Spare Props

Chris Anderson · Post by **Chris Anderson** » Thu Sep 21, 2006 4:54 am

I have a set of brand new props (still in the box) to sell. They were spares for my Gas engines before converting to diesel. They are General Propeller 20X19 with a bore of 1.375. I'd like to get $500 for the pair. I'll bring them to the Bertram Pride event if anyone is interested and going to Tween Waters.

photo finish · Post by **photo finish** » Thu Sep 21, 2006 5:15 am

3 blade or 4 blade, bronze or nibral Those are a perfect fit for my boat , however I already have a spare set.I hope someone else can use them.

Chris Anderson · Post by **Chris Anderson** » Fri Sep 22, 2006 6:17 am

They are 3 bladed Bronze.....opps sorry I forgot those details.

BottomLine · Post by **BottomLine** » Fri Sep 22, 2006 8:34 am

Chris: What brand/model are they e.g. Federal Equipoise? Mike Ford

Chris Anderson · Post by **Chris Anderson** » Wed Sep 27, 2006 5:26 am

Hi Mike, I'm going to try to post a image (1st attempt). I think the props were made by Federated/Michigan Wheel as they say "FED/MI" on them.

Gonzalo · Post by **Gonzalo** » Wed Nov 05, 2008 11:06 am

Chris, I bought an 89 converted to diesel with twin Cummins (6BTA). Would like to know if I have the right props, can you give me details of what you put in yours? Thanks

IRGuy · Post by **IRGuy** » Wed Nov 05, 2008 12:00 pm

Gonzalo... You need to provide more info on your engines before anyone can tell which props might be best.. What is the rated HP of your engines, and what is the transmission ratio you have? Several of us have the Cummins 6BT engines in the 315-330 configuration, and some have the 6BTs in the 370 HP setup. If you have the 315-330 HP engines, and a 1.5 to 1 transmission ratio you will be in very good shape with the same props as I have, namely 3 blade 21" diameter by 23" pitch, no cup. If your transmission ratio is in the 1.75 to 1 range (meaning your output prop shaft turns slower at the same engine speed than the 1.5 to 1 transmission) you could use a larger diameter or larger pitch wheel, or combinations thereof. The props which Chris refers to above sound as if they would be better for a gas engined boat with perhaps 350 HP. Gas engines typically rev at higher speeds than diesel, ie: diesels have more torque and develop their max HP at slower speeds than gas. How do you know if you are using the proper combination of prop diameter and pitch? Take your boat out on a calm day in it's NORMALLY LOADED condition, and push the throttles all the way forward to allow the engines to run as fast as they can go. They should be able to turn between 150 and 200 RPM faster than their rated speed. Again, with my engines, which are rated for max operating speed of 2,800 RPM, I can get 2,950 to 3,000 RPMs. Don't operate with these throttle settings for any longer than it takes to get up to maximum speed. If your engine can't reach the speed which is at least 150 RPM higher than it's rated speed it is "overpropped", meaning it is working too hard because your props have either too much pitch or are too large in diameter, or a combination of the two. Diesel engines like to work hard, but they do not like to be overstressed by running props that are too agressive. If you think that your engines could run faster than 200 RPM faster than their rated speed they are "underpropped" and are not being asked to operate at their optimum performance level. This is not necessarily a bad thing, but your engines are expensive and you might want to use more agressive props to increase your boat speed and get all the performance you paid for, and the engines are capable of delivering, while still being within the manufacturer's design parameters. Normally, your cruising engine speed should be at least 200 RPM less than rated speed. With my transmission and props my boat runs at just a little less than 1 knot per 100 RPM.. meaning that at 800 RPM I can get about 8 knots, at 1,200 ROM I get almost 12 knots, and at 2,700 RPM I can get about 26.5 knots. To be safe I make it a point to consider my max engine speed to be about 400 RPM less than rated speed of 2,800 RPM. This should result in less stress on the engines, which translates into longer life.. which translates into $$$$$$$!

otf · Post by **otf** » Fri Nov 07, 2008 3:31 am

I sent a PM, might be interested in the props. Currently running 350 crusaders.

Post by **dougl33** » Fri Nov 07, 2008 7:08 am

Scott, The PM function doesn't really work very well (or at all). It's not a PM in the usual sense. When it does work its supposed to send an email directly to the person you're trying to get in touch with. Chris doesn't post here very much, so don't be surprised (or take it personally!) if he doesn't get back to you.

otf · Post by **otf** » Fri Nov 07, 2008 3:18 pm

I have caught on theat the PM doesn't work, I wonder why. Anyway, maybe someone reading this has his email and can alert him.