Props - recommendations from the techs

[mstailey]

I've recently added digital tachs (Aetna) and after checking with a photo tach I feel comfortable with the accuracy.

Running the boat today to where it's being pulled out for winter I ran WOT for 5 minutes. Per CPL (vt903-M1 Cummins) max rpm is 2800.

Results:
Starboard = 2815
Port = 2793

I did verify throttles operate injector pump at max travel on both engines.

Temps were 185 - 187 and during WOT no smoke coming out the exhaust.

Traveling down wind of wind speeds @ 6-10 MPH. Air temp was 49 deg. Water surface was pretty much flat.

The boat had 100 gals of fuel in each tank, no fresh water and just me on the boat. I do not have a lot of extra equipment but do not know the weight of the boat at this time, however. I should get that tomorrow when she comes up in the slings.

The delivery sheet from Hatteras showed a 24x27 4 blade wheel. What is currently on there is 24x26. I've only confirmed this by the numbers stamped on the wheels and have yet to have a prop shop confirm actual figures.

Based on not having full fuel - water tanks or bodies aboard I'm thinking of talking with the prop guy and having him remove .5 - 1 inch of pitch. In otherwords if he verifies that the wheels in fact have 26 in pitch go down to to 25.5 - 25 in of pitch.

Rule is pitch down RPM's up - Correct?

What do you think?

Thanks.

 

[Jaxfishgyd]

Mike,
What motors do you have ? In my 43', I have 6-71 N's and both Detroit and Hatteras told me my WOT should be 2450 rpm.

 

[mstailey]

Charlie,
Cummins VT903-M1

 

[Jaxfishgyd]

Never mind, see you have Cummins........ Damn bifocals must be the reason I missed that when I first read your post...
Heck, it was only 89 here today so I know winter is coming due to the fact it's under 95 now......

 

[Paul45c]

Rule is pitch down RPM's up - Correct?

What do you think?

Thanks.

Yes, pitch down = higher rpms. On my 45c with 4-blade Michigans, I'm roughly 26x26, if I remember right. I'd have to check some notes. But anyway, I think 1" of pitch taken out got me about 100 rpms.

 

[jim rosenthal]

I would take out no more than 1", and see where you are. You are at the end of the season with a bottom that is probably not perfectly clean. You might also take a look at the bottom once she's dried out to see what you can do to minimize drag; every little bit helps some. I think you are on the right track.

 

[34Hatt]

I agree no more then 1" probally .5 but you won't know until they scan them. I went thru this and prop scan found 1" variation between blades and that was on a 3 blade wheel . Wheels were done 1-2 years pior and didn't even have a ding in them. So that is why I only go to a Prop scan shop now

 

[Passages]

As a point of reference, 2 years ago I took 2.5" out my 24" 3 blade props.

WOT RPM increased 16o.

 

[mstailey]

Thanks guys.

Jim,
Good point. I did look at the bottom today when they lifted her and it's pretty clean. One of the advantages of fresh water I guess. Another pleasant surprise - no Zebra mussels. Only thing really hanging in the water is the speed-over-water paddle wheel (other than the essentials).

In talking to the marina owner he stated his lift weights were +/- 500 lbs. Final tally was 41,600 lbs. Like Queen said - fat bottom girls....

For some reason Hatteras had the 1978 43 FB/DC listed at 39k for that year only. All other years listed at 34k. Why this is I haven't a clue.