I must have wrong prop for F-25, grateful for suggestions.

wet wonder · Post by **wet wonder** » Thu Apr 30, 2009 11:02 pm

Just to interject into the prop debate for a moment - I have a diver coming tomorrow to swap out the present prop for the 13R10. He's charging $200. I generally do everything myself, but I don't have the prop puller and the water is still pretty cold up here. So I'm making an exception by hiring out on this one.

gjrylands · Post by **gjrylands** » Fri May 01, 2009 12:09 am

wet wonder wrote:Just to interject into the prop debate for a moment - I have a diver coming tomorrow to swap out the present prop for the 13R10. He's charging $200. I generally do everything myself, but I don't have the prop puller and the water is still pretty cold up here. So I'm making an exception by hiring out on this one.

Let us know what size the original prop was and if the new prop runs any better.

prowlersfish · Post by **prowlersfish** » Fri May 01, 2009 6:43 am

gjrylands wrote:
wet wonder wrote:Just to interject into the prop debate for a moment - I have a diver coming tomorrow to swap out the present prop for the 13R10. He's charging $200. I generally do everything myself, but I don't have the prop puller and the water is still pretty cold up here. So I'm making an exception by hiring out on this one.
Let us know what size the original prop was and if the new prop runs any better.

please do for 200 bucks i hope he is going to clean the bottom also . with out a clean bottom /shaft rudder you can't tell if the props right or not .

Have the diver check and make sure both props are R hand as your new one is right hand .

good luck

gjrylands · Post by **gjrylands** » Fri May 01, 2009 9:15 am

prowlersfish wrote:
gjrylands wrote:
wet wonder wrote:Just to interject into the prop debate for a moment - I have a diver coming tomorrow to swap out the present prop for the 13R10. He's charging $200. I generally do everything myself, but I don't have the prop puller and the water is still pretty cold up here. So I'm making an exception by hiring out on this one.
Let us know what size the original prop was and if the new prop runs any better.

please do for 200 bucks i hope he is going to clean the bottom also . with out a clean bottom /shaft rudder you can't tell if the props right or not .

Have the diver check and make sure both props are R hand as your new one is right hand .

good luck

That would be a hoot if they were different.

wet wonder · Post by **wet wonder** » Fri May 01, 2009 4:14 pm

The diver put on the 13x10 today. I took the boat out, despite rain, 10-15knot winds and two foot breaks. I was able to get it to 3,700rpm. So it's doing 700rpm, or about a 25% rpm increase. Seems like a good start.

prowlersfish · Post by **prowlersfish** » Fri May 01, 2009 5:20 pm

great ! Did you pick up any speed ? do you know if your tach is correct ?

wet wonder · Post by **wet wonder** » Fri May 01, 2009 5:39 pm

The water was very rough today, and the wind and tide very strong. It wasn't good conditions.

When I went with the wind at my back, I was going cross current and breaks and started to lose control at 15 knots before having to slow down.

Then I turned with the current but into a very strong head wind got it up to 14 knots at 3500 rpms.

My feel is that It'll do 20+ now on some calmer water, but I guess it's hard to be sure until the weather lets up. There's a pretty big system coming up the East Coast and we'll be in it here for the next four or five days. So first good day I'll try again.

As best I can tell, the old prop was a 14x10 cupped. Definitely larger diameter than the 13x10 b/c it wouldn't fit in the same box. So it seems like I'm going in the right direction.

Thanks everyone for your help. Looking forward to the rendevous.

wet wonder · Post by **wet wonder** » Fri May 01, 2009 5:39 pm

How do you verify the tach?

gjrylands · Post by **gjrylands** » Fri May 01, 2009 8:40 pm

With another tach. A Snap-on timing light has a tach built into it. Others may also.

Maybe Paul can give you a better idea how to varify the tach.

prowlersfish · Post by **prowlersfish** » Fri May 01, 2009 9:26 pm

Photo or laser tach , To me its a must have tool shop a round they very in price . here's a cheap one I can't rember where I got mine but this one should be fine

http://www.meter-depot.com/tacho.html

heres what I have (I would buy the laser )
http://www.circuitspecialists.com/searc ... tachometer

you can even cheak shaft speed to see what gear raito you have

wet wonder · Post by **wet wonder** » Sat May 02, 2009 2:02 am

A device that costs less than $200. That's encouraging. I'll do just that.

wet wonder · Post by **wet wonder** » Sat May 02, 2009 2:02 am

How 'bout checking the timing. Any tips?

necsteve · Post by **necsteve** » Fri May 22, 2009 7:02 pm

I have an F25 here in the northern part of the Chesapeake.Its a 1976 with a 318 that I have had since 1990. I have had a fuel flow meter since 1992. I just had to respond to give you my info.
My most efficient cruise speed is 17-19 knots (confirmed with loran and gps)
My fuel flow at that speed is 7 to 7.5 gph . My top speed has been as high as 27 .knots at 3700 peak rpm. My carb is a replacement 4 barrel that I rarely open WOT. My prop is a cupped Michigan wheel ,slightly higher pitched,slightly larger than the original 14x10 3blade.Performance was reduced,(including speed to plane) with the new prop...but economy improved. To maintain a given speed,engine rpm was reduced about 200-250 rpm.There are definately two most important factors in fuel economy...how much power it takes to move the boat thru that water AND most forgotten, is how much energy is consumed moving all those gasses thru the engine.To a point.. reducing rpm is good.I suspect you passed that point With a lot of fine tuning,I have manged to improve my fuel economy 10-15 percent but in doing so,i must keep the boat properly loaded with enough weight toward the bow. Either your engine is not capable of bringing up the rpm due to a tuning issue..or you have too much prop....or both.

On one of your posts,(this one ???) you asked about timing the engine.I have tried doing the old timing lite routine. That was good as a starting point only (318 chrysler). I "power tune" the timing underway with great success. You have to know what to listen for tho.

2 blade,3 blade,or 4 blade I dont want to get into that...you have to get the engine into the preferred operating range first

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I must have wrong prop for F-25, grateful for suggestions.

F25....props