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Old 28-03-2011, 19:13   #16
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Re: small slow diesel?

Just to give you an idea about slow turning diesels, my 1978 Perkins 4.236 puts out about 62 HP and I cruise it at 1200-1500 rpm. 1200 gives me about 6 knots in calm conditions. The engine has tremendous torque and swings a big three-bladed prop.
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Old 28-03-2011, 21:14   #17
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Re: small slow diesel?

k. i am the WORST when it comes to electrical. my knowledge of electrical is ZERO last time i tryed i zapped the hell out of myself.

what does 115 A mean? my guess is it puts out 115 amps? and that charges the batteries?
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Old 28-03-2011, 21:26   #18
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Re: small slow diesel?

There are some nice things about the slow rev rate --

A pal of ours was restoring his father's old motor sailor which was powered by a beautiful Gardner 4 cylinder forty-odd HP engine. He called the factory for info on what should be redone to restore to new condition. They asked "how many hours", and were told 12,500... response? "Nothing to be done... hardly broken in yet"

It was red-lined at 900 RPM.

Try that question on your local Yanmar dealer!

Cheers,

Jim and Ann s/v Insatiable II lying Church Point, NSW, Oz
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Old 29-03-2011, 08:00   #19
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Re: small slow diesel?

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Originally Posted by tomales bay View Post
k. i am the WORST when it comes to electrical. my knowledge of electrical is ZERO last time i tryed i zapped the hell out of myself.

what does 115 A mean? my guess is it puts out 115 amps? and that charges the batteries?
12 Volt systems are very simple and you will quickly learn whatever you need from any book or just by browsing the web.

115 A is a 115 Amp alternator, 12 Volt (actually the 12 is nominal as the alternator delivers about 14.4 Volt on terminals).

Try to avoid zapping things as some (especially around the starter motor and around batteries may not only hurt you but also start a fire).

Fuse things and read up!

b.
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Old 29-03-2011, 08:45   #20
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Re: small slow diesel?

The days of the old slow turners has past, as most engines now are adapted from land based units it seems.
My old Coventry Victor used all its HP to turn a massive flywheel, anything attached to that flywheel, just went along for the ride
Oh!!-it was hand start, and never failed to idle when the decompression lever was released.
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Old 29-03-2011, 08:49   #21
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Re: small slow diesel?

Jim,

Worked on a Straight 8 Gardner that was in its 5th hull. Owner had all the logs on the engine.
Said it was a youngster built in 1946 IIRC. Engineering masterpiece
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Old 29-03-2011, 09:07   #22
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Re: small slow diesel?

The third world is awash with small diesels with rat tail props for little boats. They run about $1000. They hand start with a crank on the flywheel and can be hooked up to just about anything. The fuel tank is usually a plastic jug with a rubber hose.
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Old 29-03-2011, 11:19   #23
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Re: small slow diesel?

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Originally Posted by lorenzo b View Post
The third world is awash with small diesels with rat tail props for little boats. They run about $1000. They hand start with a crank on the flywheel and can be hooked up to just about anything. The fuel tank is usually a plastic jug with a rubber hose.
And the radiator is an open top tank that boils water to cool, just keep adding water, no water pump, They make them up to 26HP that I know about.
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Old 22-01-2013, 16:33   #24
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Re: small slow diesel?

RPM and life of engine are not necessarely connected, a long stroke, slow turning engine can have as much wear as a high rpm short stroke engine. its the piston speed that matters among many things. for the same rpm a piston with a 6" stroke has to travel 3 times as fast as one with a 2" stroke for the same rpm. , and when its time to change direction the stresses on mechanical parts are much greater on a long stroke engine... so, a 1500 rpm engine might last less than a 3000 rpm engine..
no one mentionned kubota diesels. the V2203, 48 hp at 2800 rpm will easily last 20,000 hrs, they are used in reefer units for semi trucks, carrier corporation recommends oil change intervals of 2000 hrs with normal oil and 4000 hrs with synthetics. recommended rebuild is 20,000 hrs, they run their engines at 1600 rpm, about 3o hp. beta marine and nanni both use that engine. kubota also makes many smaller diesels, i have a gen set with a small 3 cylinder kubota that has 12,000 hrs. oversize the engine, run it at a lower rpm closer to the torque curve and it will last forever and get better fuel efficiency. dont prop it for max rpm, prop it to be matching its load or about 75% .. years ago i had a 75ft schooner, 84,000lbs , it had a ford 120 diesel i spun a 29" prop , at 1400 rpm i would get 1.4 gph at 6 knots 24 hrs a day. theres great diesels today, 30 years ago we serviced Whitte diesels on remote farms, slow turning and heavy, single and twins, they ran 24hrs a day for 3 years, we didnt even shut them off to change oil, pulled the drain plug let it drain and refill.....the little 2cylinder 21 hp diesel i removed from my boat weight over 500 lbs, my new 48 hp weights 500 lbs and is smoother and doesnt vibrate the boat... progress can be a good thing.
eric
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Old 12-02-2013, 21:11   #25
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Re: small slow diesel?

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Originally Posted by tomales bay View Post
hello guys and gals.

i see several threads about diesels for bigger boats but what about 25-30ft? i dont see many small diesels that are slow. reading threads most of the threads say you need a slow diesel to get the best GPh. but i dont see many small diesels that are slow. the small yanmars turn around 3600rpm or something like that. what is considered a slow rpm for a cruising diesel? i know you don't normally use the engine at its peak of 3600rpm but isnt that to high of a max RPM for cruising? i was looking at the smallest of the lugger line and have heard nothing of good praise about lugger (northern lights) but i was looking for more of around 30hp and lugger is 40hp. i see volvo pentas have smaller engines and they turn around 3200max rpm and i see a lot of people with volvos.

when looking at cruising engines. you need the hp required to move your boat properly at the cruising rpm you cruise right? not the max engine hp and then you cruise at a lower rpm resulting in a lower hp?

so my questions are
what is a good max rpm for a small cruising diesel
what are good brands

and what ever you want to add to this.

thanks
John
Its all a matter of engine cubic inches. A larger engine will turn fewer rpms than a small engine to make the same speed. When a 3l engine is turning 3000rpm for 7knts in the same boats a 6l engine will turn 1500 to make the same 7knts. In a nut shell, you don't get something for nothing it is all paid for in hp or work. Now keep in mind the screamer at 3000 rpm is not going to last as long as the 6L at 1500. The 6L will have lots of reserve torq for head seas while the little guy will be straining big time
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Old 13-02-2013, 06:21   #26
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Re: small slow diesel?

I snagged a Westerbeke 64A to replace the old Ford Lehman 80 in Dionysos when I repowered her. 2300 rated RPM, naturally aspirated. 64 horsepower. She's a de-rated 80 horse engine, and runs like a top. They might make the same kind of engine in smaller sizes but I don't know.
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Old 13-02-2013, 08:27   #27
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Re: small slow diesel?

A small dependable deisel that gave me great service was an 18HP Farryman that had the advantage of hand starting as well as electric start. The single banger was also easily rebuilt with a replaceable cylinder available. Raw water cooled and started easily.
Another alternative which was the benchmark engine in old west coast trollers and gillnetters was the Easthope engine that started with throwing a flywheel by hand. Had a decompression switch that allowed you to spin the flywheel by hand then kick in the compression. It was also a single banger and high grades for dependability. The familiar 'thump thump' sound was almost a welcoming sound as one of these old buggers went by you. Very lean on fuel and easy to repair. Not sure you are able to find them anymore but vintage fishboat communties like Steveston, BC at the mouth of the Fraser River would be a good place to start. The Easthopes were direct drive as I recall with no transmission, only a clutch system so less things to go wrong. I do miss those days and driving those old boats around the PNW... cheers, Phil
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