Changing Raw Water Impeller

[PaulN]

I currently have the seacocks turned off, with the raw water system full of antifreeze premixed and I want to change the impeller as it's 2½ years old. If I take the cover plate off, will I lose all the antifreeze or just a little and would it matter in any case. Also if this leaves an air pocket local to the impeller, does it self prime when the seacocks are opened and the engine started. The engine is a Beta 38 HP BV1505 (page from manual attached).

Another thing I've wondered, is how does the closed circuit water system pump and circulate to the heat exchanger to let the raw water do it's job and is any form of maintenance ever required.

Looking forward to hearing from you experts out there, particularly the one who's name begins with V. 

Pages from Beta 38 HP BD1005 Impeller.pdf

[MargeandParge]

If it was Marge doing the job she would leave the impeller till it came to de winterise and also keep the old one as a spare because they last a lot longer if kept wet especially with corrosion inhibitors. Still that's just the Ladies finding an easy way to the same result 

Festive Regards Marge and Parge 

[Meantime]

I personally wouldn't change the impellor until you're about to run the engine again. In fact I'd probably run it and get rid of the anti freeze, then change it. Leaving an impellor sitting in the same position for a long period doesn't do it any good, one of the reasons I don't  Winterise, then I can just turn the engine over each time I visit, even if not taking the boat out. Most impellor kits will come with a little sachet of lubricant gel which you should liberally apply to the inner casing of the pump and the edges of the impellor. This will lubricate it for the first few spins until it self primes. Impellors burn out very quickly if run dry. If you change the impellor now I suspect that lubricant which is water based would dry out by the time you start the engine if you were planning on not starting it until the start of the season.

The closed circuit water pump shouldn't need any maintenance. They normally have a metal fan to circulate the water.

[BroadAmbition]

and I want to change the impeller as it's 2½ years old.

Not before time then! - That's risking it somewhat.  I change ours out for a new one every 750 x Hrs whether it is showing signs of wear or not.  The one I remove then becomes the spare back up for the next 750 x Hrs

will I lose all the antifreeze or just a little and would it matter in any case.  You will only loose a little and no it doesn't matter but if you worried add a little more full strength into the raw water side 

does it self prime when the seacocks are opened and the engine started - Yes it will, just keep it on a fast idle till you see river cooling water exiting from the exhaust then your fine to go

Another thing I've wondered, is how does the closed circuit water system pump and circulate to the heat exchanger to let the raw water do it's job and is any form of maintenance ever required.

You have nearly answered your own question there  =  via the belt driven water pump that circulates the glycol laden engine coolant internally around the engine and through the heat exchanger.  Every major service it is a good idea to remove the heat exchanger stack and give it a good clean out.  At the same time drain down the engine coolant and replace it with fresh that's 750 x Hrs in your case, also check the condition of the internal sacrificial anode, if you have a strong enough mix of engine coolant it should be fine

Hope the above helps

Griff

 

Griff

[Vaughan]

43 minutes ago, PaulN said:

Looking forward to hearing from you experts out there, particularly the one who's name begins with V. 

I dare to hope that this compliment might be aimed at me?   

 

All the above posts are quite correct but they also show that there are two schools of thought :

1/. Do I change the pump impeller every spring?

2/. Do I remove the impeller in Autumn, after winterising and then re-fit it in spring, so long as it is not damaged?

 

First thing you need to do, is winterise the system and nowadays we usually pump antifreeze through the raw water system before finally stopping the engine.  After this, you can remove the pump impeller and store it for winter.  If this means you lose a bit of antifreeze, who cares?  You are going to pump it all away when you start the engine in spring, anyway!  In spring, you don't need to fit a new impeller if the old one is in good order.

This is just personal, but I don't trust the little sachets of lubricant supplied with a new impeller.  I always use a lot of specific water pump grease, such as Morris, which must also be spread on both sides of the face plate paper gasket.  These pumps are self priming but they rely on a good seal between the impeller and the pump body.  The grease is important in maintaining this seal.

Griff, being ex R.N., believes in "preventive maintenance", which means replacing a part regularly, before it is likely to wear out.  A lot of boatyards renew their impellers every year as a routine and nothing wrong with that! 

All the same, the most damage to an impeller is when it is left in the pump over winter and the vanes which are bent over become brittle.  Next spring when the engine is run, they will fracture and snap off.  So if you take the impeller out when winterising and you find it is in good condition, you can indeed continue using it for 3 seasons or more.

A lot of this also depends on water quality.  If you are running a lot in muddy, silty water, this will wear the impeller, as well as the pump itself.

 

[MargeandParge]

The raw water system has to re prime its self every time you clean the weed filter as the level will drop back to the water line on the intake every time the seal is broken. 

If its a good job it should pick it up on tick over.

Our routine start engine check oil pressure and ignition light then to the exhaust constant flow of water for 30 seconds and we are happy .

Festive Regards Marge and Parge 

 

 

[PCL023]

That’s got me thinking 🤔. Bought our boat back in 2010. Had the raw water pump on the list of things to change as the old one, (still installed) would need packing out and one of the old type grease glands had it’s treads stripped. Engine servicing is regularly carried out each year, however I have never changed the raw water impeller or removed it. There’s always a good flow of water out of the exhaust, so never really felt the need to fiddle with it? (The impeller). We have a spare on board if ever needed. In some 40 or so years of boating it’s not something I have ever paid too much attention to as long as there is a good flow?

I think I will add it to the list of de-winterisation updates as 12 years may be pushing it? 😜

To be fair it’s not something it have ever heard of folks doing? 

[Vaughan]

4 hours ago, PCL023 said:

To be fair it’s not something it have ever heard of folks doing?

It sounds to me as though you have one of the older Jabsco pumps with two grease caps on the pump shaft and driven by a belt?  On a BMC 1.5 engine I assume?

In which case it is a much smaller pump with only 5 or 6 vanes on the impeller.  These do last a great deal longer, and were only changed for larger ones when they started using the Bowman heat exchangers.  So it will last a lot longer, but you may have trouble preventing the shaft from dripping all the time.

[Vaughan]

4 hours ago, PCL023 said:

would need packing out and one of the old type grease glands had it’s treads stripped.

It is important to make sure that the pump is adjusted properly on its mounting to ensure that it is exactly aligned with the drive pulleys.  Also that the belt tension is not too tight, as this will put a side load on the pump shaft and cause wear of the gland.  You should almost be able to slip the belt off the pulley with your fingers.

You know, I never thought I would find myself talking about raw water pump pulleys on Christmas Morning!

Happy Christmas everyone!         

Edited December 25, 2022 by Vaughan
happy Christmas!

[Smoggy]

One of my raw water pumps is a sod for NOT self priming (the other one is always fine) so do be aware of water flow, if there's air in the system they are not guaranteed to self prime, my weed filters are above water line and level with raw water pumps so I leave seacocks closed and fill the strainer bowl and give the engine a quick spin first to check the level drops before topping again and replacing the lid, then open the seacock and fire it up.

Mine are VP not BMC of course, I've never got to the bottom of the one that does not always prime, I've swapped pumps from side to side and fully rebuilt the pump including machining the rear face and fitting a jabsco wear plate but it's still the same one that plays up.

[annv]

Hi Just to add what Vaughan said when you refit the impellor make sure that you bend the lob's in the right direction and a little grease smeared on both sides of the gasket and screw threads when reassembling. John

[MargeandParge]

5 hours ago, Smoggy said:

One of my raw water pumps is a sod for NOT self priming (the other one is always fine) so do be aware of water flow, if there's air in the system they are not guaranteed to self prime, my weed filters are above water line and level with raw water pumps so I leave seacocks closed and fill the strainer bowl and give the engine a quick spin first to check the level drops before topping again and replacing the lid, then open the seacock and fire it up.

Mine are VP not BMC of course, I've never got to the bottom of the one that does not always prime, I've swapped pumps from side to side and fully rebuilt the pump including machining the rear face and fitting a jabsco wear plate but it's still the same one that plays up.

Try  sticking a hose down the inlet with the sea cock open as we have known the stranger to have debris between the Hull and the outside of the strainer.

Festive Regards Marge and Parge 

[PCL023]

20 hours ago, Vaughan said:

It sounds to me as though you have one of the older Jabsco pumps with two grease caps on the pump shaft and driven by a belt?  On a BMC 1.5 engine I assume?

Yes it is installed on to a 1.8 BMC. 😊

20 hours ago, Vaughan said:

Bowman heat exchangers

It’s got a Bowman heat exchanger. It’s well aligned and the belt looks to be as you mention. 👍🏻. Looks a little loose but runs well etc. 

 There has always been a slight weep from the pumps shaft at times, I was thinking of changing over to one of the sealed pumps, I think Johnson do one that is almost a straight replacement, may need to enlarge the diameter of the pulls or replace it? All sounds great but have learnt for one reason or another, nothing that done on a boat is easy, even when it should be. 🤔😜😂. 

Will have to have a look next time. 👍🏻

Cheers Paul. 

[Vaughan]

7 hours ago, PCL023 said:

I was thinking of changing over to one of the sealed pumps, I think Johnson do one that is almost a straight replacement, may need to enlarge the diameter of the pulls or replace it? All sounds great but have learnt for one reason or another, nothing that done on a boat is easy, even when it should be.

It is possible that the engine was refitted with a Bowman exchanger, without up-grading the water pump.  All the same, when you next have a look, remember Sod's Second Law of Engineering :

If it is running smoothly and performing as you want it to, don't bugger about with it!    

[Smoggy]

1 hour ago, Vaughan said:

If it is running smoothly and performing as you want it to, don't bugger about with it!    

+1 on that theory.

[PaulN]

Thank you all you experts, much appreciated. I think I will change it just before de-winterising in the spring as it's 2½ years old and we spend about 16 to 18 weeks a year on the boat.

It is the original pump, the engine has only done 2,600 hours and externally at least, looks like new.

According to Beta the impeller is a 6 bladed Johnson ref: 09-810B-01. They had full details of where it was supplied to (Swancraft) and had a picture of my engine on the test bed before it was painted, even though it is 14 years old.

Griff, Meantime, Marge&Parge, Vaughan all great advice (and yes Vaughan you were the expert I had in mind). Thank you all again.

Paul