Speed under power

[georgevest]

I have followed with much interest the various messages re cavitation, and expect that some of you might be able to help me with a slightly different prop problem.

I recently bought my 350 from the original owner with a 15" Max Prop already installed. According to the previous owner, the pitch was adjusted to 18 degrees shortly after the installation. The boat seems to handle well in forward and reverse.

My problem, however, is speed. With a clean bottom and a clean prop, I am getting only six knots (at best) in smooth water with no wind at 2500 rpm. Although I've not carefully calibrated the knotmeter as yet, the slow speed is closely confirmed by the GPS in conditions with no appreciable current.

I would like your input on what speed some of you are getting. Perhaps my expectations are too high but with a 31+ foot waterline and a hull speed of 7.5 per the owners manual or 7.3 per my calculation, I would expect more.

I still have the original 15 x 9 three blade fixed prop and will be watching with interest the reports re cavitation and other prop options.

Thanks for any help you can provide.

George Vest

[Whitehook]

I mentioned the following in a post on the old sailnet board but I thought I would post this again. There has been much discussion about the PSS shaft seal and cavitation noise so I thought that I would ask Jerry Douglass about it during the last Catalina East Coast Rendezvous.

As I recall and despite what has been assumed by a number of members the water injection was added at the factory after about hull #200 to guarantee good water lubrication of the cutlass bearing and not to eliminate the temporary cavitation type of noise that is sometimes heard upon hard engine acceleration or in heavy seas. This cavitation type of noise is not constant and only some boats have this noise. It does not seem to be based on whether or not they are equipped with the water injection and it is not considered to be serious. As we now know it appears to be caused by the prop.

On the other hand, improper shaft lubrication could manifest itself as a constant vibration as the cutlass bearing starts to overheat and wear. Unfortunately, by the time you feel or hear a constant vibration the damage has already started if the vibration is a result of the dry cutlass bearing.

A retrofit kit was sent to everyone without the factory installed water injector and it is the position of PSS and of Catalina that it should be installed on all C350s.

If it has not yet been installed then the owner should make sure that the seal is “burpedâ€

[Tim April IV]

George - we are able to routinely cruise (i.e. 2300-2400 rpm) long distances at around 6.1 or 6.2 knots, and approach or exceed 7 knots at 2600-2800 rpm.

Of course, under sail, we frequently are able to exceed 7 knots. I've even seen 11 knots once for a short period of time.

We have the factory installed (on the earlier C350's) two blade prop.

Good Luck!

Tim Brogan
April IV C350 #68
Seattle

[Copacetic]

George,
I agree with Tim as to the RPMs and speed, although I have the upgraded three blade prop. Punch it up to 2800rpm and you should be pretty near 7 knots more or less, depending on variables.
I've also seen the "surfing" speeds, hitting a 9 on a downward swell.

[wmwel@mindspring.com]

We have never approached the kind of motoring speeds referred to by Tim and "Copacetic." Our 350 (Hull 142) chugs along at 5.5 or so at 2400 rpms. We can goose up the throttle for short term situations but I can't imagine doing that for a long haul. I'm now wondering if our long trip from here to the Dry Tortugas last Spring might not have needed to take so long! Good luck.

Bill Welsch
Punta Gorda, FL

[Triumph]

I'm the owner that has been testing props for Catalina in an effort to solve the cavitation - vibration issus.

The three bladed prop supplied by Catalina give me 6.4 knots at 2400 rpm. Flats seas, and a little fuzz on the hull. 2800 rpm yield 6.9 knots. 2000 rpm gives 5.5 knots. Hope this helps.

[Jack McDonald]

George,
I've had my Max Prop for a couple of seasons. I have the 15 inch 3 blade Max Prop. I've tried it at two different pitches. From memory (all bets are off!) I will try to tell my experiences.

18 degrees pitch:
2400 rpm gives about 6.0 - 6.3 knots speed (medium seas)
2700 rpm gives about 6.5 knots speed
no black smoke from exhaust
incredible reverse power
good reverse control

20 degrees pitch:
2400 rpm gives about 6.7 - 6.9 knots speed (medium seas)
2700 gives about 7.1 knots speed
lots of black smoke from exhaust, leaves black marks on hull
incredible reverse power
good reverse control

I went back to 18 degree pitch because of the black smoke.