Getting Prop Work Done...

[Jackman]

Just curious,

I just dropped off my new props (from the repower) to have them prop scanned to class 1 and make sure they are what I think they are as far as pitch ect. I did not have this done before I used them for the repower because they were new out of the michigan box when I got them. I figured that I'd try them, see what performance I got and then get them tuned to class 1.

Anyhow, I'm probably just poaranoid but what do you guys do to make sure you get your props back and not someone elses? I personally can't visually tell the difference between nibral and bronze...especially when they are all cleaned up.

By the way, I expected to use 21x21x4-blade props to get about a 2900 rpm WOT. These props according to the seller (marina) were 21x23x4-blade. I expected 2900rpms because a Hatteras identical to mine was done by Tony Athens a couple of years ago. I don't have a diesel genny in the lazarette like that guy did and I have a clean bottom with trim tabs. I don't know if thats enough to make a difference or not. The engines don't seem overloaded. Never have overheated and no black smoke.

 

[SeaEric]

I'm probably just paranoid but what do you guys do to make sure you get your props back and not someone elses? I personally can't visually tell the difference between nibral and bronze...especially when they are all cleaned up.

I have wondered about this myself. I think you have to have some confidence in the Prop Shop that you send them to. I have had a good experience with Black Dog Props on Kent Island. They have all the fancy scan equipment. I had them do my props 2 years ago and was very pleased with the resulting (minor) increase in performance.

If a shop was going to screw with you by intentionally switching out your rightful property, I think that behavior would catch up to them rapidly.

In this day and age, bad news travels way faster than good news.

 

[thoward]

We had ours done with Propscan. Stuart prop did a nice job but was not shy about his prices. The props should have serial #s.....

 

[Brian Degulis]

I don't think I would worry about that but if you are just get a letter or # punch and distort it with a grinder you will make a mark that couldn't be duplicated. Punch each prop at the bottom of the keyway.

Brian

 

[dougl33]

Jackman,

What were you getting for RPMS last summer? You are running 1.5:1's with 6BTA's correct?

 

[Jackman]

Yeah. New mechanical 330b's with 1.5:1 trannies.

I was getting 2850 WOT only with the tabs and made 31 to 33kts. Without the tabs the bow was high and she did not make the 2800 minimum. That was with what I thought was 21x23x4bladers. Cruise was 21 to 23kts at 2200rpms.

I just got called from the prop scan shop and they said after the scan they found the port prop to be 21x 22.6 with #4 cup but not consistently #4 on all 4 blades. The stbd prop was 21x22.8 with #4 not consistent on all 4 blades. That could explain the couple degrees increase in operating temperature between the port and stbd engines. Not much but a small difference is noticable. After we discussed the scan we decided to make both props match at 21x22.6 with a consistent #4cup and some tip cup because of my prop pockets. He said this should add 50 to 100rpms.
We'll see what happens. I just know I don't need to go any faster! Anyone ever hear a hatteras owner say that? Probably not.

 

[dougl33]

I re-powered last spring with 300hp RTO 6BTA's (cpl 0970). I am running 21x22 3 blades with a med cup (not sure what number that translates to) and 1.5:1 220a's. At WOT I was getting 2900rpms on the starbord but only 2860rpms on the port (photo tach). Trim tabs do not seem to have any affect on WOT rpms or speed on the Bert. In fact, over 20 knots the tabs have very little affect at all other than to help balance an un-even load. WOT speed is 28-29 knots. Cruise is 22-23 knots @ 2450 rpms. I had both props looked at again this winter and the pitch on the port prop was a little more than 22. They (Haskell and Hall) corrected the pitch.

Hopefully this will be enough to pick up the 40 missing rpms I'm looking for.

Ditto on your smoking and over-heating comments. I love these engines.

I had considered picking up a set of 4 blades this winter. From talking to the Acu-tech guys at the boat show it seems that the best bet with 4 blades is to drop down to a 20 inch diameter and go up in pitch to around 23-24, that way you'd still get the rpms without loosing the speed. They're also recommending a prop with more blade area than Mich DQX's. They were recommeding ZF's at $1440 a prop. Unfortuantely, $2900 is too much for me to spend on fine tuning. As one of the guys on the Bertram 31 site likes to say:

"The enemy of good is better."