Urajio

Hello! This is almost a detective story, since I'm trying to find info that is more than 30 years old.
There is an old patrol boat made in Japan in 1990. It took a while to research its specs (and decode old worn Japanese marks), but eventually I did it.

So its specs are:
Boat Length (13.4M)
Boat Beam (3.45M)
Boat Displacement (8.9 MT)
Application (Patrol ship)
Max Deadweight (2.2 MT)
Max Draught (0.55 M)
Light Craft Mass (5400 KG)
Min Freeboard (0.9M)
2 Engines (Detroit Diesel GM6V-92TA-Hi)
Engine HP (550 HP @ 2300 rpm)
Propulsion System (ASD12 Arneson Drive)
Marine Gear (MGN133-2R)
Reduction Ratio in the marine gear (1.50)
Cont. Rating in the marine gear (445 HP / 2170 rpm)

The current props are two 3 blade old design Rolla props, upon which is stamped Rolla Bil. Dinamico LH 01-91, Rolla Bil. Dinamico RH 01-91. I don't know what numbers 01-91 mean, maybe model number or production date.
Their diameter is 30" and I don't know the pitch yet. I wrote to Rolla, and I hope they will help to determine the props model, but there was no answer from them yet.

So my most important task is to determine whether these props were the original boat's props or not.
Since the boat has ASD12 drive, it means it used surface-piercing props.
I wonder if the current props are surface-piercing and compatible. Maybe somebody could identify them?

I contacted the ship's manufacturer in Japan and they have sent me the registration document on that boat, but unfortunately props model is not mentioned in it.

All photos and registration document are here jjjdrive.google.com/drive/folders/1WbwtgtEUjhgb0N7-RR0k8oQP7C5bqa-6?usp=sharing
Please remove jjj in the beginning (I cannot normally post links here yet)

I really hope someone would be able to help me crack this case!

resurrected

Welcome to OSO. That sounds like a very interesting project you have found. I don't think finding the "original" propellers is really that important. Propeller technology has come a long way since then, test what you have and go from there. What are you doing with the boat? Converting it to pleasure or building a museum piece, or something in between?

Urajio

Thank you for your reply! This is not my boat, I was just asked to help find the answer to that question because I know Japanese So I don't know the details, but the owner really needs to find info about the original props, not the props themselves (they need this info to resolve some sort of conflict). I guess they will eventually order modern design props and use the boat for some more time (well, on photos it seems to be still in a fairly good shape). But turning it into museum is an interesting idea - while investigating, I also found a Japanese article on patrol boats' history, and this boat was mentioned there! Without props' specs unfortunately.

So, I'll try to call Rolla tomorrow I guess. Really hope they could find that info.

Griff

Highly unlikely that Rolla will be able to tell you if they are original to the boat.
Most likely, only the boat manufacturer will know exactly what props were OEM on it.

rak rua

Here’s your link to a bunch of photos. Interesting old boat, Detroits and Arnesons were probably an expensive combo at the time.

drive.google.com/drive/folders/1WbwtgtEUjhgb0N7-RR0k8oQP7C5bqa-6?usp=sharing

RR

Edit…. Doesn’t show as a link, gotta cut and paste it……sorry….