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Hire Boat Engine Lifetime


andyg

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So don't worry Griff, you have hardly run it in yet! Just look up the manual for the recommended oil change period, as I forget.

Beta recommend minor service every 250 x Hrs with a major service every 750 x Hrs.  The last service I did was a major one at 2'250 x Hrs so when we get to 2'500 x Hrs it'll be a minor one.  I have done every service on 'B.A's Beta and we now know each other quite well and are on first name terms

Griff

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I have no expertise at all in marine engineering but I can say how quiet and smooth the Richardsons Nannis are in comparison to the older engines. Not all the older boats have had a Nanni replacement and the difference is noticeable. From that perspective, if Herbert Woods policy is not to replace engines then they're doing their customers a disservice.

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With the older diesels, most owners with some mechanical experience can replace injectors and glow plugs, they can probably strip the fuel pump and replace O rings and seals, but with modern engines, you are probably only able to do service items, like oil and filters etc.

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We have an ex hire with a 50hp Nanni, engine was allegedly fitted to the boat in 2006 replacing an Isuzu so I was told.

The engine still runs and feels as though its brand spanking, under my care its had oil and filters once a year.  

Going back to what Viking mentioned about running an engine with no load.  It was interesting to read the tech specs for this engine are 3020rpm WOT no load and 2800rpm with load.  I think it said the optimum running range is 2240-2520 rpm.  

At 2520rpm i would be doing about 8-9knts with the tide. 

We might be able to criticise some folk for speeding but at least we cant acuse them of not looking after thier engines. 

 

 

 

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Much of the real fuel consumption will depend on prop matching, if the prop is too coarse, it will be labouring and full throttle will not be achievd unless you can find a broad with a slope on it lol.

Now for all scientists out there, if there is a flow on the Broad then there will actually be a slope lol The upstream side of the broad will be higher than the down stream side, otherwise there would be no flow.

There will also be a slight curve, caused by the curvature of the earth.

Don't get your laser levels out just yet, the differences are minor over our small Broads.

Richard

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Prop matching - proper black art is that one.  Jason S0S24:7 sorted us out on this one, recommending a 4 x blade 16" jobby. the result was spot on first time,  around 100rpm below max acheived, meaning we were slightly over-propped.

Since then the Beta has run-in / loosened up which gave us another 25rpm or so, what really did it though was the addition of ZX1 in the engine and g/box.   Now assuming the water is deep / wide enough i.e Breydon or out at sea, we can achieve max revs just,  so we are at the optimum.

Griff

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Griff I am impressed, and also with Jason, as sea water is slightly denser than fresh, your boat will be sitting higher, but the water you push against is denser, so to achieve maximum revs in salt water too, is fantastic.

On outboards, the standard props are designed for small light and fast run abouts, they are not designed for heavy slow displacement vessels, but at canal speed this rarely mattered, where it does matter is a the bottom of the Bure when fighting the last part of the ebb.

Having said that, once you achieve your theoretical maximum displacement speed then any speed greater than this will just create a bigger bow wave, which you then try to climb, but of course you can't as you can't plane, and don't have the extra power.

Props are really a compromise, for the best match, and best fuel economy, you probably need to start with your preferred cruising speed and prop accordingly. But as Griff says, a black art indeed.

Richard 

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Just what 'B.A's theoretical max displacement speed is - I'm not sure.  We could be well achieving it with the power train we have at present.  The Beta 50hp seemed the correct one to purchase at the time.  A couple of years later Beta started production of a 60hp unit of about same dimensions.  Had that been available at the time, we would have probably gone for it.  Not for extra top end speed but more pitch on the blades giving more thrust when undertaking berthing manoeuvres and the like.

I've often wondered what would happen if we could somehow install at 200hp unit in 'B.A' - would she plane?  If she did then she would probably violently skip from port to stbd and back again necessitating trim tabs and the like.  It's never going to happen of course, just me musing with the theories etc

Griff

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Now I think I have this right that hull speed in knots equals 1.34 times the square root of the waterline length in feet (HS = 1.34 x √LWL). So I will take it that BA has a waterline of 40ft which gives us a top speed of 9 knots (8.538149682454625 if you are being picky) or 10.357MPH.

Regardless of if Broad Ambition had 200hp all that would happen is  that the she would dig herself a hole.

If she maintains hull speed, her bow and stern are well supported by their respective waves and she can continue moving forward efficiently. But if she tries to go faster and the stern wave is pulled further aft by the lengthening trough of the bow wave, the stern falls into the hole, and she is left trying to climb up the hill presented by her own bow wave, which by now is relatively large.

However I wonder if this would be the actual result, because there is a way to get boats going faster than they should - semi-displacement hulls, of which Broom are rather well known for and if you look at the underwater profile of such a hull while they have a keel but as it comes to an end, the hull 'curves up' - it does not remain flat.  Broad Ambition's hull at the aft also does this, it reduces drag and a stern wave so with enough power, and some trim tabs to extend that 'buoyancy' of the stern and stop it digging into a hole so easily she could well exceed her theoretical hull speed.

The thing is, the extra power required per 1MPH of extra speed would not be worth it - indeed if you look at full planning boats with different engine combinations going from 300hp to 360hp will cost you a great deal more in terms of engine cost, but will get you 1 maybe 2 knots extra in speed.

I rather like this new BETA - complete with a cute Turbo and 85 lovely horses to let go:

beta85_he.jpg 

 

 

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Narrow boats on the canals had their exhaust exiting through the hull often on the side and just below where the helmsman stood.

They always were often standing in a plume of smokey diesel particulates, can't be heathy can it?

When we cruised through the Harecastle tunnel, near Stoke, you wouldn't want to follow a narrow boat, as the tunnel soon gets full of smoke. There is forced ventilation which helps.

Being GRP and with the potential to cruise faster, less water to displace in a narrow shallow waterway, we were always invited to go first. Great for us, but the narrow boats behind us now had some CO to breath.

 

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As far as I am aware we have the original engine and gearbox in Star Premiere. It is a Parsons Pike with a parsons gearbox. On tick over 900rpm we are doing around 6mph, so going up and down the Ant we are in and out of gear. Top speed around 9/10 mph is achieved under 2000 rpm although 2400 is available but with no appreciable gain. Very economical and pretty well bomb proof. If it ain't broke don't fix it.

000000 1960 Blakes Brochure.jpg

236mb.jpg

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3 hours ago, springsong said:

Very economical and pretty well bomb proof. If it ain't broke don't fix it.

Isn't that bloody lovely?

The Parsons Pike is the marinised version of the Ford 4D as fitted to Thames Trader lorries. Direct injection by a "jerk" pump, regulated by a mechanical linkage to the intake manifold.  Fitted also to the larger Freeman cruisers.

You are quite right, Springsong, they are un-breakable. 

If higher revs make no difference that is because the engine is big enough to try and push the boat over her hull speed. Maybe try a fine pitched propellor?

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6 hours ago, BroadScot said:

Look at those booking prices !!! :naughty:

 

Iain, did you notice they were per person prices.

Blakes did this for a couple of seasons. They had cases of people booking one berth and getting a shock when they found out they had to pay for the hire cost of the whole boat.

I think the brochure shown would be mid 60s as I remember cutting up a 1965 brochure (sacrilege) with that rope artwork, for a printing college project to design a brochure for the 1966 season.

Roy

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