Change from Outdrives to Twin Shafts and Props

[PCUK]

Thanks for the info - there is so much knowledge available on here.

In the 4 years I have contemplated this project I have amassed a library of books and technical information from the 'web but know I will need expert technical assistance at some point and have budgeted for that - I would like to have a marine engineer / surveyor 'on board' to confirm my ideas and processes prior to my doing something silly.

Definitely avoiding chandlers! Fortunately I'm moving from London to the South Coast so hope to find the specialist suppliers I need down there - there's naff all up here except expensive boatyards on the Thames.
Most of the materials I need seem freely available on the internet.

The superstructure modifications, (additional frames, ply deck and stainless tube reinforcement) engines / drives / fuel tank installation use 'off the shelf' components - the fun part will be making up the various period related lights, masts, deck equipment etc, that's what I'm looking forward to the most; i.e. a searchlight made from a pressure cooker vessel, suitably drilled and tapped for mountings with a sealed beam unit; a demountable radar mast, a mast for multiple 1960 era 'Perko' nav lights, of which a master mould will need to be created for resin cast replicas; mounting for (replica) twin 50 calibre M2 machine guns in the bow etc....

We love you man!!!

 

[ChromeDome]

When looking you'll soon see a Project 31 with twin sterndrives and 2x70 hp Volvo diesels - for sale.

That kinda power would suit the indicated use quite well.

 

[Freebee]

Think about the fuel- the number of marine outlets for petrol is very reduced and if you cannot get it locally you will be hauling jerry cans from tesco, I have done this it gets quite wearisome quite quickly, diesel is a far better option and safer.

 

[penfold]

I'm happy rebuilding the B30's but if too far gone I'll buy alternative engines (petrol)

The boat weighs 4 tons and has semi displacement hull - a couple of outboards won't quite work for me

The budget is £20k - the boat won't be worth even half that in the end but that's not what its about - its a retirement vanity project.

It will use OPEC-pleasing amounts of fuel even at displacement speed; when your heirs come to sell it they will curse you for fitting petrol engines. Opportunities to buy petrol at the water side are rare, lugging jerry cans around will get tiresome very quickly and garages can get sniffy if you want to fill more than a couple at a time.

 

[scottie]

Great to hear that you are doing the job just because you want to! I've done that all through my boating "career". Personally I would keep looking for drives as this will be a much easier project. Don't fixate on any particular make or model, just find a pair that will do the job. Don't involve professional outsiders in the project as that will make it too costly. Everything you need to know/learn is available in books and on You-Tube which is a fantastic resource in finding out how to do things! You will have a comprehensive set of 'experts' here with varying degrees of expertise, just sort out the wheat from the chaff! As a new member you will probably not be able to post pics until you have made a few posts. Once you can get some pictures up the advice will be more targeted and accurate. If you are a practical type you will love this project. By the way the most important rule of boat rebuilding is to never buy equipment from a boat shop. Always find your local specialist supplier. Hydraulics, stainless steel nuts land bolts, fibreglass, timber, plumbing, electrics, etc. etc.

Thanks ChromeDome. Very useful info and in line with my thoughts re tubes / shafts etc.

Will try and post some pics after checking the process on here.

I intend using the boat as an occasional weekender, river cruising with a few estuary / coastal transits - to be honest its more about fixing it up than using it - it's more of a fun learning project than an earnest, determined must-get-it-in-the-water-and- into-the-Med- asap type project. Its a bit like a Series Land Rover project; fun to do up and light use now and again.

Not scared of using petrol; will have blowers and a full check with hatches open prior to start - planning on vibration free fuel mountings as much as possible and automatic engine bay extinguishers, remote fuel shut off. I don't need a lot of range so might opt for smaller baffled and foam filled tanks (similar to racing car types but larger).

If money were no object I would go for twin Detroit diesels and Jacuzzi waterjets - if I could find them at a reasonable price. The 'jets have their own issues but it would be interesting planning the instal!

It does sound a bit unusual but as someone once said: 'Charlie Don't Surf!' (there's a clue).....

I retired about a dozen years ago and at that time the Aq170 was well past its useby date and parts were rare and decent manifolds like rocking horse poo
keep looking and dreaming but the reality is not a dream but a nightmare waiting to engulf you with finance and other horrors
perhaps test the market and see what value there is in selling the hull and buying something at least further on in the process
there is a long thread re restoration of boat with AQ130 engines which is required reading

 

[Freebee]

Let me try and inject a note of realism here I don't want to dash your hopes, but you have been given a bare hull which had outdrives , you want to employ somebody to fettle the hull from drives to shafts - apart from blocking up the old holes, you will need to strengthen the hull where you will break through for shafts because the hull was not made for this, create new bearings and seals for the shaft and p brackets underneath, fit new steering gear and rudders, then new engine and gear box mountings in the hull and adaptors from engine to gearbox - well that's going to cost £k's.

then you need to buy 2 gearboxes, shafts and props to match a pair of B30 engines possibly 50 years old- I think these are the weak spot in your plan. If the engines let you down a lot of your expenditure has been tailored to these engines, props, gearbox adaptors etc. this is a lot of investment in time and money based on fitting these old engines,

All of which at the end of the day is being spent on a boat that will not have much value.

do a list or better a spreadsheet.................... look at your costs before you start, probably better to dump your hull go find a boat with twin diesels on shafts ready made and go boating rather than boat building.

 

[PCUK]

Don't worry, it's a fact that anyone on here trying to do something a bit interesting will find people waiting to p*ss on their chips. Projects like this can and are done on the cheap and can also be spectacularly well done. I've been doing it all my boating life.

 

[gordmac]

If you want to do away with outdrives maybe a single rather than twin shafts using one of your engines with the other for spares is the way to go?

 

[scottie]

Twin engines + tubes & shafts + gearboxes + reinforcement of hull + brackets + rudders/hydraulics + rebuild of engine bay/mounts + cables and more. A lot to spend time on
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It's an exciting project, hard to judge if the budget is sufficient without knowing the boat and your expectations for the result. Or your schedule.
Pictures would be great.

31' Semi-planing and with 2x170 hp sounds a bit unusual. How do you intend to use the boat?

Volvo's B30 was made from 1968 to 1975 (a fairly short production run) and was basically a cast iron 4-cylinder B20 with two extra cylinders. Made in 117-175 hp versions, the marine version was marketed by Penta with 3 downdraft carburettors and a hotter camshaft to make 170 flywheel hp. Known to consume a lot of fuel.
Not many were fresh water cooled and most have long since rusted away.

Modern 4-strokes are in many ways better (and use far less petrol) than old car engines that were marinised, and spare parts for marine B30s are difficult or impossible to find.


I wouldn't rule out outboards completely. They are complete units with engine, gearbox, shaft, propellers, steering and all. Good access to service and maintenance and easy to replace should the need arise.
In addition, they solve the safety issue when petrol engines are in a closed space inside the boat.

None of the ones that left the factory which would be now 50plus years ago were fresh water cooled and salt water makes a real meal of manifolds blocks and circultion pumps

 

[piratos]

Don't worry, it's a fact that anyone on here trying to do something a bit interesting will find people waiting to p*ss on their chips. Projects like this can and are done on the cheap and can also be spectacularly well done. I've been doing it all my boating life.

Well spoken. Can only say listen to those who can assist and forget those trying to decline the project. Projects are for people with guts! In this forum is also a guy who totally restored a wooden boat in Greece. Check out his rebuilt project