Need New Props On My 34' LRC

Took the props to the local shop. Was advised props were in bad shape, but fixable. They are now 23X23 3 blade. Took her out yesterday afternoon, 15 knt headwind 16 knt wot at 2400rpm, cruise confortable 12 knts at 2100rpms. Same rpms as before but 4 knts faster, bottom could be better, full water, 3/4 diesel.
Very happy with the results, but a friend got a pair of 23X23 4 blade that i will try. Report on that later.

Good to hear! I'll be very interested in learning the 4-blade results.

Do you see much change in your idle speed?

orvals said:

Took the props to the local shop. Was advised props were in bad shape, but fixable. They are now 23X23 3 blade. Took her out yesterday afternoon, 15 knt headwind 16 knt wot at 2400rpm, cruise confortable 12 knts at 2100rpms. Same rpms as before but 4 knts faster, bottom could be better, full water, 3/4 diesel.
Very happy with the results, but a friend got a pair of 23X23 4 blade that i will try. Report on that later.

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What is rated WOT on your 3208s? Seems that you are several 100 RPM short.

Fw, yes, there is. Big difference, now when I get into the Marina, I cannot keep it in gear, I would say at least 1 1/2 knot faster at 800 rpm.

Sc, WOT is 2800 rpm. I did notice that. I did all these runs with my mechanic, we will check on that, but with the original props that i got (23x21), wot stayed the same. But that was very underproped. Im getting the same wot rpm but with 2" more in pitch and 4 knts faster.
I get the WOT with clear exhaust, no smoke at all.

orvals said:

Fw, yes, there is. Big difference, now when I get into the Marina, I cannot keep it in gear, I would say at least 1 1/2 knot faster at 800 rpm.

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Three things:
-- it appears you have installed a bigger prop than you had previous
-- verify your RPM with a photo tach
-- what is your verified WOT out of gear

I don't know if it's the same as on my Perkins, but my high pressure fuel pumps are marked with the WOT RPM. Maybe you can look to see if your pumps are marked 2400 RPM.

Fixed props

These are the repitched 23x23...

I just ordered an optical Tach to check the ones installed, needed to do that anyways to make sure they are accurate, but yes, I do have 2" more pitch on them. Rated WOT on the 3208NA is 2800RPM, they get there easy at no load. However, running the 23x21 they reach 2400RPM, just as they do now with the 23x23, but running 4 knts faster. The botom is being cleaned as I write this, next test run on saturday. One thing I did change and forgot to mention, my engines had a ridiculously small air filter on them, I did all these runs without a filter on while I search for a bigger filter that will fit them.

Mine is not an exact duplicate of the 34LRC 3208 Cat powered boat of the OP. But after reading and holding my opinion to myself I think my experience might be applicable to a few readers here. I have a 34LRC with twin 200HP Perkins. Similar HP but somewhat lighter than the Cats. Up until late last year I had a pair of computer scanned 21x21 3 blades. They ran very well with a wot 0f 2450 rpm's at 23 MPH (statute). I was happy until I bumped the bottom on a couple occasions. The last one was rock. Who was it that said muddy Mississippi, they must have been in a different place). I ran across a pair of 21x19 4 blade Nibral props on Ebay for $900. I bought them and installed them just before haul out last fall. I reasoned that they might be under pitched but were close enough to be repitched if necessary over the winter. They looked tarnished but good when I bought them. After mounting them I could tell the difference immediately when I put the boat in gear pulling out from the yard. The boat moved right now when shifted. The props must have been reworked and not tweaked by the hard afterward, before I bought them. They were smooth, probably smoother than the 3 blades I had after they were rebuilt and scanned. WOT was the same 2450 RPM, but the speed increased about 1 MPH. At idle the boat is significantly faster. I have to keep it out of gear a lot more to maintain slow speed control. This is an advantage because if I shift to the opposite direction it stops right now. I suspect that the measured pitch has a bit of measurement tolerance. The 4 blades have more blade area and thus less slip compared to the three blades. This can explain the difference in speeds between the two. I couldn't be happier with the results, and this is made even sweeter with the cost.

Just came in from testing the props with a clean bottom.. Upwind, up to 18 knots at 2400rpm, moderate seas 4 to 6 ft waves 20 knots headwind. Did finally hit 20 knots, downwind and up to 2500 rpm. Very happy!!!
Cruise 14 knots at 2150rpm very confortable. Trim tabs not working, need them. Will try next week 23x22 4 blade.
Cats running at 185F no smoke whatsoever.

Cpr Craig... If I am not mistaken, you have a 1:1.53 transmissions, thus higher shaft rpms and smaller diameter. Glad to hear the improvement with the 4 blade, I am getting the same feedback here of better performance with the 4 bladed prop.

Finally got the 4 blade 23x22 props on. Not what expected, tops out at 15 knots, 3-5 seas 20 knots headwind. Lost top end. Feels with more "torque" while sailing upwind, waves do not stop the boat, plows into the seas better. I'll keep playing the lotto to see if i can get an extra $$$ and take them out again and put more pitch into them....

Ps.

My old 10 in garmin gps died.

Got the new Garmin 741xs with 18 radome....very nice!!!
Radar over chart is amazing, touch screen, wifi..the works on sale and rebates.

My old Furuno fishfinder recently died and I'm considering the Garmin 741XS. Pretty nice unit and the price is dropping. Still a lot for me to convert all over to Garmin, though. Would not change the Raymarine radar until it fails.

Sorry to hear the props did less than expected. It gets expensive playing with props.