BMC engine questions

[stuart]

Hi, its been a while since I posted on here so happy new year to you all !!

 

 

 

My friends boat rebuild is coming near to going back in the water (see pictures here http://www.canalworld.net/forums/index.php...=0#entry325558)

 

The BMC engine used to be raw water cooled, after the rebottoming, a new skin tank has been fitted instead.

 

I'm after some pointers from you on how to reconnect everything up.

 

The gearbox also has (i believe) an oil cooler which used to have water pumped through it as well.

 

So question 1 is - which order do the: 1. engine, 2. skin tank, 3. oil cooler get connected up in ?

 

You can see the old water pipe running in the picture below...

 

 

 

Question 2: We need a new exhaust for the BMC - what's best? How to fit it?

Edited January 27, 2009 by stuart

[Eeyore]

Hi, its been a while since I posted on here so happy new year to you all !!My friends boat rebuild is coming near to going back in the water (see pictures here http://www.canalworld.net/forums/index.php...=0#entry325558)The BMC engine used to be raw water cooled, after the rebottoming, a new skin tank has been fitted instead.I'm after some pointers from you on how to reconnect everything up.The gearbox also has (i believe) an oil cooler which used to have water pumped through it as well.So question 1 is - which order do the: 1. engine, 2. skin tank, 3. oil cooler get connected up in ?You can see the old water pipe running in the picture below...Question 2:  We need a new exhaust for the BMC - what's best?  How to fit it?

The basic circuit is:

Thermostat housing to front end of water cooled exhaust manifold.

Back end of water cooled exhaust manifold to top of keel tank.

Bottom of keel tank to back of gearbox oil cooler.

Front of gearbox oil cooler to engine water pump (the one that shares the belt with the alternator).

 

Additional work:

Remove the existing rubber end caps from the exhaust manifold, and remove the tube stack.

Purchase new end caps for the exhaust manifold to suit the new/larger diameter hoses.

Purchase new end caps for the gearbox oil cooler to suit the new/larger hoses.

Remove raw water pump and associated fitting.

 

And the best advise is talk to other boaters to see this in practice; there is probably someone on here with a BMC who is near to you - just ask.

 

The standard type of exhaust uses theaded fittings, and is widely available at chandlers.

 

Steve

Edited January 27, 2009 by Eeyore

[RobinJ]

The BMC engine used to be raw water cooled, after the rebottoming, a new skin tank has been fitted instead.

I'm after some pointers from you on how to reconnect everything up.

The gearbox also has (i believe) an oil cooler which used to have water pumped through it as well.

So question 1 is - which order do the: 1. engine, 2. skin tank, 3. oil cooler get connected up in ?

 

Question 2: We need a new exhaust for the BMC - what's best? How to fit it?

There are a few options:-

1) Keep the raw water for oil cooling.

2) Coonect oil coolers in parallel.

3) Connect oil coolers in series.

It all depends on how you will be using the boat, canal cruising for short periods agaunst river cruising for long periods.

After some time (usually about four hours) the temperature of the cooling circuit will be at its highest running temperature, oil coolers connected in series can have a significant temperature difference between them. With the engine oil cooler, if the temperature of the cooled oil is high enough, it can produce a cascade effect, so the engine itself has to be cooled more to compensate, provided the skin tanks are large enough this is not a problem.

It is possible to connect oil coolers in parallel, but the size of the piping used and there location is important to ensure water flows through both simultaneously. This should ensure neither oil gets too hot.

In any event the usual order is Gearbox first, Engine second (this prevents an overheating engine cooking the gearbox too).

If you previously had a primary/secondary system, you will have to retain the Jabsco pump for the secondary (skin tank) circuit if don't intend to change it. Otherwise the shell will need to be removed from the exhaust manifold, a plug inserted into the cold feed connection and a blanking boot fitted.

 

For the Exhaust, is it fitted with a four bolt threaded flange and hull fitting?

If so it will take the relevant flexible exhaust fitting screwed to the silencer and hull fitting, fit everything from the outside inwards and wrap with bandage!

[stuart]

Theres no exhaust outlet on the boat yet so I'm open to options on what to fit.

[paulcatchpole]

Theres no exhaust outlet on the boat yet so I'm open to options on what to fit.

 

This may be an irrelevance for you, but when I bought my boat, the exhaust was in three pieces glued together with rust.

 

I made a pattern and Imran from Torqueflow created a TIG welded stainless replacement, in less than an hour while I waited.

 

 

Incredible service and a professional result - just a shame I can't see the shininess now it's covered in lagging... :-)

 

They're in Tyseley, since I spotted you're in the west mids.

 

PC

[stuart]

Okay, spent a couple of hours taking the old heat exchanger to bits over the weekend, here it is...

 

Now I'm assuming that I no longer need to use the heat exchanger, so I how will the plumbing run now? I need to get a couple of new end caps to replace the old ones with 40mm pipe that runs to the skin tank.

 

 

 

 

old raw water pump, this has now been removed.

 

 

 

 

Actually just re-reading the posts above... is this correct...

 

One end of the old heat exchanger is blocked up with new rubber boot (end nearest pump entrance)

 

The engine water pump connects (as present) from the end nearest the thermostat to the old engine heat exchanger (with exchanger removed).

 

The non-blocked end of the heat exchanger connects to the top of the skin tank.

 

The bottom of the skin tank, connects to the oil cooler

 

The other end of the oil cooler connects to the bottom of the water pump (currently has a 90 elbow fitted on it in the pictures above).

[RLWP]

 

Now I know why my header tank has those huge rubber endcaps. I didn't know that in some applications it had a raw water heat exchanger in it. Thank you for those pictures.

 

Richard

[turnbuttonboy]

Apologies for barging in on this topic but I have offered to put a temp alarm on a friends 1.5 BMC. He wants to keep the temp gauge as it is and the new alarm comes with a 3/8" NPT thread. Could anyone suggest where best to install it please.

 

Many thanks Giles.

[stuart]

Apologies for barging in on this topic but I have offered to put a temp alarm on a friends 1.5 BMC. He wants to keep the temp gauge as it is and the new alarm comes with a 3/8" NPT thread. Could anyone suggest where best to install it please.

 

Many thanks Giles.

 

You may be out of luck if you want to use both, but perhaps you could always put a "T" into the engine block to get both senders working together.

[Tony Brooks]

Apologies for barging in on this topic but I have offered to put a temp alarm on a friends 1.5 BMC. He wants to keep the temp gauge as it is and the new alarm comes with a 3/8" NPT thread. Could anyone suggest where best to install it please.

 

Many thanks Giles.

 

Perhaps change the thermostat housing (assuming its not raw water cooled) for one of the Metro ones that had the fan switch screwed into the top then search for an adaptor. I think they are the same as far as the studs are concerned. I think some cars had a distance piece under the housing that had the fan switch hole, but that would demand longer studs.

[turnbuttonboy]

Thanks for the advice - I should be having a look at it next week and it's good to have some ideas before getting too involved.

 

 

Cheers Giles.

[stuart]

Thanks for everyone's advice so far!

 

Now the next question:

 

On the starter, I've got 3 connections, a "large" negative a "large" positive which I assume can be connected directly to the starter battery, and another red/white wire which I'm thinking is the connection to the start button.

 

Can you confirm if this is correct and also what size cable I should be using for the start button and cable? Think the existing "fly lead" fixed to the starter is about 4mm square.

[MoominPapa]

On the starter, I've got 3 connections, a "large" negative a "large" positive which I assume can be connected directly to the starter battery, and another red/white wire which I'm thinking is the connection to the start button.

 

Can you confirm if this is correct and also what size cable I should be using for the start button and cable? Think the existing "fly lead" fixed to the starter is about 4mm square.

Be careful. On most starter motors, the large terminals are on the solenoid. One connects to battery positive, as you suggest, and the other connects to a short piece copper braid or bar which takes the current into the motor. There should be no external connection on this, and certainly nothing to the battery negative. The negative connection is through the mounting bolts to the grounded engine.

 

The exception is if you have a "proper" marine starter motor which will have a ground connection rather than being grounded through the mountings. Such beast are rare on canal engines, especially converted road engines like the BMC.

 

MP.

Edited February 10, 2009 by MoominPapa

[alan_fincher]

Be careful. On most starter motors, the large terminals are on the solenoid. One connects to battery positive, as you suggest, and the other connects to a short piece copper braid or bar which takes the current into the motor. There should be no external connection on this, and certainly nothing to the battery negative. The negative connection is through the mounting bolts to the grounded engine.

 

The exception is if you have a "proper" marine starter motor which will have a ground connection rather than being grounded through the mountings. Such beast are rare on canal engines, especially converted road engines like the BMC.

Good advice, but even if you have a converted road engine with no insulated negative, you may find that the starter motor has been chosen as a place to attach the negative feed to.

 

Here's a not very good (for seeing connections) view of ours, (on a BMC 1800, presumably very similar to the 1500).

 

On the pre-engage solenoid.....

 

The main positive feed from the battery is on the big left hand stud, (I wish I could work out how to insulate this point of potential big short circuits!....)

The right hand stud has a strap, (which you can't see) feeding the starter motor itself. (Ours is a folded solid copper affair, rather than braided).

The Lucar connector at the top is the activation from the ignition switch.

 

On the main starter motor.

 

The negative feed from the battery goes to a stud on the end. (Since this picture I've added another lead there to bond the negative to the hull - previously missing).

 

I think arrangements on BMC 1500 and 1800 are pretty generic, although the pre-engage solenoids do come with different terminations, (e.g all studs, no Lucar).

 

The solenoid, (which throws the pinion onto the starter ring, as well as connecting the starter itself) takes a lot more current than you might imagine. I've not measured it. but a heftier wire than ours has would be no bad thing.

 

[Rojja]

The solenoid, (which throws the pinion onto the starter ring, as well as connecting the starter itself) takes a lot more current than you might imagine. I've not measured it. but a heftier wire than ours has would be no bad thing.

 

It certainly does, I've measured ~40A initially fot the operate winding, dropping to ~3A for the hold winding.

A longish length of 'bell wire' can prevent the solonoid from pulling in.

 

Roj

[stuart]

Be careful. On most starter motors, the large terminals are on the solenoid. One connects to battery positive, as you suggest, and the other connects to a short piece copper braid or bar which takes the current into the motor. There should be no external connection on this, and certainly nothing to the battery negative. The negative connection is through the mounting bolts to the grounded engine.

 

MP.

 

Your correct, the BMC is connected like you suggest - I just skipped over the copper braid bit as I know this connects to the starter/engine block/negative.

 

Thanks