Freshwater to Salt-engine temp inc

[Porchhound]

Visiting with the seller of a Tollycraft 34 just splashed in salt water.
Twin Detroit Diesel 4-53T engines immediately began heating up when he increased speed from 7kts to 9kts (normal cruising speed). He has replaced coolant/impellars. No sea strainer on either engine but exhaust discharge of water appears to be normal.

If this sounds serious I won't bother with offer/mechanical inspection. Any ideas?

Thanks in advance for any assistance.

 

[rslifkin]

Sounds to me like something is either clogged and restricting flow, or the heat exchangers are dirty and in need of cleaning. It's likely something simple, but I'd want the seller to figure it out and fix it. Or I'd discount my offer significantly (depending on what the mechanical inspection finds) to account for needing to go through the cooling systems.

 

[Chuck34]

What was the temp at 7 and at 9?
What temp T-stat is being used?

Since the engines have coolant, they are fresh water cooled. Are they full FWC with the manifolds included in the coolant loop?

 

[Porchhound]

Good questions I don't have the answer to yet. I'll check with the owner. According to him the temp increase wasn't happening when he was in freshwater. Not having sea strainers, my first thought was he got into something blocking his intake, but he seems to think his seawater discharge rate is normal.

 

[Nick F]

The fact that both engines are suffering the same problem is a good clue. Look for something in common with both engines. Do they share the same raw water intake?

 

[Porchhound]

I just got more info from the owner. During a sea trial the boat had both props/shafts, and the rudder damaged. Small damage to the hull patched and reglassed and both shafts and props replaced.

 

[fgarriso]

I just got more info from the owner. During a sea trial the boat had both props/shafts, and the rudder damaged. Small damage to the hull patched and reglassed and both shafts and props replaced.

Replacing the props and shafts should have nothing to do with the overheating issues. I would tell the owner to resolve the problem before going any further.

 

[Cigatoo]

Are you sure there is a problem? You haven't supplied any hard numbers / temps. Its very normal for a diesel to run on the cool side until under a good load. Increasing the load will "heat up" an engine to normal operating temp. What is the operating temp when it is "heated up"? If both engines react in the same manner it could easily be a normal condition. If you put the throttle (s) on the pins will they O heat?

 

[Lepke]

Besides simple issues like sea cocks not fully open, recent disintegrated impeller plugging heat exchanger, etc.

Any exhaust smoke? Color.
If the boat ran aground and damaged the running gear, alignment could be off causing the engines to struggle, injectors to supply more fuel, exceeding rated HP and causing black smoke.
If no smoke, especially black, then I would suspect marine growth in the heat exchanger or other parts of the raw water system. Could also have coolant side issues, especially if coolant is used for heating and connected between engines.
Normally a 4-53 is a very reliable engine, more so than the usual yacht engine.

As a buyer, I'd expect the owner to solve the problem before going on. Too many expensive repair possibilities and unknowns.

 

[Comodave]

Visiting with the seller of a Tollycraft 34 just splashed in salt water.
Twin Detroit Diesel 4-53T engines immediately began heating up when he increased speed from 7kts to 9kts (normal cruising speed). He has replaced coolant/impellars. No sea strainer on either engine but exhaust discharge of water appears to be normal.

If this sounds serious I won't bother with offer/mechanical inspection. Any ideas?

Thanks in advance for any assistance.

Immediately began heating up to what temp? Have you checked the engines with a non contact thermometer? It could be a gauge issue. It could be a restriction in the cooling circuit, could be a lot of things. I agree that the owner should be tasked with resolution of the problem before you proceed. He will have to fix it no matter who he sells the boat to so he might as well do it now.

 

[SaltyDogg]

The fact that he does not have sea strainers would make me first look at the inlet to the heat exchanger and see what/if anything is clogging it.

 

[Juliet 15]

Im not a marine biologist so excuse my ignorance: is it possible there were freshwater things in the cooling system that were killed by the immersion in saltwater, and now they've blocked your exchangers? As an aside, a sea trial the resulted in that much damage would scare me more than high Temps. I'd be doing some serious looking at the repairs there.

 

[kapnd]

Were the propellers replaced with same dimensions?
Overpropped vessels often do well at lower speeds, but temps jump at higher speeds.

 

[C lectric]

No reply so far from Porchhound.
I agree that you need to find out and post the actual temperature it was running at and then went up to. At just off idle and the engine run for a short time the temps may have been low from lack of load.
When the throttles got pushed up it would be natural for the temps to rise .

THe question is how much and to what level. You have provided NO specific info for opinions.

I have posted my tome below for both you and the owner to go through. It may help.

However, if the boat was truly overheating it is his problem to take care of repairs.

 

[Porchhound]

I didn't reply because I have no more info to provide other than the two posts. Lots of good advice, especially having the issues resolved before an expensive survey.

I posted the question more for the benefit of the young man trying to sell the boat. I get the impression he wants to do an "as-is" sale which would seriously discount his asking price.

Thanks for all the advice I will pass on.

 

[C lectric]

OK, Understand.

 

[John R M]

Just curious but if he's selling it, why is it going from fresh to salt water, seemingly for the 1st time?

 

[Porchhound]

Job change and relocation from Oregon is my understanding.

 

[Chuck34]

Even with an “as is” sale, get a survey with sea trial. If the owner balks, walk away.

 

[Porchhound]

Absolutely, Chuck. It cost me a few hundred dollars but I've already dodged a bullet after a survey of a CHB.

 

[bgillroy]

Typically the out of water inspection is followed by the sea trial. So when surveyor made his report what did he say? The surveyor would document operational variants to specs.

 

[bgillroy]

Buying an expensive yacht without a competent survey is great way to step in xxxt.

 

[Porchhound]

There has been no survey as far as I know. It never got that far with me due to the grounding and temp issues.

 

[BruceK]

There has been no survey as far as I know. It never got that far with me due to the grounding and temp issues.

But someone else had a sea trial (sometimes combined into survey) causing significant damage,and did not buy.
You don`t want to spend your $ diagnosing his problems but if you reach an agreed price(subject to everything) a mechanical survey before paying for a general survey might be an idea.

 

[Porchhound]

Excellent point, and less expensive. Thanks.

 

[NoRain]

You said in the original post the owner replaced “coolant/impellars (sic)”. First thing I’d suspect is an airlock in the coolant.