Dehler 25 Lift keel Going Inboard

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fendtfan

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I have a Dehler 25 lift keel currently fitted with a long shaft yamaha 8 hp outboard. I am hoping to go inboard with a yanmar 1GM10. I am after some practical advise on how to go about this ie how to mount the engine what angle through hull positioning prop dimensions etc etc . Does anyone have a Dehler 25 preferably in East Anglia fitted with the yanmar who would allow me to come and take some measurements and photos to assist me. Thanks
 
Having looked at a few boats with 1GMs in, and been under way in a couple, I would be asking whether you really want this?
They are quite 'something' in what the auto industry calls 'NVH' noise, vibration, harshness.
25ft is quite small to be putting a twin cylinder diesel into though.
What exactly do you want from it?

Won't the prop be very vulnerable with the keel up in the shallows?
 
Was going to ask something similar, I would much prefer a simple outboard if it is positioned well on the Dehler. Inboards are grief to me, rotting exhaust elbows, stuff trapped around prop, water cooling, coolant, filters, batteries, sea cocks the list goes on...
 
Welcome to the forum.

The biggest challenge will be actually building engine beds and glassing in a stern tube and quite frankly it would be a massive and expensive project on a boat that does not really need an inboard. The engine and box is only part of the cost - shaft, P bracket, fuel system, exhaust system, electrics, engine box, insulation etc all add substantially to the cost and work involved. As suggested the 1GM is a wonderful little engine (I had one for 20 years) but is crude and noisy, particularly when installed in a light GRP hull.
 
Just wondering if the noise of the outboard is a factor for you.

If you currently have a 2 stroke outboard a 4 stroke will be a lot quieter .
 
Wing Mark said:
Having looked at a few boats with 1GMs in, and been under way in a couple, I would be asking whether you really want this?
They are quite 'something' in what the auto industry calls 'NVH' noise, vibration, harshness.
25ft is quite small to be putting a twin cylinder diesel into though.
What exactly do you want from it?

Won't the prop be very vulnerable with the keel up in the shallows?
Click to expand...
Thanks for your replies. The reasoning behind going inboard is mainly to allow better access via the transom. The boat is on a swing mooring and getting on and off from a tender is difficult because the easy access is denied by the positioning of the outboard. None of us are getting any younger. I try and fire up the engine as little as possible prefering to use the sails so i think we can put up with a little more noise, I am hoping going inboard will make the handling a little better currently the stern hung outboard fixed straight ahead makes manovering in any current very tricky. The dehler has a fixed section of keel about 25 cm deepwhich gives the prop some degree of protection. My previous experience of diesel engines is agricultural with lister petter and lombardini. I understood the Yanmar was a significantly improvement than the really old school stuff.
 
"Getting on and off" Perhaps you should try climbing over the side. On my 21fter this is the way I get on. Use the cabin top grab rails and side stays. You might also benefit by having a fender step. If guard wires are fitted then either try removing them or have an easy way to release the wires . (pelican hook).
As said fitting a one cylinder diesel does not seem like a good idea. Prop drag and vibration/noise would be a killer. ol'will
 
This theyachtmarket.com/en/boat-for-sale/2008386/ may help you as there are a couple of shots showing the engine under the cockpit and the shaft/prop. Looks like it is installed at the typical 10 degree angle to give enough clearance to swing the prop. This also might give you an idea of what a major task it would be to actually install a set of engine beds under the cockpit, cut a hole through the bottom of the boat, bond in a stern tube and a P bracket (all perfectly in line), install fuel tank, exhaust system, seawater intake, electrics including a starter battery, engine controls and switch panel. I note that boat has an access panel in the cockpit sole - I assume your has this also as you will need good access under there to do the work.

Don't know whether you have done the sums yet, but with all new you are looking at £6k+ just for the basic parts (up to £2k less if you can find a good used engine). However if you are spending that type of money then better to pay a little more and fit a Beta/Nanni 2 cylinder 10. Real step up from the Yanmar - 2 cylinder, freshwater cooled but fits essentially the same footprint, just a little bulkier at the aft upper end because of the extra cylinder. I replaced my 1GM with a Nanni 14 which is the same basic engine as the 10 and it was an easy change.

Make sure you choose the right reduction ratio as you will be limited in diameter of the prop. The Yanmar has 3 options and you will need the 2:1 as I expect there will only be clearance for a 10 or 11" prop.

You don't say what sort of experience you have if you are going to do it yourself, but TBH this is not for the faint hearted, particularly getting the beds, tube and P bracket in as you have no datum points to work from. When it is done at the factory, they will have done all this work in the bare hull using a jig to get everything in the right place before glassing it in. Would not be surprised if they then fitted the whole propulsion system before bonding the deck on.
 
Just to add another option - have you considered making a well for the outboard at rear of cockpit? That’s the arrangement I had on a SuperSeal26 (a similar boat to yours) and it worked very well. The prop was forward of the rudder and manoeuvred the boat well. Outboard was on rails and easily raised by a 3:1 purchase.
 
Good idea, but don't think it would work with the cockpit layout of the boat (see above link). Another alternative would be a saildrive - early Dehlers were offered with that option, but don't think many were built. Although potentially easier to fit than a shaft drive, the choice is limited and much more expensive.
 
Found a second hand yanmar 1GM 10 with control panel and f/r reduction box but no throttle cable or f/r lever at £700 and through hull shaft tube £125. P bracket not yet found . I am an experienced engineer and fabricator but have limited experience fiberglassing (more used to mild steel) The easist way I imagine would be to take measurements from a factory fit boat.glass in the engine mounts assemble the drivline which will give the positioning of the hole and p bracket . mount the engine and box, assemble the shaft, through hull tube and p bracket and glass into place while all is held in position. Then take it apart to do any further glassing and finishing. Sounds far simpler than it will turn out to be but it will make April when we get back on the water come all too soon. Currently the engine locker is a large empty storage locker with full access from above, batteries are set further astern either side of centre. Fuel tank can be positioned where the petrol can is currently deep in the starboard locker
 
OK Check that it has a 2.1:1 reduction and then put your boat and engine data into here vicprop.com/displacement_size_new.php/?m=1 to get your prop size. Then you can work out where the prop has to go to get the requisite tip clearance of 15% diameter. You will need a half coupling, shaft, GRP tube, shaft seal such as a Radice, P bracket and prop. That will cost you at least as much as your engine. Suppliers for stern gear try Lake Engineering or T Norris, either of which will advise and make what you require. Make sure the engine has mounts as these are expensive. Single lever controls and cables, another £200, Inlet seacock, piping, water strainer, anti syphon valve, water trap, exhaust hose, clamps and skin fitting, fuel filter and pipes another £5-600. You could get lucky with your fuel tank as I have an unused 25l Vetus tank in my garage looking for a home!

I did say that the engine itself is only the start of the bills! Even with your "cheap" engine your total cost will be well over £3K

BTW well worth getting the factory workshop manual for the 1GM as it will help you understand the engine and how to install it properly.
 
Interesting, I can see your thinking with that nice big boarding gate in the transom being unavailable.

I would be having a very hard look at moving the outboard to the side, might have to be a size down 6hp, with remote cables and a means to operate them from the cockpit.

And another thing, you won't need much of a diesel weep from this old 1GM for that small cabin to develop a certain aroma that will never be cured.
 
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fendtfan said:
I have a Dehler 25 lift keel currently fitted with a long shaft yamaha 8 hp outboard. I am hoping to go inboard with a yanmar 1GM10. I am after some practical advise on how to go about this ie how to mount the engine what angle through hull positioning prop dimensions etc etc . Does anyone have a Dehler 25 preferably in East Anglia fitted with the yanmar who would allow me to come and take some measurements and photos to assist me. Thanks
Click to expand...
I'm not going to get involved in the discussions over inboard or outboard, other than to say I'd specify an inboard over an outboard every time on a new boat, but would think long and hard about the work involved on one that's a few years old. What I will do, though, is question whether 10hp is enough for a 25' boat. Some friends have the same engine in a 24 footer, and find it could use more if the tide or weather are being unhelpful. I wouldn't suggest the 28hp I had in a similar boat, but reckon you'd be glad of 14-18hp if you're late getting into a tidal harbour, and there's no additional work and not that much additional cost.
 
It is a very light boat (a trailer sailor), only 1.5 tons and the 1GM was originally fitted as an option - not much space for anything bigger except a Beta 14, but really does not need it.
 
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