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Old 10-11-2013, 10:55   #31
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Re: Islander 28 Refit (propellor)

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For continuous operation, in general an engine has to run at 80% of maximum power for long life.
This is standard for most commercial operators and I would recommend it for recreational boats as well. To get there you need to pitch the propeller to pull 80% of maximum power at full rpm. That puts the propeller demand curve well below the power curve and means using less pitch than is typical. Limiting the engine rpm by over-pitching the propeller is perhaps the worst thing you can do to an engine. I'm sure Dave Gerr would agree.
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Old 10-11-2013, 17:52   #32
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Re: Islander 28 Refit (propellor)

Dave Gerr does say that a propeller pitched so that maximum RPM is 90% of peak horsepower is OK. This means that a RPM of 3240 is acceptable on the Yanmar. However, looking at the horsepower curve, at that RPM with a propeller taking all of the horsepower at that pitch, 17 horsepower is taken by the propeller. If we take 80 percent of the maximum of 18 horsepower, this is about 14.4 horsepower, so would have to drop the RPM about another 200 RPM to 3040 to achieve long life for this engine at 80% power and this higher pitch.
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Old 05-03-2014, 14:38   #33
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Re: Islander 28 Refit (propellor)

In case anyone still gives a rip.....

I had a couple of prop suppliers spec a prop, then found one on ebay and had it repitched and balanced.

So technically I am under clearance as there is only about 1.5" to the hull. But there isn't much hull there as it is the stem of the wineglass shape.

I also underpitched based on Garr and what I read on this thread. The engine is governed and I care less about speed than I do about engine life.

I am spinning a 13x10. As we just waddled across the harbor from the lift to the slip, all I really know is that it doesn't make lots of hull noise, and not much prop walk. Still have some bugs to work out to get the engine to rev (even in neutral) When that's done I'll report on the sea trial. Thanks to all!
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Old 06-03-2014, 12:23   #34
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Re: Islander 28 Refit (propellor)

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...Still have some bugs to work out to get the engine to rev (even in neutral) When that's done I'll report on the sea trial. Thanks to all!
Stale diesel might be the engine rev problem. Modern diesel is refined from heavier distillates by catalytic conversion just as gasoline is. Both of these fuels now have a much shorter storage life. Here is a very technical article about all forms of diesel fuel intended for marine use, but just reading through it without taking notes on definitions gives a good idea of modern diesel fuel problems. My recommendation is to pump and clean the fuel tank.

http://www.chevronmarineproducts.com...1a_DESKTOP.pdf
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Old 09-03-2014, 18:41   #35
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Re: Islander 28 Refit (propellor)

Well $600 later the tank is drained and cleaned. Still need to replace the electric pump so for now she runs out of jerry can full of fresh fuel. Still won't rev beyond an estimated 1500 rpm. Also need to fix the tach. Duh.
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Old 10-03-2014, 10:23   #36
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Re: Islander 28 Refit (propellor)

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Well $600 later the tank is drained and cleaned. Still need to replace the electric pump so for now she runs out of jerry can full of fresh fuel. Still won't rev beyond an estimated 1500 rpm. Also need to fix the tach. Duh.
Was there much sludge in the fuel tank?

Three products to use to prevent future diesel problems: diesel biocide added on fuel up to prevent micro organisms from growing in the fuel tank when water is present (be careful, poisonous), fuel stabilizer added with each tank fill or once a year to stored diesel, and a Baja filter to get the water and dirt out while taking on fuel. Also make sure you have plenty of spin on fuel filters, or maybe a Racor filter with a glass bowl and filters. Google Baja filter and lots of comments show up on cruisersforum dot com

You might have plugged fuel filters that keep the engine from running above 1500 RPM. The next step is bleeding the fuel injection system for air bubbles if filters are alright. Are you getting any black smoke after warmup at less than full power setting? Any white smoke with strong odor of raw diesel or raw diesel on the water from exhaust? Any smoke at all?
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Old 24-03-2014, 02:15   #37
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Re: Islander 28 Refit (propellor)

Good news is that after a little run time she starts revs and pushes just fine. A few seconds of white smoke on cold start then clean. It is running out of a jerry can right now. Paid some serious dough to get the tank pumped and cleaned. Bought a racor with water separator and a new electric pump which I will install sometime soon.
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Old 24-03-2014, 15:55   #38
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Re: Islander 28 Refit (propellor)

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Good news is that after a little run time she starts revs and pushes just fine. A few seconds of white smoke on cold start then clean. It is running out of a jerry can right now. Paid some serious dough to get the tank pumped and cleaned. Bought a racor with water separator and a new electric pump which I will install sometime soon.
Problem solved, a little white smoke on startup is alright. You do not want this fuel degradation to happen again. Bad fuel is what stops an engine 80% of the time, or at least that is the number that keeps coming up from time to time on CF. If the tank was not steam cleaned, just flushed out, I would use biocide to kill anything left. The fuel stabilizer is not needed unless you are going to leave the diesel in the tank for many months. The hotter the climate the more you are likely to need the stabilizer. The most important thing is to keep water out of the diesel, but you never know who might give you a tank full of fuel containing water.

The safest way is to filter all fuel through a Baja filter. Another way is to take the new fuel pump and filter and use it to polish the fuel. Run a fuel line to the lowest part of the fuel tank and use the fuel pump to circulate diesel from the bottom of the tank where the water will collect through the new filter and back into the tank. If there is water in the fuel, you will see the water in the bottom of the glass bowl on the filter. This setup is for fuel polishing. If you did get water in your diesel from a storage tank, most likely there is biological growth in that diesel which will plug up the filter again. So, if there is water in the filter bowl after polishing, put some biocide in the diesel tank.
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Old 24-03-2014, 16:51   #39
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Re: Islander 28 Refit (propellor)

Of course if your fuel and tank are spotless and you don't need biocide and you add it, it hurts nothing, just like the stabalizer, if it's there it hurts nothing.
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