two engines or one plus kicker

Re reading the posts above I just noticed, that the engine bed is thought for a "sterndrive"!!! In this case a CPP is not available. That makes the outboards a more sensible alternative.
In addition to the facts Will added.

If the intended use is a very intense sort of cruising, the common single Diesel, shaft, CPP, would be by far the best choice in every aspect. Even (no especially) in a price comparison.
Otherwise, see above....

In the mono vs twin dispute we should never forget, that commercial Diesel installations in general have much beef. (displ. to power ratio) A common yacht arrangement has´nt. But the outboards are neither the best examples in longevity! The average boat Diesel lives min. five times longer than the average OB. (make a cost comparison over the intended lifespan)

Regards
Richard

 

Yes.... the idea of designing a boat with the intent to re-power it in future, with a different engine setup than the original, seems a bit odd. And, I've only heard of one sterndrive with a CPP, and it's not entirely clear whether that particular model is real or just some engineer/marketer's dream.

A valid point, Richard. However, I'm not sure how applicable this argument is for the case of a typical pleasure cruiser, which may only see 100 hours a year of running time. A good outboard can easily live for 20+ years without major servicing, used this lightly. A diesel in similar use- despite having rung up nowhere near its achievable running hours- is probably going to need major servicing due to corroded heat exchangers, deteriorating gaskets, etc. at about the same time the outboard craps out for good.

Of course, if you run the thing hard and fast 14 hours a day year-round, your outboard will probably be toast in two or three years, while a good diesel (despite costing at least twice as much up front) might get to ten years or so before needing a serious overhaul.

Having said that, I tend to come out strongly in favour of inboard-mounted diesel or gasoline engines once you get over about 180 hp. The outboard's advantages of light weight, low cost and simplicity are largely defeated when you make them too big, and while all that weight aft is OK for a fast boat, a couple of quarter-tonne engines hanging a metre off the transom can seriously hamper low- to mid-speed performance in some boats. Outboard lines are redesigned on a fairly regular basis, and some specialized parts can get pretty scarce after a while. But there are dozens (if not hundreds) of aftermarket dealers and suppliers that can get you OEM-quality or better parts for your 20-year-old 4.3 V6.

Whether you can find a sterndrive that has a chance of surviving extended saltwater use, well, that's another story. I've heard good things about the Volvo composite-casing unit, but it hasn't been around long enough to say how long it'll live.

 

Matt
>>>A valid point, Richard. However, I'm not sure how applicable this argument is for the case of a typical pleasure cruiser, which may only see 100 hours a year of running time.<<<

For exactly that reason I asked for the intended use, in the post above!

 

thanks again

The boat in question is the Power 3 at the following link.

http://www.selway-fisher.com/Mc2130.htm

Hope it comes up ok. I have spoken to the designer about extending and widening it (30'x9'6" ish) and he will do the necessary to adapt the plans for a suitable renumeration as would be expected. As you will note, an option for it does include an outboard well so there is scope and some intention for outboard power there although inboard is anticipated.
My thinking thus far has been to build it to incorporate two full length LVL stringers (have spoken to the designer about this also and he has been very patient and helpful). If I build in an outboard well designed to take a 'big and little', I can get it on the river with just the little to start with. Once we venture further afield, perhaps move mooring downriver on the estuary, there will be a need for more power. That is when the big outboard comes in. If by then, we have decided to go for a diesel sterndrive, I have the necessary strength in the stringers to sit it on with modifications to the transom and a bracket for the little outboard. If we decide to go with an outboard, she is practically ready to have one fitted on.

Our usage will evolve from occasional river trips with scope for occasional estuary/coastal trips to more extended cruising much further afield when we retire (I am already 50). I realise that in 3-5 years time, I may still have a lump of plywood upside down but it will still have inbuilt options for us. By then, we may have outgrown the capability of our current boat and will have a better idea of what we will want to do with the new one and what power set up we want. I have this vision of it all but it does come out on here very well and the reality will change no doubt. I don't see us motoring flat out for long distance at sea, more of the occasional hop from one estuary to the next. This is why the big outboard seems more logical with the initial smaller outlay for something that may not get 100s of hours notched up on it. The list price of a Tohatsu 115hp TLDI is less than £9000.

You have all been extremely helpful, for which I am very grateful and I hope the above gives all a clearer idea of what is in my head.

arthor

 

So you have a design drawn for a single INBOARD! A perfect choice. Why complicating it?
A sterndrive combined with a aft cabin is at least not very clever!
A outboard well in that position is´nt a perfect solution either.
WHY?

A proper Diesel with a CPP will be about the same price range as your two outboards! But it will live for ever and another year. And (only with a CPP) you have never any hassle going slow or fast, right as you want.
All the Scandinavian fishing fleet is equipped with CPP´s. They need trolling at very low speed for long times, but then they have to go home to land the catch, pretty fast. All with the same single engine. Thats proven since ages.
And Fishermen do´nt waste money. Nor do they rely on unproven stuff.

Lookup "frenchmarine.com" and "EP Barrus" both in Britain. Both have prices on their site! Look for something in the 4,5 liter class, like John Deere or Deutz. These engines at 100 - 120 hp live forever, when combined with a CPP. That will add another 6.000 quid to you bill. Choose a "Hundested", worth it´s weight in gold. That may come out a tad over your arrangement with two OB´s. But you, and your children, will never have to replace it, and sure you´ll notice a substantial difference when bunkering.

Give it a thought! You´ll end up happier, believe me.

Regards
Richard

 

Arthor,

You're looking at a relatively heavy boat, drawn for a single inboard, double-chine hull (sort of semi-displacement, probably won't plane easily) and with a relatively low cruising speed.

If you're really set on outboards, you can probably make them work. But I suspect that this boat will run better (and be better balanced) with a single inboard diesel, and given the way you're expecting to use it, a CPP is probably a sensible drivetrain choice. Outboards are generally meant for light, fast boats- a look at their RPM ratings, gear reductions and maximum prop diameters will make that painfully clear.

I'll probably take a bit of flak for saying this, but you don't really have to drop twenty grand on a "proper marine engine"- I suspect you could find a used tractor or industrial engine, have a good mechanic overhaul it, and buy a suitable controllable-pitch prop and gear, while spending less than (or comparable to) what you'd shell out for a suitable outboard. If you're really cheap, pick up a second- or third-hand F/N/R transmission and fixed prop, but be aware that such a setup won't do low speeds as well as the CPP.

 

No Flak from my side Matt.............

I just compared his OB at 90 horses with a inboard at 100 and found both are 100€ per pony. So, the second OB should pay half of the CPP already.
Sure there are second hand engines on the market, some unused at 3.500€ and less.
here:http://www.dieselenginetrader.com/index.cfm
The CPP though has to be taylored, means new.
But the real smile comes when bunkering! or better said when not....

 

Another factor in the one or two set up is that in most all installations, there is only one fuel supply. Often there is only one electrical installation for both. Many, if not most problems with any engine installation is with the fuel or electric equipment and these are not usually separated for twin installations. A failure in fuel or electric affects both engines and kills the reliability factor. With two engines, there is redundancy but also twice the failure rate.

If you've got to have both belt and suspenders, I'd prefer the one main engine with a kicker solution with the kicker having its own small fuel tank. I'd probably not even mount the kicker for routine use. One friend has such a set up with the steering not coupled between the engines. When trolling or just running slow, he drops the kicker in and steers with the big one, using about 1/3 of the fuel that the big 150hp would. Not an ideal set up but, it works so well he is not inclined to change it.

 

Ok - having looked at the website, I would have to concur with the others.
This boat is set up to operate with a small inboard engine. A little diesel would be ideal. Whilst it's true that diesel's don't like to operate underloaded for extended periods, I'd be inclined to go for a straight shaft installation. CPP is an expense I would do without - just give the engine a decent run under load every now and again.
Whilst the flat run aft suggests that the boat would sort of plane ok, the double chine is certainly not ideal for doing so - it would be wet and very likely suffer somewhat from dynamic instability. The sections also look very flat throughout, so it would likely pound quite badly too.
If you want a boat that goes fast, choose a different design.
On this basis, an aux. outboard of around 25 hp, with a lowish pitch prop, would be plenty and could be mounted on a simple bolt-on bracket. Steering can be done using the existing rudder, though obviously a separate throttle would be required. To simplify the refuelling, you could opt for one of the Tohatsu diesel outboards, though I would agree with Tom that you should serve the two engines from separate tanks.
Initially, you could indeed leave the main engine out altogether and just use the outboard. You would probably have to add some ballast to account for the shifts in weight and to offset any lost stability, but otherwise it should be no real problem

 

My Croatian neighbor is a professional fisherman. In his case that means he has 3 big trawlers rummaging the Adriatic seabed 6 days a week unless there are repairs or maintenance to be done. He does that for as long as I live here, so at least 15 years.

For his very limited spare time he uses a 30 ft Italian built open sports boat moored next to mine. It is powered by a Merc Optimax 225 2-stroke engine and since he once damaged the prop, a 10 hp for emergencies.
Before that he had a big Yamaha 4-stroke but he wrecked it when leaving the bay at full throttle a few years ago. He claims the Merc uses less fuel and is more reliable because it has fewer parts.

He watches me changing oil, cleaning props, replacing zinc anodes etc. and shakes his head: he does none of these things because his engine doesn't even touch the water so it looks as if it was installed yesterday. There is of course the fuel bill: where I fill up once in spring he starts every weekend trip at the fuel station.

But all things considered he is not the fool I though he was.

 

Hmm

Just when I was thinking that I am indeed a looney, CDK comes up with that response that indicates that someone somewhere sort of thinks the way I do.
I have a feeling that if the boat gets built, it will end up with an inboard diesel and maybe a little kicker.
Of course another option is to stick with my current boat and set it up the way I want. Because of a big 6 cylinder volvo, I would not be able to lower the pilot house(??) floor so I was thinking that setting it further back and using a V box, I could free up space forward. I know that will shift weight backwards ( I am assuming with a vee box, you effectively move the engine back one full length and a bit more). The batteries and water tank is aft at the minute so shifting them forward might go some way to distributing weight.
My current boat is a Fjord 27 and some have been fitted with up to 200hp engines which give it very passable coastal performance. This means that I already own a very good hull but just need to shift the engine backwards and beef it up.
All the responses I have had seem to indicate that my build plan is not such a good idea. This forum is excellent thanks to people like yourselves. I was not looking for a favourable or otherwise response but a response and that is what I have and will adapt my plans accordingly. Does anyone think that moving the engine location on my Fjord is feasible then??

regards

arthor

 

Feasible maybe.
Sensible - no.

There are a myriad of different boats out there, new & 2nd hand. One or more will almost certainly fit your needs. Go buy one.
Pouring money into changing an older boat into something that its not meant to be will see that money taking a one-way trip.

 

There is however a major difference (at least one) between you and my neighbor. I used the phrase "his very limited spare time" where you in post #1 are dwelling the northern hemisphere. My Croatian fisherman jumps aboard, picks up his wife and kids from the pier and leaves the bay like a bat out of hell, heading for the fuel station. When he returns a few hours later, he tilts the engine while answering a call from his cell phone and a few minutes later I hear him start his car and leave. Sometimes he doesn't get near his boat for months.

I concur with Willallison but at the same time know that there are other factors playing a role. A decade ago I took a potential buyer to our boat because I thought we didn't need it anymore, but my wife whispered "don't do it, I love this boat". So I asked a ridiculous price, the guy said no and I started making plans for replacing the twin stern drives with something completely unique that still isn't finished.

You have a sturdy Fjord 27 with a prop shaft. Newer boats look better but have an eggshell hull compared to your boat. If you really intend to use it like you describe in post #1 and have time/money to complete the conversion, installing a proper diesel with a V-drive is worth considering.
Your retirement is still several years away and in the meantime gasoline will become a still more expensive commodity. Imagine how long you can travel on a tank of red diesel!

 

CDK

this will be the first time I contradict you (as far as I remember).

But I have my doubts the Fjord will do good with shifting the weight 2 meters aft. And we should not forget, that some people enjoy the task of re- engineering and redoing everything on their boat, to a lesser extend than you.

When the original plan of building and cruising was´nt completely misunderstood, the boat will see quite a bit of travelling, and is not thought to sit in the marina for ages.
If so, a beefy (not high power) Diesel and a controllable pitch prop, is the way to go. The fuel savings alone will pay quite soon. Let alone the longevity of the engine.
When a possible engine failure is a real concern (of course it can happen, and if only a net blocks the prop), a decent kicker OB will do whats needed, and does´nt cost a fortune when replaced after 15 years of rusting away.

Regards
Richard

 

Just a simple question whose answer somewhat interests me:

Which manufacturer would offer a CPP in a suitable size for a 27' power boat? Aren't the minimum propeller diameters somewhere around 70cm?