up in any way . . . . if they were, you wouldn't have all that raw water coming out the exhaust. What's left? The freshwater side of the cooling system. Assuming the fresh water pump on the engine is good (maybe a bigger assumption that you should be making at this point) and your coolant is the proper 50/50 mix of water and anti-freeze, then the next step would be to make sure the thermostat isn't causing the problem. If you've recently changed it, did you install it correctly?? - If it's in there backwards, it would cause exactly the symptoms you're seeing. Try running with the radiator cap off and look for evidence of good circulation of the engine coolant. If you don't see vigorous agitation at 2500 RPM, then you've found your problem - Either the freshwater pump isn't doing it's job *or* the thermostat is blocking the flow too much

If you do have good circulation, then it's probably not the thermostat or the fresh water pump. Probably time for using a good radiator flush product to clean up the freshwater side of the heat exchanger. That's probably a good idea in any case with a 35 year old engine which hasn't been run much for several years

Hope this helps,

Don

[TorreyWP]

I agree with those indicating a cooling system issue, you are most likely going to find a blockage of some sort.

It sounds like the entire raw water side of the cooling system has been properly back flushed and addressed. I am not completely familiar with the 4d61 but it sounds like you need to next address the closed side (coolant/antifreeze). I would look into descaling/flushing that entire side of the cooling system and then go with fresh antifreeze mixed appropriately. At the same time, it may be prudent to replace any hoses related to that system, I see that you have already replaced the raw water hoses.

Check the quality of the antifreeze in the engine visually and with a refractometer or hydrometer.

[tranmkp]

Here is a thought - send us a pic of your exhaust mixer. Where is the water being mixed/injectected? Bring your IR reader on a sea trial and open it up to flank speed. Take your reading. My A27 was over-proped when I got it, I ran it like a PT boat. Exhaust mixers are a weird science. They have to be done right. If you just poop around at low rpm its no harm, when you start red lining thats different. Exhaust velocity really increases and in a bad design it almost as if you had a dry exhaust. The header starts to really get hot (heat soak) and overwhelms the cooling system.

Red lining in the slip is useless, the water intake is in undisturbed water, it can really flow. Under way and going faster that hull speed (semi plane) that water flow is turbulent, atomised, its just not solid... so on top of mixer design, you are getting airated water flow. I know some will say "how do planing boats overcome that ? well, outboards maybe? A easy fix would be to make a modest sea chest and pull the undisturbed water off that. You would have to do some calculations for sure.

I am betting that this is what it is.

See my old boat at flank speed.

https://www.youtube.com/watch?v=0jOy4tJMhjs