Raw water pump pulley issues

[MarkCC]

Hey 

 

I'm currently "playing" around with a new project boat and am having an issue with some over heating. 

 

The boat has a raw water cooling exhaust type system, with a jabsco water pump powered by a pulley /belt. 

 

The engine is overheating and it looks like the belt is too slack - but i can't work out how to tighten it. Dumb I know- the 'wheel' at the pump is attached to the pump and so no real that end. The other end has 3 bolts going into it but doesn't seem to be able to 'move' to allow any slackening or tightening. 

I'm sure its something obvious but its driving me blind. 

 

Its a mitsubitshi l 3e engine if that helps any. 

[MtB]

The energy required to pump raw water through the heat exchanger and into the (presumably) wet exhaust is trivial so the belt doesn't need to be particularly tight. 

 

How much water can you see coming from the exhaust? If there is plenty then I'd be dismantling the HE looking for contamination. If very little, I'd be inspecting the impeller in the RW pump. The vanes have a tendency to break off and if you find this, then I suggest you are in for some fun finding the broken-off vanes! If the impeller is good, then its back to looking for blockages, starting in the HE. 

 

 

Edited December 30, 2021 by MtB
Add a bit.

[Tony Brooks]

Is it a foot mounted pump, if so the bracket it is bolted to may have slots in it for the securing bolts so it can be moved about, otherwise you could pack under the foot, thin plywood would do.

 

If it is mounted directly onto the engine then the raw water pump belts will drive enough when slack.  Not knowing f it is direct raw water cooled or heat exchanger it is difficult to know what to suggest you do next. I assume that you have checked the pump impeller and the case plus end plate(s) for wear. The it is check the ends of nay heat exchanger core for blocking, hose/pipe elbows for blockage, the while system between raw water inlet and pump for air leaks, the exhaust mixing elbow for excess scale and finally the exhaust hose for  delamination or blockage. Exhaust back pressure will reduce the pump output or stop it completely although the pump is turning.

 

[ditchcrawler]

The other belt is starting to look a bit ragged 

[MarkCC]

OK

 

I replaced the impeller today as I thought that might be the issue and it was truly knackered. However the engine very quickly got up to 90+c and I decided best to stop. 

[Tony Brooks]

Also check the pump shaft for "lift", the bodies can wear allowing the pump  to suck air between shaft and body, depending upon type of pump.

Just now, MarkCC said:

OK

 

I replaced the impeller today as I thought that might be the issue and it was truly knackered. However the engine very quickly got up to 90+c and I decided best to stop. 

 

Can you check that with an infra red thermometer on the thermostat housing because that might not be a true reading. The sender could be faulty or an idiot may have mixed US and European gauge and sender. that could make it read about twice or half what it should.

[Momac]

https://www.mhi.com/group/mvde/products/mvl3e-engine.html

I thought the above might help but I suspect not.

 

If the impeller was  shot - were bits of impeller missing?  and if so is the heat exchanger downstream from the pump?

Edited December 30, 2021 by MartynG

[MarkCC]

Cheers chaps 

 

Its a jabsco 4900-200   bolted on to the engine 

[MarkCC]

The raw water comes in goes around and up to the metal cylinder box thingy (not sure what its called) comes out then down into the bottom of the pump then up and through the housing where it joins the air exhaust - down to a 'mud box' then out ... 

 

If that makes sense (sorry still learning the jingo for wet exhausts) 

[Alan de Enfield]

42 minutes ago, MarkCC said:

OK

 

I replaced the impeller today as I thought that might be the issue and it was truly knackered. However the engine very quickly got up to 90+c and I decided best to stop. 

 

You did check the impeller rotation and pre-shape the vanes before fitting into the pump-housing didn't you ?

 

Put a jubilee clip (or cable tie) over the vanes and squash them into shape, this allows you to slide them half-way into the housing, then slide off the clip / tie and push it in the rest of the way.

 

You can see the amount of bend in the impeller vanes - put them in bent the wrong way and they shear off you get blocked tubes and you get no water flow.

 

 

 

 

What happens when you get an impeller like this ?

 

 

 

Edited December 30, 2021 by Alan de Enfield

[MarkCC]

I took a picture of how it was arranged before and put it in the same way. 

 

I stopped worrying about the belt tension following some advice above. 

 

I've cleared the pipes and I think there might have been a blockage caused by the knackered impeller. Been running for 15mins now happily sitting at about 70degrees. 

 

So my current thinking is broken impeller plus debris from it stuffed it up. 

 

Thanks everyone for the help, assistance and reassurance. We take her for a cruise tomorrow and see how that issue goes. 

 

 

 

 

And just whilst I have the thread going anyone have any ideas why the boat will only go one speed? 

 

It will rev up whilst in neutral, but as soon as I put it in to either gear it does not rev at all. Its a hydraulic gear system (another new thing for me) I've topped up the hydraulic oil etc 

[Bee]

Presumably it has a 'wet' exhaust so the water comes out of the exhaust? Does it come out in a miserable trickle or a decent splash? I can't see a filter so clogging might be an issue - duckweed is a sod and so are leaves but keeping it clear of stuff might be an ongoing problem.  I'm afraid hydraulic drive is a bit of a mystery to me but it should rev, 

Edited December 30, 2021 by Bee

[MarkCC]

It was a trickle or nothing at all, now looks healthier splash now  🙂

 

Heres the impeller image 

[Bee]

Hm, I've got some just like that, They last about a year or two then all the fins break off and othing works.

[Tony Brooks]

37 minutes ago, MarkCC said:

It will rev up whilst in neutral, but as soon as I put it in to either gear it does not rev at all. Its a hydraulic gear system (another new thing for me) I've topped up the hydraulic oil etc 

 

Is it a hydraulic GEARBOX or a Hydraulic drive system with a hydraulic pump and motor? What did you top up, a gearbox or a  largish steel "box".

 

I would initially expect a badly fouled prop that is preventing the engine revving up when the prop is connected to the engine. It could be a stupidly over-tight  stern gland or a seized shaft - especially if it is mild steel and has been standing for years.

 

It might be a lack of fuel that only allow enough for revving under no load so the first thing to have a look at is what is in the filters and any water traps and report back.

Edited December 30, 2021 by Tony Brooks

[MarkCC]

Thanks Tony 

 

I knew I would be caught out with needing more info. 

 

Not an upto date picture as I have put in a bilge pump since this picture was taken .. 😉

 

The metal square box. With the qx 32 (?) oil I found on board. 

 

The gears make a hissing hydraulic noise when engaged so assumed the gears but there are various pipes going hither and tither so maybe the drive too. 

 

 

 

But this boat seems a wonder of mysteries and oddities. 

 

[Momac]

43 minutes ago, MarkCC said:

It was a trickle or nothing at all, now looks healthier splash now  🙂

 

Heres the impeller image 

Hopefully you have recovered all of the missing parts.

[Tony Brooks]

That is a hydraulic DRIVE system, otherwise known as a hydrostatic drive. What you can hear is the noise from the hydraulic motor that is hidden below the  wooden cross member. It will normally whirr when ahead or astern is selected but no more than that. The hissing could well be the Pressure Relief Valve operating and that suggests a fouled prop, seized shaft, seized of jammed motor.

 

The PRV will early operate on a properly set up system except for a split second as a "gear" is selected or if the prop, shaft, or motor jambs. That is unless and idiot has been tampering with it's setting but forget that for now. Try turning the shaft by hand.

Edited December 30, 2021 by Tony Brooks

[Momac]

49 minutes ago, Bee said:

Hm, I've got some just like that, They last about a year or two then all the fins break off and nothing works.

 

I inspect the impellers  annually and more often than not find some splitting has  started at the root of some vanes . At that point a new impeller is required .

 

[Ex Brummie]

Replacement of the impeller is an annual service requirement. Poor performance is not so crucial on canals, but failure can be disastrous on lumpy water or strong rivers.

I can't see whether your overheating has been cured, but the belt to your engine water pump looks pretty poor. Is that pump working?

[David Mack]

4 hours ago, ditchcrawler said:

The other belt is starting to look a bit ragged 

The V surfaces on the pulleys look rusty too, suggesting this engine hasn't run for a while.

[MtB]

3 hours ago, MarkCC said:

But this boat seems a wonder of mysteries and oddities. 

 

 

They are all like that 

 

Tony may well correct me but AIUI with hydraulic drives, the engine is set to run at a constant speed and the prop/boat speed is adjusted by the valves connected to the user controls.

[Tony Brooks]

11 hours ago, MtB said:

 

 

They are all like that 

 

Tony may well correct me but AIUI with hydraulic drives, the engine is set to run at a constant speed and the prop/boat speed is adjusted by the valves connected to the user controls.

 

I agree with your first paragraph and because of that I am sure  some boats are like that, especially if the builder had power hydraulics experience, but all those I have seen have not been like that. They used simple fixed displacement pumps and motors and speed control was all done by engine revs. The OP's image shows what looks very much like a fixed displacement pump to me except It seems to have a pair of extra pipes. No idea why though.

 

Don't let the Beta Propgens make you think they are hydraulic. They run at a constant engine speed and alter the prop speed by in effect slipping the gearbox clutches (it's more complicated than that and involves driving through fluid friction in the clutches if I understand it correctly and that is a big IF.

[Alan de Enfield]

22 minutes ago, Tony Brooks said:

 

I agree with your first paragraph and because of that I am sure  some boats are like that, especially if the builder had power hydraulics experience, but all those I have seen have not been like that. They used simple fixed displacement pumps and motors and speed control was all done by engine revs. The OP's image shows what looks very much like a fixed displacement pump to me except It seems to have a pair of extra pipes. No idea why though.

 

Don't let the Beta Propgens make you think they are hydraulic. They run at a constant engine speed and alter the prop speed by in effect slipping the gearbox clutches (it's more complicated than that and involves driving through fluid friction in the clutches if I understand it correctly and that is a big IF.

 

 

Similar to Diggers, Dumpers, Tractors, Ride-On-Mowers etc. Simply put the engine throttle on 'full' (to 'the stop') and the actual forward speed is controlled by varying the hydraulic flow with the foot / hand 'throttle'.

[MarkCC]

A couple of hours cruising and she topped out at 85c- so I think the main issue with the water pump etc is sorted atleast for now. 

 

 

Following on I think the prop is having issues as the boat struggles under load (loads of smoke - enough to cause second looks etc - adding the fact she only goes 1 speed im sure to be terrorising other boats) 

 

So, have a look at the prop because that might explain a few issues. 

Firstly it does turn by hand but is very stubborn. 

Into the weed hatch..  its the bolted down variety but get in and I am able to remove the foot type piece. Haha I think now to look at the propeller ...nope there's another piece of metal blocking me getting to propeller... 

It does have a bit of a gap as I poured some water in and it drained away.  

Answers on a postcard  

 

Thanks again for your knowledge and wisdom.