BMC 1.8 engine temperature

[Grassman]

 

I've just had a new skin tank fitted. It's a long story as to why it was needed so I won't bore you with it, except for the fact that it was overheating previously (up to 100c and would be more if I hadn't eased off the revs). The issue now is that on canals (I've yet to try it on a river) the temperature doesn't go above 60c. So I'm asking you knowledgeable fellows if that's acceptable or not because I think I've read somewhere that an engine running at too low a temperature makes it inefficient and it uses more fuel and can even damage an engine over a long period. I presume this applies to any engine.

Is this true, and if so is there anything that can be done to increase the running temperature slightly? Somebody has told me that restricting slightly the flow of water into the skin tank might be an answer.

In a couple of weeks I'm going to test it out on a river because previously these were were the overheating problems were severe, although even at a sedate 3 mph on canals it was occasionally overheating when on open stretches. 

[alan_fincher]

The engine should have a thermostat.  Typical values used on BMC are either 74 degrees C or 82 degrees C.

Until the engine has got hot enough for the thermostat to open, then no water should be being circulated through the skin tank, so the size of the skin tank should be irrelevant.  Put simply, if the stat is present and working you can't have a skin tank that is too big.

I would suggest that either the thermostat is missing, (perhaps removed by someone in a wrong belief it could help deal with overheating), or is present, but failed in a stuck open position.

Open up the thermostat housing, (can be a pain if there is a very short hose to the header tank), and see what you have.  If present test it in hot water with a thermometer, to see if it opens in the range 74 to 82 degrees.  If not, replace.

Over-cooling will not be good for the engine.

Was your boat built by Mike Heywood or Evans and Son?

EDIT: Don't even think of artificially restricting the flow into your new skin tank!  That's just the wrong way to go, and with a correctly operating stat, it cannot be required.

Edited August 10, 2017 by alan_fincher

[WotEver]

As Alan says, the only thing which controls the engine temp is the stat. As it's running too cool the stat is either faulty or missing. 

Running too hot is a sign that something is amiss with the cooling system but too cool can only be the thermostat. 

[Tony Brooks]

Modern wax stats can and do leak wax when overheated so they do not open at the correct temperature. Some of the better/older designs had a catch system so when they "over opened" at high temperature the catch locked so it could not close. As above always worth a check.

That 60C rings a bell. I recall I heard/read somewhere that at least one mariniser fitted a 60 degree (probably 62C) stat to reduce the temperature of the water in the calorifier to a slightly safer level. personally I would not fit a stat much above 70C unless the domestic water had a thermostatic mixing valve to limit the temperature from the taps.

My Bukh runs happily with a 62C sat.

Edited August 10, 2017 by Tony Brooks

[Grassman]

Thanks for your help boys. The thermostat was replaced last year as was the temperature gauge and sender, but because the temperature was regularly getting up to 100c  perhaps it may have caused it to be faulty now (as Tony suggested)? I have to get somebody in to do any mechanical work and he is away on holiday until 28th so when he gets back I will get the thermostat tested and replaced if necessary. Callcut Marine say the only thermostat that can be fitted to a BMC is either a 74c or an 82c. Is that true and if so which one should I have?

In the meantime I want to use the boat for a short trip of 6 days on the canal and a day on a river so will it be alright to run at 60c without damaging the engine or should I wait until this problem is sorted?

Alan, the boat was built by Colecraft in 1995 and fitted out by Reading Marine.

[Tony Brooks]

Fit either thermostat, its your choice. As I said if there is a calorifier involved with no mixing valve I would always go for the lower one.

Has anyone actually checked the engine temperature with an infra red thermometer? Temperature gauges have an all too common tenancy to be inaccurate and lie - especially when US & European senders and gauges have been mixed up. They need to be matched and stay matched. If you mix them  they will either read about twice what they should or about half (very rough figures).

I think theory and the actuality are divergent here. The hotter you run the engine the more efficient it is but I doubt you will notice the difference in fuel consumption between 60 & 88C. Also the hotter it runs the more chance you have of driving any condensation out of the oil BUT canal boat engines run at exceptionally low powers for their size so the oil temperature is always likely to be lower than in a vehicle. the coolant thermostat will not effect this.

Stop worrying, go an enjoy the canals. Any potential wear you may cause will be so miniscule it will be impossible for anyone to tell it has happened. I'd rather take that very small chance than risk scalding my wife or guests.

[alan_fincher]

OK,

I only asked about builder as Mike Heywood , (aka Evans & Son), was notorious for unsuitable/undersized skin tanks. (we also had to have a new one built).  I have never (before) heard the same of Colecraft though.

Certainly Calcutt only supply 74c or 82c stat.  Their usual advice is fit 82c  if no calorifier, but 74c if there is, (to avoid skin removing temperatures from hot taps).  However as Tony suggests you may have a thermostatic mixer valve on the calorifier - if so I would go for the 82c stat, as you'll get an increased supply of hot water, as some of it will be cold water mixed in to reduce maximum temp.

If you are confident a stat is present, I can't see any explanation for cold running than that it has failed, (or part failed).  Nothing else fits the facts you have described.

I don't think you will do any harm running for a while at reduced temperature. You will. however, probably get far fewer showers out of the calorifier than you did when it was running at far higher temperatures though!

Edited August 11, 2017 by alan_fincher

[Tony Brooks]

It rather depends upon how long the OP runs the engine for when testing. If he has a larger, cold calorifier and is  only running (say) half an hour to test the cooling no wonder it has not reached temperature.

[bizzard]

He might be a bionic Cyborg made of asbestos and be completey immune to the higher heat.

Edited August 11, 2017 by bizzard

[Richard T]

We too have a Colecraft hull with a BMC 1.8 and the skin tank is too small. It has an area of about 7 sqft whereas the power of the engine indicates that it should be around 11 sqft. We intend to have a second tank added to the outside of the swim as access to put one on the inside is very difficult. We cannot run the engine at above 2000rpm for more than a few minutes without the temperature rising to above 90deg C. So we are not going to go on the tidal Trent and similar rivers until sorted.

[WotEver]

31 minutes ago, Richard T said:

We intend to have a second tank added to the outside of the swim as access to put one on the inside is very difficult.

The outside of the other swim, presumably?

[Tony Brooks]

He may be having a single large one welded onto the same side with pipe stubs fitted to the hull through the old tank.

[WotEver]

1 hour ago, Tony Brooks said:

He may be having a single large one welded onto the same side with pipe stubs fitted to the hull through the old tank.

He may, but he did say "second tank" which suggests that it's in addition to, not as a replacement to the old one. 

[Richard T]

To clarify the second tank will be on the other side to give us a total area of about 12 sqft.

[Neil2]

There's an awful lot of Colecrafts from the 80's and 90's with BMC 1.8's you think they would have figured out how much cooling they need.  I had exactly the same problem with a BMC in the last boat and it made any river journey against the current a nerve wracking experience.  But if we had kept the boat i would have changed the engine anyway...

[alan_fincher]

5 hours ago, Richard T said:

We too have a Colecraft hull with a BMC 1.8 and the skin tank is too small. It has an area of about 7 sqft whereas the power of the engine indicates that it should be around 11 sqft.

A lot better than our old Evans and Son boat "Chalice", that had only about 4 square feet, and, no internal baffles.  Also 4" thick giving hot water a good chance of avoiding the outer  surface cooled by the canal!  About as bad as you could "design" really!

For what it is worth we had a new external one made, baffled and thin, and the old one taken out.  The new one was 9.4 square feet, and proved entirely adequate with temperature always stayiny rock steady around the thermostat opening value.

Mind you it was only a 50 foot boat.

2 hours ago, Neil2 said:

There's an awful lot of Colecrafts from the 80's and 90's with BMC 1.8's you think they would have figured out how much cooling they need.  I had exactly the same problem with a BMC in the last boat and it made any river journey against the current a nerve wracking experience.  But if we had kept the boat i would have changed the engine anyway...

I suspect all engines of a similar power need a similar cooling surface.  Changing the engine surely only likely to help if you change to an air cooled one?

[Grassman]

Firstly. thanks Tony and Alan for your reassurances about my worries regarding damaging  the engine.

 

I tested the boat over two days between Atherstone and Fradley which included the 11 mile lock free section between Fazeley & Fradley Junctions where except for slowing down to pass moored boats, I was able to push it a little for quite long periods.

 

Last year when trying to solve the overhearing problem we changed the temperature gauge and the thermostat and sender unit in case it was a problem with those, and my man also tested the actual water temperature with an infrared device and it read the same as the gauge was showing so I'm pretty sure that is fine.

 

Interesting your comments about the calorifier and I will get this checked, and as I mentioned before, I will test and perhaps replace the thermostat because as Tony said in an earlier post, the constant overheating may have damage the old one.

 

In case this is relevant, after they fitted the skin tank, because they weren't sure of the amount of water in the system they guesstimated the coolant mix and it worked out to be only up to 12 degrees (the chap was leaving for his holiday and didn't have time), so when I got back to my mooring I put some more in and got it up to 22 degrees strength. Today I took it on a short run of 4 miles and 4 locks and the temperature was getting up to 5c more (65c instead of 60c). Mind you I'd have though that would lessen the chances of the temperature increasing?

It'll be interesting to see how it goes when I go on the longer trip in a weeks time as this will include part of the River Trent too.

 

 

 

[Neil2]

18 minutes ago, alan_fincher said:

A lot better than our old Evans and Son boat "Chalice", that had only about 4 square feet, and, no internal baffles.  Also 4" thick giving hot water a good chance of avoiding the outer  surface cooled by the canal!  About as bad as you could "design" really!

For what it is worth we had a new external one made, baffled and thin, and the old one taken out.  The new one was 9.4 square feet, and proved entirely adequate with temperature always stayiny rock steady around the thermostat opening value.

Mind you it was only a 50 foot boat.

I suspect all engines of a similar power need a similar cooling surface.  Changing the engine surely only likely to help if you change to an air cooled one?

Actually I don't think that is the case, but what I meant was I would have got rid of the BMC because I don't like the engine.  

 

[alan_fincher]

1 minute ago, Neil2 said:

Actually I don't think that is the case.

Why wouldn't it be?

[Grassman]

6 hours ago, Richard T said:

We too have a Colecraft hull with a BMC 1.8 and the skin tank is too small. It has an area of about 7 sqft whereas the power of the engine indicates that it should be around 11 sqft. We intend to have a second tank added to the outside of the swim as access to put one on the inside is very difficult. We cannot run the engine at above 2000rpm for more than a few minutes without the temperature rising to above 90deg C. So we are not going to go on the tidal Trent and similar rivers until sorted.

This is exactly the problem we were having with ours, and that Neil2 had with his previous boat, and it was on the tidal Trent where we encountered the overheating problems the most. This new skin tank has obviously done the trick. We had it mounted on the outside of the swim with the pipes routed through the old one thus rendering the old skin tank obsolete. The slight protrusion of the new tank has made no difference to the handling of the boat, it's just as good as before. 

I'm very pleased with the result (except my concerns about it now running too cold ) and it was after having read of Alan's experience with his previous boat 'Chalice' and his new skin thank that I decided to go ahead with my new skin tank. 

[alan_fincher]

Yours and Richard's experience has been an education.  I didn't until now realise Colecraft has a habit at some point of building inadequate skin tanks.

Similarly Chalice's handling was not noticeably altered by a thin tank added on one side of the swim only.

Out fabricator took the internal one out completely.

Goodness knows how the original owner had managed 10 yeras with a boat so prone to over-heating!

[Neil2]

20 minutes ago, alan_fincher said:

Why wouldn't it be?

What I'm getting at is I think the rule of thumb seemingly used by narrowboat builders is too simplistic in taking the manufacturers HP figures as a basis for calculating skin tank surface area.

Whether the engine is direct or indirect injection, whether the power rating is constant or intermittent, whether the rating includes ancillaries attached - it all makes a difference.  This is why proper marine engines like Bukh appear to need far less cooling than their marinised equivalents.  

[Tony Brooks]

8 hours ago, Grassman said:

 

Interesting your comments about the calorifier and I will get this checked, and as I mentioned before, I will test and perhaps replace the thermostat because as Tony said in an earlier post, the constant overheating may have damage the old one.

 

No need to even consider the calorifier because the test run you did was far more than enough to get it up to temperature. I fairly regularly come across people who think maybe 15 minutes running at not much more than tickover is enough to get their engine up to temperature. It may be without a calorifier but with a big one it takes far longer than that to heat the water so the engine heat is heating the calorifier rather than the engine.