type of engine

[IzzyDeadyet]

Can anyone please answer more dumb questions. This time about engines?

The old and cheap 20-24 foot yacht that I'm looking for but haven't found will, I think, have a choice of engine: inboard, outboard or none at all. If it's an outboard I'd want it to be 4 stroke.

In my ignorance I assumed inboard engine meant diesel engine.

But yesterday my car mysteriously stopped as I was driving past a small boatyard and I was forced to go and look at boats while it had a rest. I was very surprised to see that what I had taken to be a demolition notice pinned to a particularly decrepit 30 foot yacht was in fact its sales particulars I had a good laugh at the asking price - the owner obviously has an outrageous sense of humour.

But what really surprised me was that the boat was fitted with an inboard PETROL engine and now I'm even more confused. I thought only diesel engines were fitted because they were more reliable.

Are there lots of petrol inboards out there?

Would you recommend them or should I stay well clear?

What would be your preference on a 24 foot yacht:
diesel inboard
or petrol inboard
or petrol outboard?

As always your advice and comments would be appreciated.

Meanwhile my search continues.....

 

[boatmike]

Petrol inboards are a substantial fire risk. Avoid like the plague. Petrol outboards are a risk too but in this case you can usually minimise the risk by NEVER taking the engine inboard and storing all fuel in an external locker where no electrics or other fire hazards are present.

 

[Evadne]

Preference would be diesel inboard, the Yanmar 1GM and the smallest Beta are the most common new engines fitted, with Volvo fairly common and an assortment of others. Second best would be a 4-stroke petrol outboard in a well.

An outboard can be not very useful in a heavy sea (when you should be sailing not motoring anyway), other disadvantages depend on the boat configuration. Advantages are that you can take it home to service it and you will never fill your bilges with smelly diesel or engine oil.

Petrol engines were fitted on older boats because marine diesels were large and heavy, before the Japanese turned their attentions to them. It is rare or quirky to find them fitted as new in the last 20 years. Some Motor boats have petrol engines, but they are more powerful than the one in an equivalent sailing boat and not really relevant. You can live with petrol, but the big danger is petrol vapour pooling in the bilges. Motor boats fit "blowers", fans to evacuate the engine room, but I suspect the key to not blowing yourself up is to become paranoid.

Happy hunting.

 

[spannerman]

There is a lot of crap written about petrol engines having a tendency to sponataneous combustion, actually any large insurance company will tell you that there are more fires on diesel boats. and they burn just as well as petrol! The reason is simple, when you have petrol you take refuelling and maintenance more seriously as you know that petrol is more inflammable. I see boats every day with diesel in the bilges and leaks on the engine but folks don't give it a second thought, but diesel will burn very readily once its heated sufficiently.
A trip to any large marina in Florida will reveal that most boats up to about 35 ft have huge petrol V 8's in them, usually two sometimes three, and in a society that loves to sue, you wouldn't be able to give petrol engines away if they were so risky.

 

[Evadne]

There are more fires on diesel boats in the UK because most boats are diesel powered. Most parts of a boat are highly flammable and most fires are electrical, so I agree that the type of engine isn't relevant. The difference is that while both will burn if you set light to them, diesel vapour will not ignite in the absence of a flame unless heated to its flash point, e.g. a leak onto a hot exhaust manifold. The vapour from a pool of cold diesel is not flammable, you can hold a match over it in relative safety. Petrol has a flash point below room temperature and it mixes readily with air to form an explosive mixture. Being heavier than air it will flow into the bilges as well as form over a pool of liquid. A spark, however formed will ignite the mixture. This is an added danger of using a petrol inboard.

I agree that petrol (like plutonium and LPG) is not dangerous as long as you are careful and sensible, its just that not everybody is, you have to be more careful with petrol than you would with diesel to achieve the same level of safety, and we all make mistakes from time to time.

 

[Colvic Watson]

Petrol inboard was common on smaller pre - 1980 craft as the diesels of the time were too large and heavy. Many have been re-engined with small diesels now. Petrol inboard will save you about £1500 on the asking price but cost you £4,000 to replace. The petrol inboard may occasionaly work so it is not a complete waste of space (howls of protest from forum users with WONDERFUL and RELIABLE petrol inboards). Main problem is that a damp atmosphere and inboard petrol engine go together like King Herod and childcare.

Outboard's are fine up to 22 foot - but there is usually significantly more weight in a 24 footer. Having said that an outboard can help with steering under power. Here are my tips:

1. Buy the boat you like regardless of engine
2. If it's a got a diesel - get it serviced and away you go
3. If it's got an inboard petrol - fit an outboard as well!

Good hunting

 

[oldharry]

Being just in the process pf converting my boat from petrol to diesel power, i would go along with most of what is said above, except for the following points:

Petrol engines are much lighter and quite a bit smaller per hp ouput than diesels. An engine like the Vire 7 or 12, or the Dolphin 12 are so light they can virtually be picked up by one person. Whereas equivalent power diesels may be three times the weight, so that if speed and weight are considerations for racing, petrol has a lot going for it.

Petrol boats do not blow up. They are set fire to by careless owners. So are diesel boats. Most fires are electrical in origin anyway, but even so some insurers balk at petrol engined boats. The problem is that a fire in a petrol powered boat, whether inboard or outboard, is more likely to have catastrophic results if the fuel becomes involved. However diesel will too burn very fiercly once it is warmed up a bit - it is a fuel after all!

I have owned many boats with petrol auxiliaries, and both the boats and I have lived to tell the tale! The biggest problem with petrol power is that relatively few marine outlets actually supply it - and those that do know very well how to charge for it. Expect to pay AT LEAST £1.00 per litre - yes £1.00 - if you buy it waterside. As you are not supposed to transport more than 10 litres in your car other than in its fuel tank, this actually presents the biggest problem for petrol engined boat owners.

 

[Evadne]

I can almost pick up my 1GM8 (including gearbox), I'd guess its of the order of 60kg, I definitely could when I was 10 years younger. If a Vire is 1/3 the weight then it would be a one-handed pick-up!

Incidentally nobody's mentioned diesel outboards, they are still being produced as far as I know, not that I'd fancy hanging one off my transom.

 

[SlowlyButSurely]

There is one other factor that has not been mentioned which is that a boat with an inboard petrol engine is virtually impossible to sell. So unless you are going to keep it forever it's a point worth considering.

 

[SparkyLeisure]

I have a Leisure 23 fin keel with a Volvo Penta MD5b 7.5bhp diesel inboard with saildrive. It will cruise at about 4-4.5 knots on engine power and thats not forcing or running the engine hard. It is salt water cooled (downside) but incredibly economical.

I picked the boat up in Kip, Western Scotland and motored back to Donaghadee, Northern Ireland approx 89 nM using about £4.00 of diesel (red).

The engine was overhauled in 2001 and the only problem i've had is a leaky salt water intake which volvo have now re-designed. I feel it is a little underpowered but it is an auxillary engine, after all it is a sailing boat........
Feel free to comment

 

[DavidTocher]

I have a Vire BVR petrol inboard engine in my boat. The insurance people weren't interested enough in the 'extra risk' associated with petrol to increase the premium. Most of the people who advise against petrol will use LPG for cooking which is even more of a risk.

David

 

[dickh]

Everything that has been said is relevant, but bear in mind that two identical craft, one with a diesel and one with a petrol engine; the petrol engined one will be cheaper by up to £3000..... As long as the installation is up to the latest regulations concerning petrol engines, and if you are on a budget, and are prepared to carry the petrol on board in cans, then go for a petrol engined one BUT be careful....... Don't forget when you sell the boat, you also won't get a lot for it unless you re-engine it.
I did exactly this a few years ago, bought a cheap Halcyon 23, upgraded the fuel supply system to the surveyors recommendation(copper fuel lines, all compression fittings, added a fuel tap + other bits I can't remember) and then used it safely for 3 years before selling it. It was reliable, quiet, used very little petrol & could be handstarted if necessary.
The Broads regulations will give you an insight to the regulations.
Good Luck in your search.

 

[Guest]

many boats of the 60's and 70's had petrol engines .... Vire, Dolphin, Stuarts etc.
Boats even later had them ... and there are still Dolphins and Vires to be had recon'd / new .....

Many have changed over to diesel - cause it's safer than highly flammable petrol. Plus any petrol leak to bilge etc. will create petroleum vapours that will sit in the bilge until dispersed ..... Spark ignition engines in sail-boats were notoriously bad starters .... due to damp plugs / dynastarts etc.

Basically boat engines - especially sail-boats - are relied upon to start, run and perform without the care and attention lavished on them as with your family car !! Diesels fit the bill well.

As to choice ..... Inboard - I would prefer the diesel. Outboard - two stroke is generally lighter and more compact but more noise, 4 stroke is heavy and bulky but more economical and quiet .......
Both systems are good and have each distinct advantages. The petrol inboard is generally regarded nowadays to be weak contender !!

 

[oldharry]

[ QUOTE ]
Spark ignition engines in sail-boats were notoriously bad starters .... due to damp plugs / dynastarts etc.



[/ QUOTE ]

I never had any damp problems - even in some pretty damp old boats. Provided the plug leads and covers were in good order, and coils or magnetos were kept in good condition, then reliability was never an issue. Simply a matter of basic maintenance, without which any engine, whether diesel or petrol will become unreliable.

Reliability issues tended to centre round poor design or installation in my experience, as well as basically poor designs like the old Stuart Turner, some of which would simply not run properly from new - and have done much to add to the view that marine petrol engines are unreliable! If they really were, petrol powered cars would have disappeared from the roads long since, just as the British Motorcycle industry has.

 

[SlowlyButSurely]

I would say you have been lucky with your petrol engine. The issues you mention such as damp, lack of maintenance, poor installation etc are to be found on many boats. Add in some water in the fuel kindly supplied from the boatyard tank and you have a recipe for problems. The point is that a diesel engine will survive all these problems far better than a petrol engine and will keep going when the petrol engine would have packed up.

 

[oldharry]

[ QUOTE ]
a diesel engine will survive all these problems far better than a petrol engine and will keep going when the petrol engine would have packed up.

[/ QUOTE ]

Oh no it will not!!!!!

A spoonful or two of water in a petrol tank will cause problems, but many a time I have been able to keep a petrol engine running sufficiently to get out of trouble with water in the carb. SOn a lucky day, just revving it hard is enough to clear the problem.

The poor old diesel however cannot tolerate any water or dirt in its fuel whatsoever. A tea spoonful of water in the injector pump is enough to wreck it completely, and to cause mayhem with the injectors. The same with dirty fuel, if it gets past the filters for any reason. The entire injection system can be wrecked. Diesel fuel systems are far more vulnerable than petrol which is why they have to be protected so carefully with all those expensive filters! If a petrol engine does have a filter at all, (and it should!) it will be very basic and crude by comparison.

Neither engine will tolerate water being ingested via the air intake. Both will be instantly destroyed.

And read my post carefully! I never said I had not had problems with petrol engines - just that with regular preventitive routine maintenance, damp was not an issue. Anyone who has tried to run a recalcitrant Stuart Turner, or a Seagull outboard will know what I mean! And it is these two makes that have done so much to perpetuate the myth of the unreliability of marine petrol engines! And that in spite of the fact most outboards are not only petrol powered, but the majority are 2 strokes, which are notorious for their unreliability compared to their 4 stroke brothers! There are many very good reasons why you will never nowadays see a 2 stroke road engine except in the M/cycling fraternity who like getting their hands dirty, in spite of the higher performance attributes!

A neglected engine is a neglected engine whatever its fuel, and it will let you down sooner or later, whether it is in a boat, or a car.

Given a 'dead engine' situation at sea I would rate the chances of fixing a petrol engine far higher than that of a diesel.

 

[SlowlyButSurely]

Well, we'll just have to agree to differ then. I think ones perception of reliability depends on your own experience. As I said I think you have been lucky with your petrol engines. I have suffered several breakdowns at sea with petrol engines plus innumerable frustrating minor problems, but never had a problem with a diesel. I don't think many people would argue with diesel engines being more reliable.

Incidentally, I have had a Seagull for over twenty years and it's been very reliable.

 

[IzzyDeadyet]

Apologies for my late 'thankyou' for replying to this thread.

From your answers the boats in my price bracket are unlikely to have a diesel inboard.

That leaves petrol outboard or petrol inboard.

I'm going to take pasta_siimon''s advice to buy the boat I like regardless of engine (assuming I can find a boat I like - no luck so far)

and also dickh's advice to upgrade the fuel system if the boat has an inboard petrol engine.

You will notice that I've excluded 2 stroke outboards again. That's because I was put off 2 stroke engines for life in 1966. I seem to remember having to push my scooter home every time I rode it because I was incapable of judging the right mix when filling a half empty tank. After three weeks as a fledgling 'Mod' I flogged the scooter and bought a Honda motorbike.

I worry that I'll still get the mix wrong and pushing a boat home will be more difficult than pushing a scooter /forums/images/graemlins/smile.gif

Another dumb question. Say I find a less than 22 foot yacht with inboard petrol engine. Would it be safer not to use the inboard (leave it in situ as additional ballast) and just use an outboard?

And my final dumb question: If or when I come to sell will it be easier to sell a "small old yacht with outboard and redundant petrol inboard" than it would to sell "small old yacht with petrol inboard"?

Thanks

 

[oldharry]

Ok - but I must say I didnt feel I was 'lucky' at all when my petrol engine (a Stuart T) failed and refused to restart in the entrance to Portsmouth with Ark Royal bearing down on me!!!! fast maneovering and high speed tow from an MOD launch saved the day. Or the day I spent 5 hours in a flat calm trying to sail home with a recalcitrant Chrysler.

But then I felt much the same when my diesel went dead trying to get in to Aberystwyth in a SW6, and left me drifting on to the rocks at the entrance. Only saved boat and self because the jib was still hanked on, and could be hoisted -in record time, believe me! I can also remember trying to row a 24 foot heavy motor sailer in to Pwllheli, with a wrecked injector pump because a drop (literally) of water had somehow got past the filters.

I would still say on balance that a well maintained petrol engine is no less reliable than a diesel

In other words, if I have been lucky with my petrol engines, then you have been equally lucky with your diesels. But the vast majority of us use petrol engine cars quite happily, so basic reliabilty cannot be an issue, or we would all drive diesel cars?

What is at issue is that a poorly maintained petrol engine will go down much quicker than a diesel. But only if you leave maintenance to 'luck'

 

[ex-Gladys]

No comparison between 1966 Moped and modern outboard. Electronic ignition is the big one, plus modern 2 stroke oils and the Japs know how to make good engines. Outboards at 50:1 mix are tolerant - ours ran in as recommended at 25:1. Not a single oiling problem....