TOPIC: OMC 21" Pitch 2-Blade Bronze Prop #384141

Does anyone have experience with the OMC 21" Pitch 2-Blade Bronze prop part #384141? I have a 87' Glastron/Carlson CVX-16 with a 1985 115 HP Johnson and have the best results with a 22" pitch Raker running 55.0 MPH at 5,400 RPM. Was wondering if the OMC bronze is worth tracking down and buying. Anyone have one for sale? Picture of my boat attached. Contract David at This email address is being protected from spambots. You need JavaScript enabled to view it.

I'd love to try this one myself David, unfortunately it's just not in the budget at this time;
www.boats.net/parts/detail/brp/B-0384140.html
LOVE that CVX, she's beautiful!

There are other 21" SST props out there. The stainless is heavy, but the bronze is even heavier - and thicker. A stainless wheel would give you better performance than going bronze.

Your RPM could stand to come up a bit. Those old crossflow V4s run best somewhere between 5500 and 6000 RPM. My 1983 Johnson 90 spins at 5800 with a light load.

- Scott

I called various prop people today and the conclusion is that the Raker is better than the 2-blade bronze OMC in that it has rake to lift the bow. The CVX-16 has a built in hook on the last 8" inches of the hull, on the pad, a straight angle going down, that keeps the bow in the water at speed. Even an extreme bow lift prop would not lift the bow high.

I have a 20" Raker that should give 400 RPM over the 22" Raker, meaning 5,800 to 5,900 RPM at 55 MPH. The redline is 5,500 RPM.

Only options now on props is a SRX 23" I will borrow next spring to try. It really is not an all around prop, just a prop for top speed.

Lifting the motor 1 to 2 notches on the transom will work, but I do not want to disturb something that is okay now.

I have tryed the 12 3/4 and 13 7/8 diameter stainless 21" OMC props (SST II's) and they are 1 1/2 MPH slower than the Raker.

I wonder if it would be possible to fill the hook and straighten it out. Might allow you to get the bow up a bit. Might also want to see if you can borrow some other brands of props to test.

5500 RPM is not so much a redline as it was the original max operating RPM. That was with 1980s fuel. It has been found since that the newer fuels don't burn as cleanly as they did in the 1980s and can leave deposits behind - called coking. If the engine is lugged, .ie wide open throttle is in the lower end of the original operating range (4500-5500 RPM) then this coking occurs. It accumulates in the ring grooves and contributes to "ring jacking" where the rings are pushed outwards by the build-up until they catch on the cylinder wall, port opening, etc. and break.

In talking with several OMC gurus over the years, they all have recommend that the crossflow V4s & V6s be propped to spin up a little beyond that original RPM range. Obviously, you don't want to be wringing them out at 7000 RPM, but approaching 6000 is perfectly fine. They build up less heat and run cleaner. Lugging them is akin to driving uphill, towing a trailer, in overdrive. It's that excess heat that contributes to the carbon/coke build-up.

On a side note, propping to reach 5700-5800 RPM does not mean you have to run it that fast all the time. The motor just has to have the capability of reaching it.

Chinewalker; Not meaning to hijack the thread, but. So, the older motors with the newer lubericants, and modern fuels, need to be propped to a higher rpm? I was shooting my '63 Johnnyrude 40 hp to 4500. Original specs said 4500 - 5000 should I prop for 4700? or closer to 5000. will be operated mainly at 75% throttle, max just to jet up on plane.

With the 22" Raker, I reach 5,450 RPM and do not leave it at full throttle very long. With passengers in the boat, I use a 20" Raker. I use Mercury Premium Plus oil at 45:1 with 93 octane fuel.

If this were my boat, I'd keep the Raker and lift the motor a notch and test. If the motor does not get to 5700 RPM, I would lift another notch. That Raker likes elevated heights, so I'd stick with it and try minimal setup changes to "chase the prop" until it hits its Happy Place. Once there, your face will hurt from all the grinning you'll be doing.

AZNative,
If your motor is rated at 4500-5000, then definitely aim for the 5000 plateau.
- Scott

I have one for sale.....OMC 2 blade bronze prop #384141 (13 3/4 x 21) cup. It's from my late father in law's estate.