Perkins 4.236: 81 ,73, or 50 HP

[junkrigjohn]

I'm currently building a steel Bruce Roberts 39 and bought a second hand Perkins 4.236 which was advertised as 80HP.
When ordering the propeller I was surprised to find this engine is available in three options namely high speed pleasure 81 HP at 2800 rpm, general pleasure 73 HP at 2400 rpm , and heavy duty 50 HP at 1800 rpm.
The existing gearbox was found to be 3;1 , which would suggest the engine is possibly the heavy duty variant, whereas the 73HP option is what I require.
My question is, apart from the gearbox and throttle restriction is there any difference between the three engine options.

 

[gordmac]

Not sure but the different outputs are probably due to the different RPM, I think it has something to do with allowable time running at the different speeds from a durability point of view.

 

[Monique]

Not sure of the precise equivalent to the Volvo but to gain in power from 50HP to 80 HP requires the addition of a turbocharger.

Is your unit has a TC, then its unlikely to be 50 HP

GL

 

[TQA]

I have never seen a 4 236 with a turbo as OE.

A 4 236 will be a bit of overkill in a 39 ft boat. I had a steel 38 ft Tucker design with a 4 108 and that was fine. My current 44 ft has a 4 154 and i get 7 knts easily in moderate seas.

Still you have it and if it is in good nick it will do the job for years because it is not going to be stressed.

 

[Tranona]

The difference in output will be controlled by the governor - the higher the engine runs the greater the output. Perhaps a Perkins dealer will have details of how to tell which you have. The 3:1 box suggest it was fitted to a low speed heavy workboat as a 3:1 reduction will need a very lrge diameter prop - probably too big to fit your boat.

 

[essexboy]

Try Jason hatch at ludham Bridge Boatyard in Norfolk, served his time on Perkins, and a font of all things Perkins.

 

[Jim@sea]

I have never seen a 4 236 with a turbo as OE.

A 4 236 will be a bit of overkill in a 39 ft boat..

Nauticat 33's had a 73 hp Perkins 4.236 as standard equipment.

 

[bristoljim]

Nauticat 33's had a 73 hp Perkins 4.236 as standard equipment.

The pump fuel setting is unlikely to be different ,just the rating at different revs.If you use the 50hp @1800 this would need a 29" X 26" prop !!.If you keep the 50hp but at 2400 revs with a 2-1 gearbox this requires a prop of 20" X 13" .Much more important to change the gearbox ratio than worry about the rating - then fit a prop of about this size or slightly bigger depending if your priority is exploiting more engine power or having less drag.

regards Jim

 

[john_q]

A 4 236 will be a bit of overkill in a 39 ft boat. I had a steel 38 ft Tucker design with a 4 108 and that was fine.

Still you have it and if it is in good nick it will do the job for years because it is not going to be stressed.

I agree, I have a 40 foot Tucker steel boat with a 1984 4236M in it and rarely have to run it more than 1600 RPM, it uses 1 US gallon, 3.8 litres per hour at these revs

I think mine is rated at 72HP