Diesel or Petrol?

SteveGorst

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Our old volvo MD5c + saildrive whilst working ok at the moment must be reaching the end of it's life shortly and I am starting to think about it's replacement. Having looked at Yanmars and Volvos plus saildrives and their prices compared to the value of the boat it suddenly occured to me, what about a shiny 10hp 4 stroke outboard.

On a lifting bracket they can be lifted clear of the water while sailing enhancing the sailing performance. They are lighter again, enhancing sailing, quieter, and a lot cheaper. On the down side petrol cost more than diesel, but is this going to last? I would also imagine they are more thirsty than diesel but would I spend more on running than I woud save on capital? Are they that much thirstier. For say a 15 hour trip pushing a 26ft yacht at 5 knots how much fuel do you imagine I woud have to carry?

If i took out that lump of a diesel engine i could also make better use of the space released.

Any opinions welcome...

Steve
 

Spyro

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There was a very good article in last months PBO where they tested outboards comparing 2 and 4 strokes and giving fuel consumption figures. Most were around 10hp. may be a good idea to try to get hold of a copy. If you are doing 15hr trips quite often I think it would work out quite expensive. I think fuel consumption was around 1 gallon per hour so 15 hours at 5 pounds per hour would soon add up. But I can see the plus points of your argument. weight/space/cost and ease of fitting and noise levels would be less as well. Downside would be trying to motor in swell or chop and keep the prop in the water
Probably best hearing from someone who has removed a diesel and put on an outboard
 

SteveGorst

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No I don't do 15 hour trips often but we do go to the Isle of Man sometimes which under fair conditions is between 10 and 12 hours. When we motored with red diesel it cost about a fiver but with a super light engine the amount of motoring we do could be well reduced.

Thanks for letting me know about the article I'll try and find a copy.

Steve
 

bruce

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you also should look at boat balance with the loss of the weight of the old motor so low in the hull, make boat more tender....also, do you have a cabin heater and cooking stove that uses diesel....
 

SteveGorst

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I'm not about to rip it out or do anything hasty, i really do believe if it aint broke... You should see my cars, these Mitsubishis just won't die /forums/images/graemlins/smile.gif But it does take a bit of time to start on a cold day and has recently shown signs of overheating. I have changed the impellor and this weekend I'll be looking for blockages. I'm just pondering over the future really.

Steve
 

SteveGorst

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no we don't have anything else that uses diesel, luckily we live 2 miles from the boat so don't spend winter nights aboard. I'd have thought the engine was only just below the c of g but I could be wrong.
 

alahol2

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Used a Yam 9.9 4 stroke for 12+ years on our last boat (32ft Iroquois). It was a gorgeous engine that never once gave us any trouble. If I remember correctly it used to give us 5knots at about 3 litres per hour. One drawback is that they are very sophisticated engines. Like modern cars, if they stop going there's very little you could do. One tends also to just take it to the dealers every year for its service, which can be costly. You'd want to find a way of storing the fuel so that there's no possibility of fumes getting inside the hull. I just went through the same thought process as you before deciding to go the replacement diesel route.
 

fireball

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We had a 15hp 4 stroke on the back of a 22'er ... the issues we had were:
1) In a chop the prop came clear of the water
2) When trying to berth you had to be head over the stern to control the throttle
3) The fuel didn't last too long
4) It had to be padlocked to the boat so it wasn't stolen
5) It unbalanced the fore-aft trim
6) As it was offset to port it dragged in the water on starboard tack - even when raised
7) When the electric start didn't work it was very difficult to use the hand start on the end of a wobbly bracket

The positive points:
1) tight circles were a dream - just turn the engine around and forget the tiller!
2) winter storage was simple - take it off the bracket (2 man job as it was heavy) and wash out, then in the shed

erm ... thats it!
We actually removed the outboard and replaced the Jap inboard (with a big end that was a little loose) with a volvo MD5a ... what a difference!! the maneuverability wasn't quite so good, but being able to standup in the cockpit whilst coming alongside was wonderful!
The weight of the outboard was quite horendus, possibly we were over sized, but that is how it came from the previous owner.
The fuel tank had to have its own locker and made the rest of the boat smell of petrol fumes for a bit...
I'd get your volvo engine serviced and possibly try and clear out the cooling system - there is another post recently about that ... you could always fit glowplugs if you find it doesn't start when cold (I think PBO did that in the current edition)
 

gorb

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Only comment I would add to all the others is that you should be aware that the availability of petrol at the dockside is much poorer than diesel. If you do longish trips and have to motor then you may face long walks carrying petrol cans!
 

Joe_Cole

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Fuel consumption is considerably higher with an outboard. Apart from cost this affects your range. Don't forget that many destinations don't have petrol available at the waterside; diesel is usually readily available.

Increased quantity of petrol means more storage problems, and of course it's potentially more dangerous than diesel.

Arguably diesel engines are more reliable.

Outboards usually generate only small amounts of electricity. (Typically 6 amps)

Particularly on a lifting bracket outboards are more vulnerable to theft.

I'm not sure that outboards are necessarily quieter; I think it depends on the setup.

Outboards aren't very good in reverse; but again it depends on the set up.

I've got an outboard; I'd like an inboard. Care to swap? /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif
 

SteveGorst

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Thanks for sharing your experiences. I'll not be in a rush to replace the old volvo now. I'll have to be a bit more patient with repairing her and take a look at this post you mentioned about clearing out cooling systems.

I remember now reading in Ellen Macarthurs book how she got in a bit of trouble off the Isle of Man with her Corribee due to the prop not staying in the water. I never used to have that problem with my Seahog fishing boat but I guess yachts are not designed for outboards.
 

SteveGorst

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yes I've just had a look at their website. If it does what it says on the tin I'll give it a go. I wonder how you'd apply it to a raw water cooled engine. I can imagine my engine being full of mussels. When we took the boat out for the winter the saildrive was absolutely full of them.
 

fireball

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We flush the engine through by taking off the raw water inlet hose and putting it in a bucket of water (with a mains fed hose on a spray gun to keep the bucket topped up!). I would imagine that this could be done in a similar way.

As a matter of interest, this was how we discovered our impellor was knackered - cos it wouldn't pull any water into the system, and we had not noticed as the force of the water through the intake when the boat was afloat compensated for the lack of suck of the impellor!! - but that is on the new boat with a Yanmar engine.
 
G

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Previous boat ...

The old Vire was sent to the Great Engine Bed in the sky when it gave up its last !! So I looked for alternative ... wanted a Petter Mini 6 ... (Boat was 23ft Snapdragon).

In the end I fitted a lifting bracket and a 7.5hp Mercury Saildrive. Marvelous - quieter, safer than a petrol IN the cabin ... BUT what a pain to lift on and off ... couldn't leave it on - someone would have pinched it.
Prop would come out of water when in reasonable swell / waves ....
The prop wash was non-existent over rudder ... ok ahead, but astern !!

So upside : Quieter and easier to service etc.

Downside : More expensive to run, prop would come out of water, b......y heavy to lift on / off.

So I then cut an engine hole down through cockpit floor and sited the engine ahead of rudder - with enough swing to 'steer' by .... WOW !!! The manouevrability was unbelievable .....

Sold the boat with it a few years later .... and I believe the next owner reverted it to the lifti8ng bracket and rebuilt the cut out cockpit floor. (I did give him the cut-out just in case !!)

IMHO - my next present boat has in inboard diesel and I am much more happy ... the advantage of inboard to me far outweighs any advantage of the lump hanging on the back-end.
When the old engine retired in present boat - I looked at O/bd and bracket - was offered excellent deal at £400 engine and bracket from a dealer .... but finally opted for another inboard direct replacement .... I am very glad I did ....

/forums/images/graemlins/tongue.gif
 

oldharry

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Re: Previous boat ...

Agree totally with Nigel: Boat handling with an outboard in e.g. the confines of a marina, can be a nightmare. Prop out of the water in anyhting more than a moderate sea. Nothing like as much thrust when you really need it. Outboards vulnerable to theft, damage, swamping, falling off. Not much quieter than a good modern diesel engine.

And COST. Ok its a cheaper engine to start with, but run the average 2T 10 hp for 15 hours you need to be carrying in excess of 17 - 20 gallons of fuel (at forecourt prices!) A 4 stroke will fare considerably better, but even so you could need 10 gallons +.

And where do you buy petrol other than at rip off marina prices: most marinas passed the £1 litre mark long since. And carting 10 - 20 gallons of fuel out to the boat from the local garage is a total pain! Worse still if you are away from base, do not have the car, and have a one and a half mile walk to the nearest petrol station.

Also as Nigel points out, a 10hp outboard is not the sort of thing you carry around as hand luggage! Unless you have a crew of fit young men that is....
 

dmayes

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Spare fuel tanks are reasonably cheap. You could have a few tucked away down below giving you a good reserve, easy to change too when you run out. Fill them up at the cheapest petrol station too, you don't have to use fuel pontoons and pay the premium rate. A lot of smaller yachts use outboards like this by default and if you get an electric start with remote controls, you can use these from the cockpit same as an inboard. You will get the prop leaving the water in a heavy swell but so do smaller yachts and they seem to cope. One advantage is being able to take it home for repairs/servicing etc.
 
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