VP MB10A Overheating

[James W]

New boat, first day with time to have a little jaunt and although there was no wind I thought i'd have a little motor up the river.

Within a few hundred yards it was evident the old (1974) Volvo Penta MB10a was getting a bit too warm and so I turned back and moored up before the HT leads melted!

I'd had a good look at the engine when I bought her and it started well, went into gear ok, the oil looked clean, etc, etc and I had no reason to suspect any trouble. The previous owner told me the engine had been serviced and a new thermostat fitted (I have the old one in a box). However, on looking today at the fresh water filter, it looks dry and i'm not sure there's any water going through the engine at all.

I suppose it would be any number of the following problems:

Faulty intake seacock
Blocked inlet pipe
Salted up engine
Broken thermostat
Broken impeller/water pump

What do you think? Any suggestions would be really helpful please!

James

 

[VicS]

Check the quantity of cooling water being discahrged

I take it that it is a normal water cooled exhaust and that the cooling water leaves with the exhaust where it is visible but I notice that the owners manual shows a cock on the thermostat housing that can be set to one of two positions for wet or dry exhausts.

If in doubt about the total water flow check:

• the inlet ( external course strainer grid ?)
• the seacock ( gate valve ??) open ?
• the internal water strainer. If it is dry you may have to prime it in order to get it pumping water
• it has a water cooled MS gearbox ?? if so check that is not blocked
• the pump for wear of both the impeller and the interior. If you have run it dry you have probably wrecked the pump impeller
• the internal condition of all the hoses.
• The injection point into the exhaust

If all the above is Ok and there is a good total water flow check the thermostat for correct opening temperature. It should start to open at 60C I believe.

If you do not have an owners manual you can download one from

http://www.volvo.com/volvopenta/glo...ice/publication_search/publication_search.htm

Direct link if it works http://vppneuapps.volvo.com/ww/PIE/...403&d=Owners Publication&s=3681385&lang=en-GB

Parts lists and diagrams http://www.marinepartseurope.com/en/volvo-penta-cat-7742070.aspx

 

[James W]

No water from exhaust at all

Hi Vic, thanks for replying.

There didn't seem to be any water coming from the exhaust at all, and I kept going thinking that it would kick in at the magic 60 degrees but to no avail.

The cock on the thermostat housing was set to wet exhaust so I know it should have flowed through ok but it didn't.

I'm worried about the lack of water in the internal water strainer and why nothing's coming in. The problem is that i'm going to have to move the mooring next week to one that will dry on a hard base so I can have a look at the inlet for blockages and be able to spend more time fixing the damn thing. It's only a few hundred yards and i'll go with the tide but how much more damage could this do?

I'm already resigned to needing a new impeller and will buy one tomorrow.

Thanks,

James

 

[VicS]

Hi Vic, thanks for replying.

There didn't seem to be any water coming from the exhaust at all, and I kept going thinking that it would kick in at the magic 60 degrees but to no avail.

The cock on the thermostat housing was set to wet exhaust so I know it should have flowed through ok but it didn't.

I'm worried about the lack of water in the internal water strainer and why nothing's coming in. The problem is that i'm going to have to move the mooring next week to one that will dry on a hard base so I can have a look at the inlet for blockages and be able to spend more time fixing the damn thing. It's only a few hundred yards and i'll go with the tide but how much more damage could this do?

I'm already resigned to needing a new impeller and will buy one tomorrow.

Thanks,

James

I'd try to sort it out where you are. The trouble with running it with no water will be that you'll be running the exhaust system dry. You may already have done some damage there. Rubber hoses ?? Plastic water trap ??

You can check that you have water coming in by shutting the seacock, removing a hose and then cracking open the valve. If the strainer is below the water line then take the top off and see if it fills.

Once you have water coming in you can work through the system methodically, overhauling the pump as you go.

Check simple and low cost things first. Progress towards the more difficult or more expensive things.


Hopefully you will get some more replies. Not a common engine perhaps. It's the first time I can recall it being mentioned on here

 

[James W]

I'd try to sort it out where you are. The trouble with running it with no water will be that you'll be running the exhaust system dry. You may already have done some damage there. Rubber hoses ?? Plastic water trap ??

You can check that you have water coming in by shutting the seacock, removing a hose and then cracking open the valve. If the strainer is below the water line then take the top off and see if it fills.

Once you have water coming in you can work through the system methodically, overhauling the pump as you go.

Check simple and low cost things first. Progress towards the more difficult or more expensive things.


Hopefully you will get some more replies. Not a common engine perhaps. It's the first time I can recall it being mentioned on here

You're right of course, I'll have a go where she is and see what I can make out. I've already opened the strainer and then opened the seacock slowly to see if it filled but it didn't. I think the strainer might be above the water line though so i'll remove the hose from the seacock and start from there (very carefully)!

I might try and rig up an outboard to get me to the other mooring. I have a small one, just no bracket to mount for it on the transom. Any ideas?

Thanks for all your help Vic, it's much appreciated. The lack of knowledge about the engine might be because it's such an old one and most people have long since replaced?

All the best,

James

 

[alahol2]

If the strainer is well above the waterline you may need to 'prime' the system by pouring a bottle/bucket of water into the strainer until it is full. The impeller may be trying to suck air.

PS if the boat was out of the water when you tried the engine it's just conceivable that the previous owner has removed the impeller. I do when ashore.

 

[James W]

Of course!

If the strainer is well above the waterline you may need to 'prime' the system by pouring a bottle/bucket of water into the strainer until it is full. The impeller may be trying to suck air.

PS if the boat was out of the water when you tried the engine it's just conceivable that the previous owner has removed the impeller. I do when ashore.

I don't know what it is, but i'm normally a logical, systematic thinking bloke, but as soon as i'm on the boat, I seem to lose all common sense. What a complete pr*t i've been, of course the system should be primed!!

Whether that's the cause of the problem or not, I should have done that first and now i've probably ruined a perfectly good impeller for my stupidity. Lesson learned, i'll be buying a new impeller today and then will sork my way through the problem step by step.....starting by priming the system!

Thanks loads,

James

 

[Golf Charley]

James, if your problem is due to the system requiring priming because the strainer is above the water line, you may be better off lowering the strainer, as a tempoary measure to aid your diagnosis, and then think whether you should permenantly relocate it.

If flow through the seacock is restricted, try blowing air back through it with a dinghy pump, or water, by reconnecting your bilge pump discharge hose

 

[James W]

Sorted....I hope!

Got back to the boat today to try and begin to resolve the problem and started from the beginning for once, trying to be calm and systematic.

With the inlet seacock open I slowly primed the system via the internal strainer but the water kept disappearing. Thankfully I soon realised that it would always empty because the strainer is above the water line and so I closed the inlet seacock, slowly filled the strainer to the top, screwed the lid back on and opened the seacock again.

The engine started first press of the button and finally we had cooling water being discharged from the exhaust pipe!

I know i'm going to have to change the impeller before I attempt to go out again (after yesterday's running the engine dry) but touch wood it doesn't look like i've done any serious damage with the overheating.

One small question though, how much should be discharged? It wasn't a gush by any means but there was a good trickle, with a bit more now and again.

Thanks loads for all the advice as ever!

James

 

[Golf Charley]

The water will exit the exhaust in a series of gurgles and splurgles. It is designed to. Learn the exhaust sound of your boat, and immediately check for water flow, if your exhaust noise sounds a bit V8 or unsilenced

The rate of flow depends on engine size and RPM, as the impeller is driven by the engine, not an electric pump

Simplistically, if it does not overheat, its ok!

At idle, 5-10 litres a minute?

 

[James W]

The water will exit the exhaust in a series of gurgles and splurgles. It is designed to. Learn the exhaust sound of your boat, and immediately check for water flow, if your exhaust noise sounds a bit V8 or unsilenced

The rate of flow depends on engine size and RPM, as the impeller is driven by the engine, not an electric pump

Simplistically, if it does not overheat, its ok!

At idle, 5-10 litres a minute?

Thanks GC,

That's pretty much the way it is. I may well change the impeller anyway just to be sure as the engine did run pretty hot.

Really appreciate all the help,

James

 

[rfincher21]

Just bought an MB10A and seems to run pretty hot. How do you tell whether the seacock is in an open or closed position? It is not marked on the outside that I can see, and the lever is currently positioned between two places where it stops moving. I am guessing one place it stops is "open" and the other opposite position is "closed". I am afraid to move it from one position to the other while the engine is running. I bought the boat with the seacock lever in between those two positions.

 

[RMC]

Normal rule is that the seacock is open when the lever is in line with the valve/flow and closed when at 90 degrees or across the valve/flow.

 

[Dave_Seager]

Normal rule is that the seacock is open when the lever is in line with the valve/flow and closed when at 90 degrees or across the valve/flow.

If the handle is detachable this may not be reliable as the handle may have been repositioned. Sometimes there is a line on the end of the shaft which will be in line with the hose when the valve is open and at right angles when it is closed.

 

[rfincher21]

Here are three pics of the positions. The 1st pic is the position I found it in, the 2nd pic is what I think is closed, the 3rd pic I think is open. Do you think I can run the engine in all three positions without damaging it, just to find out what is open/closed? I've tried to remove the hoses, to get a visual of the inside of the valve - they aren't going to come off.

 

[James W]

Here are three pics of the positions. The 1st pic is the position I found it in, the 2nd pic is what I think is closed, the 3rd pic I think is open. Do you think I can run the engine in all three positions without damaging it, just to find out what is open/closed? I've tried to remove the hoses, to get a visual of the inside of the valve - they aren't going to come off.

Hi there, you are a bit stuck between the two positions of the tap there. That's not a seacock, that's the heat exchanger. The correct position if you want raw water cooling (sucked in from the sea/lake) then it should be a bit like position two, but actually in line with the exchanger, i.e pointing astern.

My engine ran hot because I hadn't primed the raw water system before starting the engine. You do have to make sure that the system is primed (my was via the raw water strainer) before you start the engine. Also, you need to locate the actual seacock (the through hull fitting) and make sure that that is open when the engine is running or the engine will run dry.

Sorry if i've stated the obvious here!

Good luck,

James