Tony Brooks Posted May 2, 2019 Report Share Posted May 2, 2019 (edited) 14 minutes ago, Stephen Jeavons said: Back to the topic (sort of). What is the maximum RPM anyone has had to use on various rivers to maintain a reasonable canal-like speed? I realise prop-pitch has a bearing on this. Just curious. When turning to face the tide and motoring up to and into West Stockwith lock about 2500 rpm and the flat out at about 2800 to turn into the lock (I hit the wall!). Going downstream with the Thames close to full flood canal speed would be more or less tick over, stemming the current more than 2000 rpm. My boat is probably over propped for maximum power so it can not reach the 3600 maximum RPM. Normally when on rivers I have no thought about sticking to canal-like speed, I just watch the wash. Edited May 2, 2019 by Tony Brooks Link to comment Share on other sites More sharing options...
Stephen Jeavons Posted May 2, 2019 Report Share Posted May 2, 2019 Thanks Tony, Would you say that the skin tank conducts heat away faster when stemming the current or do you think the river's cooling effect is the same on the skin tank regardless of whether it is flowing fast or not? Link to comment Share on other sites More sharing options...
Tony Brooks Posted May 2, 2019 Report Share Posted May 2, 2019 (edited) I think as long as you are in open water the speed you are runing through the water makes no difference to the cooling. What MIGHT is if the skin tank side of the swim was very close to the bank with the base plate in mud so it is difficult for convection in the canal water to carry heat away but even then you will need to heat a lot of canal water before cooling becomes an issue. All supposing the skin tank is large enough. Basically if you overheat on rivers the most likely cause is an undersized skin tank. Edited May 2, 2019 by Tony Brooks Link to comment Share on other sites More sharing options...
GUMPY Posted May 2, 2019 Report Share Posted May 2, 2019 1 hour ago, Stephen Jeavons said: Back to the topic (sort of). What is the maximum RPM anyone has had to use on various rivers to maintain a reasonable canal-like speed? I realise prop-pitch has a bearing on this. Just curious. 1550 rpm pushes Loddon along easily at 6mph in deep water. Engine will pull 2000 which is about 7.5mph, never yet not had enough power Most canal cruising is at about 1100rpm/3-4mph if that. 50hp is nice to have in a 60ft NB Link to comment Share on other sites More sharing options...
Tony Brooks Posted May 2, 2019 Report Share Posted May 2, 2019 1 hour ago, Loddon said: 1550 rpm pushes Loddon along easily at 6mph in deep water. Engine will pull 2000 which is about 7.5mph, never yet not had enough power Most canal cruising is at about 1100rpm/3-4mph if that. 50hp is nice to have in a 60ft NB Don't know how I could possibly manage with about 30hp on 54 ft. Link to comment Share on other sites More sharing options...
Alan de Enfield Posted May 2, 2019 Report Share Posted May 2, 2019 1 minute ago, Tony Brooks said: Don't know how I could possibly manage with about 30hp on 54 ft. I struggle along with 2x 140hp on a 36 footer. Did previously have 2x 200hp on a 31 footer. Link to comment Share on other sites More sharing options...
bigcol Posted May 2, 2019 Author Report Share Posted May 2, 2019 Okay. Speaking to the current owner, he him self built hi skin tank it measures 6ft x 1 ft by 2 inches thick. he welded the inside channels direct to the hull and put a lot of channel so the water is pumped arround a lot. after he welded the channels he welded the top on. this was done in the water!!! hes done 400 hrs on the Thames, never had a problem! what you on the forum quoted as square feet, beta,Martin Kiedan all agree with. i must admit Jambo Rafiki had a keel tank, and that had a 50hp, and that tant was no longer than 4ft approx? col Link to comment Share on other sites More sharing options...
GUMPY Posted May 2, 2019 Report Share Posted May 2, 2019 37 minutes ago, Alan de Enfield said: I struggle along with 2x 140hp on a 36 footer. Did previously have 2x 200hp on a 31 footer. With that you can turn in your own length. Link to comment Share on other sites More sharing options...
Alan de Enfield Posted May 2, 2019 Report Share Posted May 2, 2019 2 minutes ago, bigcol said: Okay. Speaking to the current owner, he him self built hi skin tank it measures 6ft x 1 ft by 2 inches thick. he welded the inside channels direct to the hull and put a lot of channel so the water is pumped arround a lot. after he welded the channels he welded the top on. this was done in the water!!! hes done 400 hrs on the Thames, never had a problem! what you on the forum quoted as square feet, beta,Martin Kiedan all agree with. i must admit Jambo Rafiki had a keel tank, and that had a 50hp, and that tant was no longer than 4ft approx? col 6 square feet (6 foot x 1 foot) is fine for a 24hp engine, or a bigger engine that is only producing up to 24hp. I have 2x 140hp engines but they are only producing 27hp when cruising at 5 knots at 1500rpm. For a 90hp engine you need about 25 square feet of cooling - if you are like likely to need full power. It will work with 6 square feet but the slightest increase of power to go against the tide, or battle the River as it comes into flood etc etc is the time it will boil-up, which will result in you 'losing the engine' at the time you probably need it the most. What size engine did it have in previously ? 4 minutes ago, Loddon said: With that you can turn in your own length. Easy when the props are 12 feet apart, even easier on the Cat where they are 21 feet apart. Link to comment Share on other sites More sharing options...
WotEver Posted May 2, 2019 Report Share Posted May 2, 2019 29 minutes ago, Alan de Enfield said: even easier on the Cat where they are 21 feet apart. Can you put one in fwd and one in reverse and just spin? The weirdest thing I ever experienced on a passenger jet was when we reversed up a taxiway to get to our gate. I didn’t even realise they could do that. Link to comment Share on other sites More sharing options...
Alan de Enfield Posted May 2, 2019 Report Share Posted May 2, 2019 10 minutes ago, WotEver said: Can you put one in fwd and one in reverse and just spin? The weirdest thing I ever experienced on a passenger jet was when we reversed up a taxiway to get to our gate. I didn’t even realise they could do that. Yup - that's the normal way of turning. I only use the 'wheel' at cruising speed. Link to comment Share on other sites More sharing options...
blackrose Posted May 2, 2019 Report Share Posted May 2, 2019 (edited) On 30/04/2019 at 13:19, David Mack said: Blackrose had a second skin tank welded in while the boat was in the water. There is a thread about it on here somewhere. Yes I had enough space on the inside of the swim to put a second skin tank in while the boat was in the water, but looks like Col needs his boat lifting out so tanks can be fitted on the outside. Edit: sounds like he's considering raw water cooling now Edited May 2, 2019 by blackrose Link to comment Share on other sites More sharing options...
tree monkey Posted May 2, 2019 Report Share Posted May 2, 2019 4 hours ago, Tony Brooks said: I think as long as you are in open water the speed you are runing through the water makes no difference to the cooling. What MIGHT is if the skin tank side of the swim was very close to the bank with the base plate in mud so it is difficult for convection in the canal water to carry heat away but even then you will need to heat a lot of canal water before cooling becomes an issue. All supposing the skin tank is large enough. Basically if you overheat on rivers the most likely cause is an undersized skin tank. This is likely to sound daft and be obvious as to why it's impossible to those who understand these things but... Would it be possible to parallel skin tank and raw water cooling, even just use the skin tank when canal pottering and switch in the raw water as and when? Link to comment Share on other sites More sharing options...
blackrose Posted May 2, 2019 Report Share Posted May 2, 2019 2 hours ago, Alan de Enfield said: 6 square feet (6 foot x 1 foot) is fine for a 24hp engine, or a bigger engine that is only producing up to 24hp. I have 2x 140hp engines but they are only producing 27hp when cruising at 5 knots at 1500rpm. For a 90hp engine you need about 25 square feet of cooling - if you are like likely to need full power. It will work with 6 square feet but the slightest increase of power to go against the tide, or battle the River as it comes into flood etc etc is the time it will boil-up, which will result in you 'losing the engine' at the time you probably need it the most. What size engine did it have in previously ? And also do you have any idea whether the previous owner was actually in any situations where they needed to use a substantial part or full power of the engine? If they weren't then that may explain why they never realised it was undercooled. Many owners don't realise because they never venture from canals or have only gone downstream on rivers. Link to comment Share on other sites More sharing options...
alan_fincher Posted May 2, 2019 Report Share Posted May 2, 2019 3 hours ago, Tony Brooks said: Don't know how I could possibly manage with about 30hp on 54 ft. Or me with 22HP for 72 feet........ Link to comment Share on other sites More sharing options...
WotEver Posted May 2, 2019 Report Share Posted May 2, 2019 55 minutes ago, blackrose said: Many owners don't realise because they never venture from canals or have only gone downstream on rivers. If he’s spent 400 hours on the Thames I guess some of that must have been against the flow, surely? Link to comment Share on other sites More sharing options...
GUMPY Posted May 2, 2019 Report Share Posted May 2, 2019 40 minutes ago, alan_fincher said: Or me with 22HP for 72 feet........ But your 22hp are old 22hp With bigger torques than modern engines. Link to comment Share on other sites More sharing options...
Iain_S Posted May 2, 2019 Report Share Posted May 2, 2019 4 hours ago, tree monkey said: This is likely to sound daft and be obvious as to why it's impossible to those who understand these things but... Would it be possible to parallel skin tank and raw water cooling, even just use the skin tank when canal pottering and switch in the raw water as and when? It would certainly be possible. If the heat exchanger had a core in it, as per indirect raw water cooling, the raw water could be supplied, if required, by a switchable (electric probably easiest) pump. When we had overheating problems in Copperkins, the temporary solution was a hose connected to a tap in the rear cabin basin with the nozzle set to provide a fine spray over the inside of the skin tank. Worked a treat, with very little water ending up in the bilge: it all evaporated. (I suppose if we'd been scientifically minded, we could have measured the flow rate, and worked out how much heat was being removed.) We did think of modifying this, using a bilge pump feeding water to a spraybar on top of the skin tank, but the actual problem was traced to a lack of baffles in the skin tank, and when that was rectified, the cooling system worked properly. Link to comment Share on other sites More sharing options...
TheBiscuits Posted May 3, 2019 Report Share Posted May 3, 2019 8 hours ago, Loddon said: But your 22hp are old 22hp With bigger torques than modern engines. Now yer torqueing I think they had bigger horsepowers in the olden days, or maybe bigger propellers!. . Link to comment Share on other sites More sharing options...
blackrose Posted May 3, 2019 Report Share Posted May 3, 2019 (edited) 9 hours ago, WotEver said: If he’s spent 400 hours on the Thames I guess some of that must have been against the flow, surely? Yes that's true, but in summer the Thames can be very placid, with reaches like pools without much flow at all. We don't know what those 400 hours were spent doing. The previous owner might have just been running the engine moored up for a lot of it for all we know. What we do know is that the keel cooling described is insufficient for a 90hp engine. Edited May 3, 2019 by blackrose Link to comment Share on other sites More sharing options...
bigcol Posted May 3, 2019 Author Report Share Posted May 3, 2019 Okay this is where we at. we have decided to convert the engine to Raw water cooled had BETA give me a quote for the whole kit needed Please see the list below: Tube stack 209-02846 £400.00 End cap In/out 209-03326 £75.00 End cap return 209-03327 £75.00 2x H/E o-ring 209-00814 £3.73 each Raw water pump 207-01178/01 £266.00 Coolant hose kit £100.00 Water injection bend 202-02458 £41.48 Exhaust 2” gasket 212-09070 £5.00 Anode 209-61840 £9.00 This with discount of 35% plus 20% vat plus labour approx 2 hours labour. the engine turns out to be a 2005, it’s 500 hrs on the clock but have seen video of it running as do beta. the engine has rarely been used in all this time, but ran up at least once a year. engine arrives next week when it will be converted. have to source a 24v alternator so thanks again for the keel tank posts, hope it helps other folks who does not know exactly has much keel tank to have. so soon the boat will have a engine col Davy Way, Waterwells, Quedgeley, Gloucester GB -GL2 2AD Tel: +44 (0)1452 723492 Fax: +44 (0)1452 883742 Registration No. 2114058 VAT No. GB 466 8455 03 email: waynenota@betamarine.co.uk website: www.betamarine.co.uk Link to comment Share on other sites More sharing options...
Boater Sam Posted May 3, 2019 Report Share Posted May 3, 2019 Nice list of parts but what about getting a mud box made and installed? Have you budgeted for that? Link to comment Share on other sites More sharing options...
bigcol Posted May 3, 2019 Author Report Share Posted May 3, 2019 2 minutes ago, Boater Sam said: Nice list of parts but what about getting a mud box made and installed? Have you budgeted for that? Hi Sam Doing that now Link to comment Share on other sites More sharing options...
Phoenix_V Posted May 3, 2019 Report Share Posted May 3, 2019 8 minutes ago, Boater Sam said: Nice list of parts but what about getting a mud box made and installed? Have you budgeted for that? and the rest of the exhaust system, I presume you are going for water injected Link to comment Share on other sites More sharing options...
Alan de Enfield Posted May 3, 2019 Report Share Posted May 3, 2019 27 minutes ago, bigcol said: Raw water pump 207-01178/01 £266.00 That seems very reasonable - mine are £450 each (I have 2 of them) You don't get much change when you : Bring Out Another Thousand Link to comment Share on other sites More sharing options...
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