Bringing her home

[Sprig1]

Hi Doug and Tom no I never got Vic's sound blanket. I try to talk to Vic every month or so. He's doing well. Doug it sounds like we have the same props. I run the same speeds and rpms as you also the decibels. I thought I did a good job sound proofing but I guess I failed. I think the bigger prop would help so less rpms hopefully less noise. I don't know much about props. But being over propped a little is ok I guess. We don't run these boats hard it's more of a leisurely crawl and as you say they aren't going any faster with more rpms or horsepower. I have a another prop halfway between the one I am using now and Tom's. I just have to figure out if it fits.
The people putting Beta engines in should know how much horse power it takes for hull speed. I don't know how to figure that. Does anyone have a power curve chart for a 4d61? I am getting above my pay grade here. It would be nice to know if we are over reviving or motors for the speed. I probably explained it wrong in trying to get my idea across.
They are just noisy motors! The rate I'm going I'll be deaf soon and it want matter.

[DCatSea]

Onto props: There is once again a really good thread on A25/A27 called "Requesting opinions on 4-blade v 3-blade props for 27FC"
(Search 'propellers' in the thread). Beta Don's note of Sat Oct 10, 2015 10:43 pm is very useful and informative.

[motthediesel]

That's a good link -- thanks Doug!

I guess my first impressions were right, my 19x12 is a huge wheel on one of these boats.

The study of propellers is an interesting one because it still is as much art as science. I remember reading years ago in Skene's "Elements of Yacht Design" that during WW2 they had to make huge changes to PT boat props when they sent them to the Aleutians, just because of the water temperature -- crazy! Do you have Dave Gerr's "Propeller Handbook"? That's a real good read on the subject too.

Looking forward to Summer 2020 when I can do some more complete testing of our setup. Us owners of Peugeot-powered A-27's should pool our data. Maybe we can reach a consensus on the thorny old "best prop" debate --- or not

Tom

[motthediesel]

Does anyone have a power curve chart for a 4d61? I am getting above my pay grade here. It would be nice to know if we are over reviving or motors for the speed. I probably explained it wrong in trying to get my idea across.
.

Chris,

If you have access to the "Documents" section here, go there, look in the "Power" section, then "Lehman". There is a PDF of the original engine owners manual there, and it has a power curves graph for the 4D61 on page 11. Max torque, minimum BSFC both around 2300 rpm.

I received an original copy of that in my "Ships Documents" binder that came with the boat, but I know not everyone is so lucky after 35 years. If you don't have access, PM me and I'll scan the page for you.

Tom