JP3 serial number ID help

[SnippetySnip]

Hi Everyone,

 

 I’m new to posting on the forum, but have read lots of useful threads on here, thank you!

 

I have recently acquired a boat with a lovely JP3 fitted, and was hoping to find out a bit more about the engine. How old is it? What subtype is it? 
 

I attach a photo of the serial number plate. It’s not a very legible image, so my translation is: No. 125273R4 HP 27 RPM 1100

 

It doesn’t seem to fit the format of the Lister serial number sources I could find on the internet! I’m hoping that you experts here will be able to offer some ideas. 
 

Thanks all!

 

Guy

[David Mack]

Yes. That's an odd one. But not the first I've seen on a Lister. 

Odd too that it's rated at 1100 rpm. The early 9/1 engines were rated at 1000 rpm but the later 18/2, 27/3, JP and JPM engines were rated at 1200rpm.

The serial number on a JP is always a bit of a gamble, as being mounted on the engine side cover it is all too easy for the side cover to have been swapped for one from another engine.

What type of JP3 is it? An original marine unit with Blackstone box and cylindrical water-jacketed silencer? An industrial engine with the flywheel on the 'wrong' end and a marine gearbox grafted on? Or an industrial which has been professionally converted to near original marine type?

Edited August 28, 2023 by David Mack

[SnippetySnip]

I was hoping the serial number might hold some clues, but to answer as best I can:

 

I'm not sure about which JP3 type it is, an engineer (during survey) commented that it might be an original Marine type, but I'm not sure on what basis he said that. What are the key features that I should look for?

 

The gearbox is a PRM 160D2 possibly not a lot older than the boat (1995) serial 0508151F00450.

 

The flywheel is at the stern end, so "on the right hand end" if you are looking at the side with the three crankcase covers.

 

If it is a conversion, it would have been done professionally when the boat was built in '95.

 

Thanks again!

[David Mack]

Sounds like a converted industrial - probably ex WW2 searchlight generator engine*. Is this by chance a Steve Hudson boat? He fitted quite a lot of JP3s like this.

Does it have the water pump fitted to the cylinder head nearest the flywheel and belt driven from the crankshaft, or a blanking plate where this would originally have been?

Are the decompressors on the cylinder heads or down on the large side cover on the side of the engine?

 

* Another thought. Does the non standard serial number and running speed mean thus engine was supplied directly to an equipment manufacturer for use in something unusual?

[SnippetySnip]

This is all very interesting! You're dead right, it is a Hudson boat, so I won't be able to ask him about it! I have an old survey from 1999 which describes the engine installation pretty much to a tee as it is today. So, I'm guessing the refurb don't at the time of installation has stood up quite well to the test of time, nearly 30 years.

 

The water pump is a separate Jabsco pump fitted to a bracket in the engine sump. Coolant circulates round a calorifier and port-side skin tank. I will have a look for a blanking plate when I'm next onboard.

 

Decompressors, we have levers on the tops of the rocker covers, and high/low compression valves on the side of the cylinder heads.

[Steve56]

This range of engines was built between 1931 and 1952. If it is fitted with the correct number plate that would make your engine1942.