Prop Size

SoundHead · Post by **SoundHead** » Wed Dec 15, 2010 10:29 am

I Have a 1986 10 Meter mid cabin. Crusader CH350 Engines. 1.5:1 transmissions. Props are old and we cannot see the markings to determine what the props are. However, based on the above can anyone supply the props size for the above that was speced for this boat? Thanks
Currently there are 3 blade props installed. 2500 she runs15 mph, 3000 she picke up to 18.5, 3500 is 19 to 20 and taht is it. The engines will spin up to 4500 or more but it seems to grabbing air. I do not get any more bit or speed. All is with a clean bottom. speeds via gps. With justa alittle growth on the bottom you can knock3 to 5 off all numbers. Engines appear strong,good compression and flow.
Anyone help?

RWS · Post by **RWS** » Wed Dec 15, 2010 12:17 pm

The mid cabin guys will chime in soon.

RWS

prowlersfish · Post by **prowlersfish** » Wed Dec 15, 2010 12:19 pm

A good prop shop can measure what you have .( if they can't you need a better shop) Good chance the OEM size prop will still be off as over the years our boats get heavier due to the stuff we add and bring aboard.

S.A.M. · Post by **S.A.M.** » Wed Dec 15, 2010 1:12 pm

The stock props were 17" diameter x 16" pitch. If your cruising speed at 3000 is 18.5 you're in the sweet spot.

What concerns me is 4500+ rpms. The midcabins were propped for a range of 4000 to 4200. After that your just burning fuel.

Prowlersfish is right about taking them to prop shop. I do think you have some issues that are showing up above 3500 rpms. The most you'll ever get if propped correctly on the top end is about 26mph @ 4000-4200 with the 350xls.

BobCT may chime in with his experiences.

Keep us informed.

SoundHead · Post by **SoundHead** » Wed Dec 15, 2010 2:34 pm

I am going to pull the props this weekend. Get them refurbed. I am giong to document as much as possible and will have the data avaliable Pre and post of the prop work.

BobCT · Post by **BobCT** » Thu Dec 16, 2010 4:57 pm

but it's an '88. Sherman and I went back and forth late summer as we were comparing the #'s with his 4 blade props. Yes, they are Nibral 17x16's 3 blades from the factory.

It seems like some of the mid cabin guys get in the 4,400 WOT range, I'm more like 4,100 myself.

"At 3,000 I was 15.2 knots on the GPS into a pretty good wind. 17.5MPH if I do the 1.15 conversion. WOT was around 4,100 at 22.5 knots, about a knot slower than last week"

That's from September.

I might upgrade to 4 blades myself. They are smoother and lift the stern a little and you do pick up some mid range speed. Plus, I wouldn't mind having an extra set of props on board.

Please let us know what you find out.

Bob

prowlersfish · Post by **prowlersfish** » Thu Dec 16, 2010 8:05 pm

And you could lose mid range speed and top speed . ( been there)

rossjo · Post by **rossjo** » Thu Dec 16, 2010 11:25 pm

Join http://BoatDiesel.com for $25/year. best prop calculator on the web.

RWS · Post by **RWS** » Fri Dec 17, 2010 5:13 am

I bought my 10 meter (not mid cabin based) from the ORIGINAL OWNER.

She wore 4 blade bronze props and has a pair of 3 blade nibrals new in th ebox onboard as spares, along with a spare shaft.

We ran both sets of props and the results as I recall were that we had a better top speed with the 3 blade nibrals, but more overall total efficiency with the 4 blade bronze.

Again my size, results and data will be different as I have a different shaft angle, diameter/pitch and gear ratio than the mid cabin based hulls.

RWS

Trojan Boat Forum

Prop Size

Prop Size

Thanks for the response!

I have basically the same boat