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Water Rail Out And About.


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1 minute ago, Vaughan said:

Sorry, but I don't get that? We are talking about an oil leak from the rocker shaft.

The later version of raw water pump with 10 vanes on the impeller rather than 12, was developed by myself and Peachments to avoid the back pressure caused by the small bore of the exhaust water injection bend. It was not possible to drill out the bend much larger so we had to experiment with the flow rate of the water pump. Early Nannis suffered from serious overheating until we found this balance, between the flow, and the back pressure.

Sorry I should have been clearer. I understand you are talking about an oil leak from the rocker shaft, which you stated affected the early Nanni 4190. I have a Nanni 4190 and whilst I don't currently have that problem, I am now aware it could be a future problem if it is a weak known stock fault / problem area.

However I do have a coolant, not raw water, pump that is showing significant signs of wear and over the Winter as preventative maintenance intend to change it. Those water pumps come in two variants. 11 or 12 I cannot remember bolt holes, or a slightly longer variant with 15 bolt holes which was fitted to the later Nanni 4190 engines. Since mine has 15 bolt holes it hopefully dates my engine as a later 4190, in which case it may not suffer the oil leak problem you helpfully described.

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  • 3 months later...
On 04/09/2022 at 11:17, Vaughan said:

Sorry, but I don't get that? We are talking about an oil leak from the rocker shaft.

The later version of raw water pump with 10 vanes on the impeller rather than 12, was developed by myself and Peachments to avoid the back pressure caused by the small bore of the exhaust water injection bend. It was not possible to drill out the bend much larger so we had to experiment with the flow rate of the water pump. Early Nannis suffered from serious overheating until we found this balance, between the flow, and the back pressure.

Vaughan - I'm interested in this insight as my engine doesn't like going over 2000rpm for very long (approx 10 minutes) before the temp starts rising and the temp alarm is triggered - not that it needs to very often apart from maybe when going through Yarmouth against the tide heading north. I've checked the tube rack in the heat exchanger and all seems good. My next check was going to be the exhaust elbow for some sort of restriction, and then the engines fresh water impeller that Meantime spoke about (though this would mean draining the engine coolant etc) but reading your post you have given me another option to think about......

I have a Nanni 4.190HE with a Jabsco ¾" (3270-271) raw water pump and it has a 12 blade impeller (see photo attached)- could I change the impeller for a 10 vane one and try that? or does the whole raw water pump need replacing to move to a 10 vane impeller?

Note: Karizma was built in 1994 so I'm assuming the engine is original and therefore of a similar vintage.

Cheers, 

IMG_9932.jpg

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On 04/09/2022 at 11:26, Meantime said:

However I do have a coolant, not raw water, pump that is showing significant signs of wear and over the Winter as preventative maintenance intend to change it. Those water pumps come in two variants. 11 or 12 I cannot remember bolt holes, or a slightly longer variant with 15 bolt holes which was fitted to the later Nanni 4190 engines.

Hi Meantime - I'd be very interested in how you get on with changing the fresh water impeller and wether it made a difference.

By the way - how did you identify it was showing significant signs of wear? did you strip it down or could you check it without stripping down?

Cheers,

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Hi Karizma,

We are going back a bit a bit now!  I joined Crown Blue Line in 1993 and their new boats all had the Nanni 4190 engine, which ran very well.  It was only when they changed to the 4220, with the same size raw water pump,  that we began to have trouble.

So we fitted a larger raw water pump and it was then that we started having the vanes stripping off the impellers.  We set up a test bench at Peachments and discovered it was caused by too much flow from the 12 blade impeller, causing a back pressure in the pipework.  So we fitted a 10 blade impeller and that cured it.  I think though, that this pump was larger than the one you have today on your 4190.

I suspect that the problem may lie with the tube stack in the heat exchanger.  It may look all right but it might be "furred up" and need putting in a bath of mild acid to get it clean.  There is also a more modern design of tube stack which gives a better flow of engine water, around the tubes.

I suggest the best thing is to talk to Peachments about it.  Ask for Andrew Peachment, tell him that you have spoken to me, give him my kind regards, and I know he will give you the best advice.

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5 hours ago, Vaughan said:

Hi Karizma,

We are going back a bit a bit now!  I joined Crown Blue Line in 1993 and their new boats all had the Nanni 4190 engine, which ran very well.  It was only when they changed to the 4220, with the same size raw water pump,  that we began to have trouble.

So we fitted a larger raw water pump and it was then that we started having the vanes stripping off the impellers.  We set up a test bench at Peachments and discovered it was caused by too much flow from the 12 blade impeller, causing a back pressure in the pipework.  So we fitted a 10 blade impeller and that cured it.  I think though, that this pump was larger than the one you have today on your 4190.

I suspect that the problem may lie with the tube stack in the heat exchanger.  It may look all right but it might be "furred up" and need putting in a bath of mild acid to get it clean.  There is also a more modern design of tube stack which gives a better flow of engine water, around the tubes.

I suggest the best thing is to talk to Peachments about it.  Ask for Andrew Peachment, tell him that you have spoken to me, give him my kind regards, and I know he will give you the best advice.

Thanks as always.

I'll take another look at the tube stack ....... once I've replaced the cutlass bearing (hopefully this weekend) you advised me on!

Cheers,

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Rydlyme is the descaler most of the sea goers use for cleaning raw water cooling systems, should be a bit kinder to the metals than some options.

Of course if you were to fit a bigger pump you could always use a restricted tee fitting and have some exit via a separate skin fitting instead of fitting a lower capacity impellor, would also act as an anti-siphon loop for the exhaust (not that you need it on the broads).

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  • 4 months later...

Well it's that time again, the next trip on water rail.

Thursday, departed Canterbury  early, 6.30 am and after a slow meander up to lowestoft, was not surprised when water rail wasn't at the yacht station, I used the opportunity to purchase a temporary  toll from the yacht station.

Then it was round to Robins,  where I found a hive of activity around water rail. Only essential fittings were being fitted, the remainder will be fitted after the varnish has been done.about 2pm we got her in the cradle and lifted her the few extra inches to be able to get the rudder shaft in place, the old rudder and shift weren't pretty to look at, at least 2^ were missing off the end of the tube.

Rudder fitted we took her round to the slip and launched checked the bilges for leaks (minimal) and checked the bilge pump was operating, after a few minutes it stopped, oh good we thought.

Then I took her round and locked in. Off to the yacht station Quay, and loaded up. Then it was time to set off (About 4.30pm ) headed downstream at a steady  pace, all too soon ran into the incoming tide.

I had decided to stop at bug caste if I arrived with less than an hour to sunset,  in the end it was exactly 1 hour before sunset, so I pressed on, only passing a patrol boat on breydon as I sailed in a beautiful  sunset.

It was just turning 8pm when I moored up at great Yarmouth. 

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As I was crossing breydon I had noticed that the bilge pump wasn't providing a good flow, and when I lifted an engine hatch I noticed the water was a bit high in the bilge, this was rather worrying, so I carried on to get tied up at great Yarmouth,  as soon as I had moored it was down in the bilge to clear the pump.

This turned out not to be as easy as first thought as the normal procedure is to remove the steps and kneel in the front cabin, uh oh, 2" of water there, a quick trip round the boat picking up stuff on the floor and putting it up, then laying on the floor to reach the bilge pump, this was a good 8" under water, but I got  the housing cleared, immediately the pump worked better. Now to phone Dave and appraise him to the  situation. 

Unfortunately he was on his houseboat on Oulton Broad,  and the power boat racing was on. So he couldn't leave straight away. He did get to me later bringing the bilge pump that would have been fitted (if the rudder hadn't  used up all the time. We got the bilge pumped dry, the failure of the automatic switch was due to it being wedged under a bulkhead, with this sorted we watched and waited while the bilge pump cycled, satisfied that the pump could handle the water coming in as a result of drying out, we all went our respective ways. Me to bed

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Rising early as I wanted to catch the flood up the bureau, I noticed the flow changed and cast off at 6.30am, destination  north,  thus followed a 4 1/2 hour cruise up to Wroxham, under the bridge (6'9") and mired up. Some shopping was called for, and Roy's provided - food hall toyshop and DIY store.

Then called into the chippy on the way back for battered sausage and chips.

After eating, I had a coffee, a quick catchup on the forum, and soon it was time to leave again. This time I headed back downriver, destination  Salhouse,  on arrival there I moved on the end of the line in a spot of shade, as even factor 50 sunscreen  has its  limits. 

Then it was time to catch up with those already there and new arrivals, all too soon it was time to eat and catch up with the forum.

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1 hour ago, grendel said:

Rising early as I wanted to catch the flood up the bureau, I noticed the flow changed and cast off at 6.30am, destination  north, 

Oh :default_icon_redface: I do hope that's not some form of euphemism but just a trip up the Bure you were planning :default_rofl:

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So woke up at the usual time (5am), slowly got up and pottered around  for a bit, brewed up a coffee, and then caught up on the forum posts. After that I cooked a couple of cheese and bacon turnovers, for my breakfast. While all this was going on I spotted the bilge pump stream was divided, so a partially blocked skin fitting.

This was a perfect opportunity to test the paddle board and clear the problem.

As is to be e pected, no sooner had I got myself in position, the bilge pump promptly started up, this helped me clear the debris, and pretty soon the flow was looking great.

That do e I took a turn down the line of boats and back on the paddle board just to give those attendees awake already a chance to photograph me.

At 10 we headed to Ranworth for the c in c back to salhouse. The rest of the day, chatting and relaxing. I have bread dough rising and have just been called for the quiz.

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So after packing up everything at the meet, it was time to decide where to head, Coltishall I thought, so I prepared for Wroxham bridge by dropping the mast, and redeployment the paddleboard on the starboard Deck. 

Had a good trip upriver Wroxham bridge, and after avoiding a boat that dropped the pilot off, went through the bridge where I  spotted Broad ambition moored up near the pub.

Waved at griff, and got purdy loo,ing when I called her name. Then it was off on a peaceful meander up to Coltishall, the common was rammed, so I carried on to the locks, which was empty apart from a sailing boat, currently moored up, going to have a spot of lunch h, then a chilled out afternoon, that may include some paddle boarding. 

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43 minutes ago, grendel said:

So after packing up everything at the meet, it was time to decide where to head, Coltishall I thought, so I prepared for Wroxham bridge by dropping the mast, and redeployment the paddleboard on the starboard Deck. 

Had a good trip upriver Wroxham bridge, and after avoiding a boat that dropped the pilot off, went through the bridge where I  spotted Broad ambition moored up near the pub.

Waved at griff, and got purdy loo,ing when I called her name. Then it was off on a peaceful meander up to Coltishall, the common was rammed, so I carried on to the locks, which was empty apart from a sailing boat, currently moored up, going to have a spot of lunch h, then a chilled out afternoon, that may include some paddle boarding. 

How wonderful,  I bet it is really lovely up there.    Any photos?

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