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Posted: Mon Sep 07, 2009 7:39pm

Post Subject: cost of new engine

Hi Tony, I'd like to get some idea of the cost to replace a wide beam narrowboat engine. I know there is the question of balancing the sytem i.e. engine/prop shaft/propeller etc. with the actual boat itself - so any ball park figures? I'd be having to navigate rivers (the Trent, for one), and lets say an Isuzu 55hp - although I'm open to suggestions. The more I get into this question the more I realise how much there is to ponder - any pointers for me? The defunct engine was a Perkins three cylinder (HP unknown). Thanks.


Posted: Tue Sep 08, 2009 8:37am

Post Subject: cost of new engine

Dear Tim, unless your boat has been built in a very amateurish way I doubt you need worry about the propshaft except in so far as altering it to suit a different length of engine. You will however have to consider the propeller size against the engine torque curve and gearbox reduction. The maximum diameter of the propeller is fixed by the need for two inches clearance between the blade tip and any fixed part of the hull. You need to establish this yours elf on your boat, but on modern hulls it is often about 16 inches. The pitch (twist on the blades) can be altered to suit. Now, I think your gearbox on the Perkins may well be OK for continued use but you need to identify it and then check its maximum torque/speed is suitable for the new engine. If this is OK and your adaptor plate fits the new engine you could save perhaps £1000+. Now why you think I the cost of any engine better than the mariniser/ agent is beyond me. You need to ask them. Once you have decided on the actual engine you can get the torque graph and use those in the Prop Calculator you can download from the Castle Marine (Wales) website to see how close a match your prop will be. If its a long way out go to an inland specialist for the cost of a new prop - say Crowthers. Even once you have sorted that lot out you need to ensure the shaft can be aligned to the new engine (its gearbox coupling may be in a different place relative to the engine feet). If it can't you may need engine bed surgery or fitting something like an Aquadrive. You ask for a ball park figure but without knowing all the details this is all but impossible, I will say allow up to £10,000 to include labour. If you are not capable of doing it yourself and do not have access to a trusted engineering setup may I suggest that you phone River Canal Rescue Ltd. and ask their Canal Contracting subsidiary to give yo a quote for the whole job. Tony Brooks

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