How can we prevent, diagnose, and eliminate overheating problems?

[tdonoughue]

Interesting. But the photos don't look like the slimy stuff that may be the 'white algae' parenthetical. Looks much more chunky. I wonder if that is not more scale buildup from the hardness/calcium in the water supply than a growth.

But, still interesting for the point that running frequently on the hose is not necessarily a good idea...

 

[WREKS]

@tdonoughue It is very soft. As it dries out it goes from translucent to opaque. See Post #14. As it dries further it becomes brown/grey.

 

[tdonoughue]

Yes, I have been following along. I guess I didn't blow up 14 as much, maybe, but even there it looks 'slimier' and here in the jackets it looks grittier. Same stuff, no doubt. And the fact that it goes from translucent to opaque to brown/grey does sound like AC slime. But the gritty quality in the jackets makes me wonder how much of that concoction is scale (or something similar) in the mix. There may be less of that component in lake water...

Don't have any answers here. Just making some observations and questing for knowledge...

 

[WREKS]

@tdonoughue Here is a progression of the stuff. It actually dries out and is easily pulverized. Bio-fouling of oil cooler drying out

 

[tdonoughue]

Fascinating. Would love to have some analysis of that stuff to see for sure. Just doesn't look like it loses enough volume to be just biomass. And like I said, the sandy/gritty quality confuses me. Every time I have encountered that slimy goo (AC systems, etc.), it dries to a brown coating that is rather smooth. Not that I have seen all that there is to see in this world, but that is where this has me scratching my head a bit. Must be something else in there too.

 

[WREKS]

I have also removed the port engine to check the cylinder head. If it appears there also, I will talk to a local lab or university to see if they can analyze it.

 

[Elliott]

I have also removed the port engine to check the cylinder head. If it appears there also, I will talk to a local lab or university to see if they can analyze it.

Be careful - they may identify a new life form, and your boat will become a protected biosphere under the the endangered species act. The government will then force you to preserve it by not using or selling it.

 

[WREKS]

Microbiological Control-Cooling Systems

 

[WREKS]

The terms 'Biofouling' and 'Biofilm' are more general terms for the slime that can build up in marine engines. I have been using the term 'White Algae,' but that would be more appropriate for commercial/industrial cooling towers that are open to sunlight. Thanks @swatski.

 

[Aquarius]

What is the best thing to do when an overheat alarm goes off? I had it happen periodically for no apparent reason a few times this summer, usually after running at 35-40 mph for 15-20 minutes with still having a healthy flow out of the pissers. What I would do is shut the engines off immediately (mostly to stop the noise of the alarm) and then wait about 15 minutes before starting up again and then it would be fine for the rest of the day, no matter how hard I ran it. I was wondering if it would be better to keep the engines running in neutral to keep cool water circulating through and just dealing with the noise from the alarm?

 

[WREKS]

I would do exactly as you did. Running while hot will create other problems.

 

[tdonoughue]

Yes, but I would do a normal shutdown. I would not advocate killing the engines while at speed (for one thing, you lose primary steering). Slow the boat to a safe stop, then kill the engines (during that process the engines will be at idle and circulating water to draw off heat). Then turn on the blower and open the hatch.

 

[Aquarius]

Yes, but I would do a normal shutdown. I would not advocate killing the engines while at speed (for one thing, you lose primary steering). Slow the boat to a safe stop, then kill the engines (during that process the engines will be at idle and circulating water to draw off heat). Then turn on the blower and open the hatch.

Thats what I did. When I would restart the engines after 15 minutes, water coming out would be scalding hot for about a minute which has led me to wonder about letting the engines idle or maybe cycle them on and off to keep cool water flowing.

 

[tdonoughue]

Well, that would be my advice. There is merit to the idea that idling keeps cooling water circulating. But it also keeps the ignition happening (e.g. the heat source). If you think about it, during normal operation, you always turn off the engine when it is hot (and the cooling water stops) and yet it cools down eventually. If you turn off the engine, your engine will do nothing but get cooler. If you leave it on, yes, the cooling water may catch up with the heat source. But then again, it may not--then you have a bigger problem.

 

[Aquarius]

Well, that would be my advice. There is merit to the idea that idling keeps cooling water circulating. But it also keeps the ignition happening (e.g. the heat source). If you think about it, during normal operation, you always turn off the engine when it is hot (and the cooling water stops) and yet it cools down eventually. If you turn off the engine, your engine will do nothing but get cooler. If you leave it on, yes, the cooling water may catch up with the heat source. But then again, it may not--then you have a bigger problem.

Makes sense. Now I just gotta figure out what causes it in the first place. Would be helpful if they put temperature gauges on these boats especially since it seems to be such a common problem.

 

[WREKS]

@Aquarius Have you boated in less than 3 feet of water and/or run aground or beached your boat-any of those circumstances can lead to overheating?

 

[WREKS]

Here is a cooling water flow diagram for the MR-1 engine. It may be helpful in explaining engine overheating. The labelling of parts is taken from the service manual.

The cylinder block water jackets tend to collect whatever the jet pushes into it and the cylinder head gasket keeps it from moving upward with the cooling water flow. Head Gasket flow allowance

 

[Aquarius]

@Aquarius Have you boated in less than 3 feet of water and/or run aground or beached your boat-any of those circumstances can lead to overheating?

I have but it was near the end of summer and I had already had it happen 3 or 4 times prior to the first time I beached. It only happened after cruising for 20-30 minutes straight at about 3/4 throttle when motoring to a destination. After the cool down, boat would run fine the rest of the day no matter how long I ran it. I have suspicions that it is just a faulty sensor

 

[WREKS]

@Aquarius That is a good place to start. It looks like the Engine Thermosensor is accessible in your boat. The service manual has the procedure for testing it.

 

[WREKS]

Updated diagram of cooling water flow for 2007 SX230 MR-1 showing cooling water pilot outlets