1986 Perkins 4-236 Fuel Consumption

[Kenatsea]

Ok, for me it's a lazy afternoon and I'm thinking about my new to me boat and dreaming of all of the anchorages I'll go to. And I was wondering about fuel, specifically consumption and range.

Now I know I can/could take it out and figure it out on by own but, I probably will not be able to do that for several months into the future as she is far away right now and on top of that I still have a few thing to repair/replace before we take the 2nd. maiden voyage. First was sea trial, now she's down for the upgrades.

So she has the Perkins 4.236 I was told it is 85 HP but I've seen on here and google, anywhere from 67 - 85 hp. depending on a few things. My boat has a 43' waterline and displaces ~40'000 lbs. hull speed of 8.3 kn. and I imagine economical cruise speed of around 7 kn.

Can anyone give me a best guess of what my fuel consumption might average?

Thanks,

[jak3b]

Originally Posted by Kenatsea

Ok, for me it's a lazy afternoon and I'm thinking about my new to me boat and dreaming of all of the anchorages I'll go to. And I was wondering about fuel, specifically consumption and range.

Now I know I can/could take it out and figure it out on by own but, I probably will not be able to do that for several months into the future as she is far away right now and on top of that I still have a few thing to repair/replace before we take the 2nd. maiden voyage. First was sea trial, now she's down for the upgrades.

So she has the Perkins 4.236 I was told it is 85 HP but I've seen on here and google, anywhere from 67 - 85 hp. depending on a few things. My boat has a 43' waterline and displaces ~40'000 lbs. hull speed of 8.3 kn. and I imagine economical cruise speed of around 7 kn.

Can anyone give me a best guess of what my fuel consumption might average?

Thanks,

Mine, a 1968 4-236, at 1800 burns around a gallon an hour.

[Kenatsea]

Thanks for your info. Can you tell me your speed at 1800 rpm?

[Lepke]

From Perkins data sheet:

[HankOnthewater]

I have the same engine, 85 HP when new, and now with nearly 10,000 hrs, maybe 75-80 horses left.
My boat is similar to yours, a little bigger, and I have a max prop (to be replaced next few weeks).
I use approx 4.5 lt per hour running at 1500 RPM. I do then 6 to 6.5 knots, in fairly flat seas, 5 to 5.5 knots in a chop. And if you want the real calculation is 4.34 lt per hour. When running at 1800 RPM I use around 5.5 to 6.0 lt per hour, doing 6.5 to 7 knots in flat seas
But..... speed depends a lot on sea state and the prop used!!

on edit: just see the graph above, hmm my use is a lot lower than that.

[StuM]

Originally Posted by HankOnthewater

I use approx 4.5 lt per hour running at 1500 RPM. I do then 6 to 6.5 knots, in fairly flat seas, 5 to 5.5 knots in a chop. And if you want the real calculation is 4.34 lt per hour. When running at 1800 RPM I use around 5.5 to 6.0 lt per hour, doing 6.5 to 7 knots in flat seas
...
on edit: just see the graph above, hmm my use is a lot lower than that.

Very similar at 1500RPM - 1.1 to 1.2 USG per hour = 4.2 - 4.5 lph (exactly your figure)


At 1800 RPM the published figure is around 1.8 to 2 USG per hour = 6.8 - 7.6 lph. I'd guess your variable pitch Max-prop imay be what is giving you better efficiency at the higher RPM.

[HankOnthewater]

Regarding above post by StuM
Yes, maybe the Max feathering prop helps, and also I believe I am over propped slightly. The plan was to reduce the pitch (in degrees) by two. realising that fuel consumption will go up. I took boat out of the water, and just now discovered a crack in the prop housing. The prop is 26 years old, and thinking of replacing that now with same, autostream or autoprop.

I should have added in my first post on this thread that fuel consumption is also dependant how clean the bottom is. My figures are are with a clean bottom. With some slime, light algae, the fuel consumption figure will increase easily (my estimation) by 10-20%, and a real dirty bottom maybe as high as an extra 40-60%, again an estimation.

[Kenatsea]

Thanks guys.

I also have the Max Feathering Prop installed, am told it's only a few years old. So for me conservatively this will work out to about ~800 NM range and to be honest a little more than I had expected, so I'm pleased with this.

Really appreciate the feedback!
-Ken

[Kenatsea]

Hank,

Would you mind sharing how you feel about the engine? To hear that you have 10,000 hours is great. Mine is sitting at 4,370 with a recent injector service and head work. Any recommendations for someone new to this engine to ensure additional years of service?

-Ken

[tarian]

Change oil regularly filters, and good fuel , your perkins is just breaking in 5600 hours on mine, 4236 is a legend in the engine market, look after it it will see you good

[Kenatsea]

Originally Posted by tarian

Change oil regularly filters, and good fuel , your perkins is just breaking in 5600 hours on mine, 4236 is a legend in the engine market, look after it it will see you good

Thank you Tarian!

[Lancerbye]

I have twin 4.236 Perkins on a 20 ton motorsailer. I usually cruise at 1400 to 1500 doing 6.5 knots on one engine. At that speed my fuel consumption is 4 to 5 litres an hour. I have Campbell Sailer props.

[Kenatsea]

Thanks for your data and input Lancerbye.

[SeeMonstrEd]

I have a 1996 Perkins M-90 (4.236) 85HP. My boat is very similar to yours 41,000 lbs. 45 ish waterline.
I have measured just over a gallon (1.1) per hour at 7kts.
As said before these engines are legendary workhorses. Mine has 8000+ hours and runs like a top. change the oil and filter every 100 hours or every 6 months whichever comes first. Replace the raw water impeller once a year. Keep the fluids topped off and she will last longer than you do.
I would rebuild this engine but never replace it.

BTW I have found the oil filter for this engine at grocery stores in small towns in the US.

[Kenatsea]

Originally Posted by SeeMonstrEd

I have a 1996 Perkins M-90 (4.236) 85HP. My boat is very similar to yours 41,000 lbs. 45 ish waterline.
I have measured just over a gallon (1.1) per hour at 7kts.
As said before these engines are legendary workhorses. Mine has 8000+ hours and runs like a top. change the oil and filter every 100 hours or every 6 months whichever comes first. Replace the raw water impeller once a year. Keep the fluids topped off and she will last longer than you do.
I would rebuild this engine but never replace it.

BTW I have found the oil filter for this engine at grocery stores in small towns in the US.

Great feedback, much appreciated.
-Ken