Impeller VP TAMD41P

Jamie Dundee

Jamie Dundee

Well-Known Member
Joined
24 Jul 2019
Messages
1,544
Visit site
As part of preparing my new (to me) boat for the season I cleaned out the raw water strainer and changed the impeller. The engine was pumping water perfectly before the change, I just wanted to start the season with a new clean system. The engine now will not pump water, even with a hose directly into the raw water strainer. I've tried two different new impellers, same problem. Is it possible to get an airlock in the raw water system between the strainer and pump?
 
I have kad32 but that's the same pump an d strainer arrangement .
I assume your boat is sterndrive so no sea cock .
My usual practice is to top up the strainer with water and put the sealing disk on and screw the top on promptly so as to minimise any air pocket . Then start the engine and it has never failed to work.
 
Are you certain you have the correct impellors both in diameter and length. Do they look the exactly the same side by side. ?
Feel sure there are a minor few variations in impellor sizes
Is the facing plate air tight on pump body ie does it need a paper gasket or rubber ring to seal , smear of jointing compound to make sure.
Is the plate worn ?' It should work even with considerable wear.
You can reverse the plate with lettering on the inside .
Have you tried using hose pipe mains water pressure to force out any air in system.
When starting up engine after impellor change, hold a finger or two on the brass plate on front of pump, should be stone cold, Will get warm very quickly if no water present .
 
Last edited:
The boat is shaft drive but all seacocks are open and a hose directly to the strainer doesn't work. One impeller is original Volvo, the other is an Orbitrade pattern part, both identical to the old impeller. I've fitted a new sealing ring on the pump plate and smeared the impellers and seal with the supplied lubricant, all a good airtight fit. I wondered about running the hose into the strainer with the pump cover off to allow any airlock to work out of the system? All was working fine until I messed with it, wish I'd left it alone now :confused:
 
I am not sure whether the pump works properly when the sealing disc and screw cover are not in place .
 
Jamie Dundee said:
As part of preparing my new (to me) boat for the season I cleaned out the raw water strainer and changed the impeller. The engine was pumping water perfectly before the change, I just wanted to start the season with a new clean system. The engine now will not pump water, even with a hose directly into the raw water strainer. I've tried two different new impellers, same problem. Is it possible to get an airlock in the raw water system between the strainer and pump?
Click to expand...
It’ is air locked by the exhaust gas back pressure , you need to vent the output hose from the pump after the impeller while engine is running .
 
volvopaul said:
It’ is air locked by the exhaust gas back pressure , you need to vent the output hose from the pump after the impeller while engine is running .
Click to expand...
Great, thanks. Presumably changing the impeller whilst messing with the strainer is a bad idea?
 
Popped the outlet hose off the pump with a hose in the strainer, started the engine.....success :) Refitted the outlet hose and loads of water through the exhaust.

Thanks all and Volvopaul for the input and solution.
 
Still having a problem with this. Popping the outlet hose off the pump allows water to flow and it pumps strongly. Turning the engine off then on again recreates the problem, the pump doesn’t even clear the water remaining in the strainer unless the hose is removed again. My mechanic is baffled as there is no apparent reason for this behaviour, the impellers are new and the system was working perfectly before the impeller change, nothing other than the impeller has been touched and the strainer can’t be the problem.

Baffled :unsure:

Just to add, when the engine is started it pumps out any water still in the system, ie exhaust, heat exchanger etc, downstream of the pump, but with our drawing fresh water from the strainer. It would seem that the problem is between the strainer and pump but nothing has been changed there since the system was working.
 
Last edited:
Jamie Dundee said:
Still having a problem with this. Popping the outlet hose off the pump allows water to flow and it pumps strongly. Turning the engine off then on again recreates the problem, the pump doesn’t even clear the water remaining in the strainer unless the hose is removed again. My mechanic is baffled as there is no apparent reason for this behaviour, the impellers are new and the system was working perfectly before the impeller change, nothing other than the impeller has been touched and the strainer can’t be the problem.

Baffled :unsure:

Just to add, when the engine is started it pumps out any water still in the system, ie exhaust, heat exchanger etc, downstream of the pump, but with our drawing fresh water from the strainer. It would seem that the problem is between the strainer and pump but nothing has been changed there since the system was working.
Click to expand...
You could have a melted exhaust not allowing the gas to escape
 
volvopaul said:
You could have a melted exhaust not allowing the gas to escape
Click to expand...
Surely then it wouldn’t work at all? Once water is flowing all is ok with plenty of water being pumped out of the exhaust. The engine has never been run for more than a few seconds without flow and exhaust gasses continue to pass through the exhaust when water flow stops.
 
edit mis- understood. Have you tried fitting a new length of hose direct from the pump inlet into a big bucket/container of water with a hose pipe feeding water into a big bucket/container - by passing the strainer , gearbox cooler and associated pipes and bits? If you run the engine at idle the hose pipe will keep up ok, Just make sure the bucket/container is pretty full before you start the engine.

Is the strainer plastic? It may be cracked somewhere so sucking air rather than water. Check out the state of the seal in the top of the strainer - is it there? The hose from the pump to the strainer could be porous as well. How high is the top of the strainer relative to the engine? Check out the hose from the sea cock to the strainer too. Hoses can be porous but not actually leak water when water is flowing. Old hoses go brittle and don't always seal with jubilee clips around them. Check out the gearbox cooler (bypass it temporarily at idle)

Dont worry about it all working before - all that has happened is that something has failed that would have failed anyway. Better to know now than 1/2 a mile out to sea. There is a reason, it will be dead obvious when you find it. When you find it do the same quality repair on the other engine.
 
Last edited:
kashurst said:
edit mis- understood. Have you tried fitting a new length of hose direct from the pump inlet into a big bucket/container of water with a hose pipe feeding water into a big bucket/container - by passing the strainer , gearbox cooler and associated pipes and bits? If you run the engine at idle the hose pipe will keep up ok, Just make sure the bucket/container is pretty full before you start the engine.

Is the strainer plastic? It may be cracked somewhere so sucking air rather than water. Check out the state of the seal in the top of the strainer - is it there? The hose from the pump to the strainer could be porous as well. How high is the top of the strainer relative to the engine? Check out the hose from the sea cock to the strainer too. Hoses can be porous but not actually leak water when water is flowing. Old hoses go brittle and don't always seal with jubilee clips around them. Check out the gearbox cooler (bypass it temporarily at idle)

Dont worry about it all working before - all that has happened is that something has failed that would have failed anyway. Better to know now than 1/2 a mile out to sea. There is a reason, it will be dead obvious when you find it. When you find it do the same quality repair on the other engine.
Click to expand...
I think bypassing the gearbox will be the next step. I don’t think the strainer is the problem as I’m using a hose into the open strainer to feed water. It’s as if there is a recurring airlock between pump and strainer, once water is in the pump all is ok but every time the engine is started I have to remove the exit hose from the pump to allow it to reprime.

My edit; although the pump doesn’t pull water into the system on start up it expels all water already in the exhaust, heat exchanger etc. So it appears to be pumping out but not drawing water in. Once the pump is reprimed it works perfectly.
 
I think you have a small air leak somewhere between the engine pump and the sea cock. It could be anywhere. It might be a weird plastic pipe failure or just a loose fixing. Assume nothing, take your time and be methodical. Do the pump with a new bit of hose into a bucket test a few times over a few days until you are sure the engine starts and sucks up water without hesitation every time. Then work your way back through all the connections and parts. It will be quicker and you will know thereafter every part of that system is good for the future. Use a heat gun to soften the plastic/rubber pipes up where they join onto fittings - it makes life much easier. If the pipes have been on a long time they can be a bugger to get off so get them quite hot and supple before tugging and swearing. If you are tackling this in the next few weeks you will be glad of the warmth. You can test out the gearbox cooler again by putting your new bit of hose onto the inlet side and again into a bucket filled with water etc. Fingers crossed its either something loose or just old, brittle plastic bits.
 
kashurst said:
edit mis- understood. Have you tried fitting a new length of hose direct from the pump inlet into a big bucket/container of water with a hose pipe feeding water into a big bucket/container - by passing the strainer , gearbox cooler and associated pipes and bits? If you run the engine at idle the hose pipe will keep up ok, Just make sure the bucket/container is pretty full before you start the engine.

Is the strainer plastic? It may be cracked somewhere so sucking air rather than water. Check out the state of the seal in the top of the strainer - is it there? The hose from the pump to the strainer could be porous as well. How high is the top of the strainer relative to the engine? Check out the hose from the sea cock to the strainer too. Hoses can be porous but not actually leak water when water is flowing. Old hoses go brittle and don't always seal with jubilee clips around them. Check out the gearbox cooler (bypass it temporarily at idle)

Dont worry about it all working before - all that has happened is that something has failed that would have failed anyway. Better to know now than 1/2 a mile out to sea. There is a reason, it will be dead obvious when you find it. When you find it do the same quality repair on the other engine.
Click to expand...

Are we taking shaft drive or Outdrive version here ?
If shaft drive what gearbox ?
 
just another thought sometimes there is an anti-siphon valve either as part of the strainer or a separate part. Usually they are after the pump but you never know with old boats what previous owners may have done.
 
Last edited:
kashurst said:
just another thought sometimes there is an anti-siphon valve either as part of the strainer or a separate part. Usually they are after the pump but you never know with old boats what previous owners may have done.
Click to expand...
Plenty there to be getting on with. Think I’ll start by bypassing the gearbox, I’m convinced the problem is between the pump and strainer. No problem with the bilge pump as the boat is currently on the hard.
 
On my tmd41's often when the raw system has been run dry one will suck up no problem but the other wont lift anything till primed, sometimes I have to fill strainer (above pump level) and loosed pump cover plate and let some water trickle through before it will do anything, I rebuilt the pump and no different, I swapped the pumps over to check for plumbing differences and the same pump still gave problems, once primed it will be fine all summer till drained again.
I machined the back of the pump to allow a jabsco wear plate fit in the back and that made no odds either.
 
You must log in or register to reply here.

Share this page

Top