Diesel fuel economy calc, algae killer additive

[Man-O-War]

How can I calculate diesel fuel economy (approx)?

130hp Volvo Penta turbo diesel, on a 23ft RIB (see pic). At cruising 3200rpm it goes 18knots

Also, what is the good algae killer additive for diesel tanks?

tnx

[Uno Breath]

Ribs get such great fuel economy who cares? Now my boat only getting 1 gallon per mile. Thats when it starts to matter.

Edit- Kick a$$ RIB, i'm jealous.

[bug_power]

man where did you get that boat, and how much did it cost? I'm a school teacher with caviar Dreams!

[KEYSKILLER]

you could get a fuel flow meter, find that sweet spot in all conditions.

[dagodiver]

you could get a fuel flow meter, find that sweet spot in all conditions.

Best for sure.!




Numbers are as follows;

1 gallon of diesel will make 18hp for 1 hour
1 gallon of gasoline will make 12hp for 1 hour

Remember when prop sizing a boat if gas you prop to RPM's if diesel you prop to manufacturers fuel burn at WOT.


Sooooo if you are using 70% of your HP to cruise out of 130 than;
130X.7=91 and 91/18=5.05 gph

This of course could be way off depending on the shape of your engine.
If all is well and the 70% is the magic number than you should be close.


Dago.

[Man-O-War]

I am using gasoline props (got them for $75) but they put me at same RPM at WOT as Volvo recommends. I am probably using 80-85% to cruise, so 6+gph sounds like a safe assumption. Good thing is I can cover 22 miles in an hour :) .....for $16 in fuel

I paid $5750 for the boat and trailer. Came with radar and extra (over)props and stuff.

[Uno Breath]

I am using gasoline props (got them for $75) but they put me at same RPM at WOT as Volvo recommends. I am probably using 80-85% to cruise, so 6+gph sounds like a safe assumption. Good thing is I can cover 22 miles in an hour :) .....for $16 in fuel

I paid $5750 for the boat and trailer. Came with radar and extra (over)props and stuff.

I can cover 22 miles in just over an hour but its going to cost me about 90 bucks. You got a killer deal on a great boat.

[OceanEd]

There are several good diesel additives out there. You can buy 2 or 3 different types at West Marine. Biobor is one type.

[JLittle44]

Good thing is I can cover 22 miles in an hour :) .....for $16 in fuel

I paid $5750 for the boat and trailer. Came with radar and extra (over)props and stuff.

That is one hell of a deal. I am crying.

[WonderBoy]

I use Bio-Guard. Recommended by all the sportfish guys we spoke to in Stuart, Ft. Lauderdale and Bahamas.
As for your economy, you suck! :)

[Man-O-War]

Thanks for the additive info.

Don't be hatin' on the boat, I got it the day AFTER I decided NOT to get a boat :eek: just could not pass up a deal like that.

Two reasons for the price: idle was 625rpm and engine was shaking at idle (tightened the screw and made it 750rpm, smooth), and it could not get up on a plane (over-propped, got pair of used props for $75 and fixed that).

;)

Deals are out there

[dagodiver]

Tell me it was the Govener buffer adjustment and that the engine was "hunting".? That one gets alot of people.


Dago.

[kaborkian]

Man..what a deal.

If you're new to diesels, pay for a year of boatdiesel.com and read a lot. Good information to be had.

Generally speaking, you should prop your engine so it can achieve slightly higher than maximum rated RPM at WOT, then run at 70% of full power (not 70% RPM...). That will get you close to the best fuel economy and longest life out of the engine.

Based on my engines, burning ~12 gph at 245 horsepower, you should be around 4.5gph at 91 horsepower. That's 4 n-mpg...impressive to say the least.

[Man-O-War]

It was the idle screw...the stop screw that throttle return spring bounces against. It literally took me 1 minute to diagnose and fix.

How do you figure out 70% of power? Using the throttle lever? I always go by RPM....cruise 3200rpm (18kts), full tilt 3800rpm (24kts)

[bug_power]

you let me know if you see a deal like that again! I'd hate to have to leave the teaching profession so I can buy me a RIB :)
Our childrens futures are at stake!

[islandpressure]

Stringer Bell look at a product called startron,I use it and its the best!!!!!!!!!!

[kaborkian]

From a power calculator at boatdiesel.com, 23' boat at 5000 lbs:


SAE HP Max Kts*
131 24.3
115 22.7
102 21.4
93.6 20.5


So, your 18 knots is conservative, and could be increased a bit I think. You really need to research your specific engine to see what cruising speed (rpm) you should use, but it sounds to me like you can step it up a couple of knots.

[Man-O-War]

Thanks kaborkian. My 18kts is cruising speed (not max speed). Max speed is 24kts, but I almost never take it up to 3800rpm full tilt

[kaborkian]

Thanks kaborkian. My 18kts is cruising speed (not max speed). Max speed is 24kts, but I almost never take it up to 3800rpm full tilt

Yea, I got that part. What I was trying to show is that 70% power is actually around 20 knots though...

[Steve-o]

Hey buddy,

You can run that engine all day up to 3600 rpm according to some of the VP gurus on boatdiesel (assuming you really can reach 3800+ WOT.....not going by the non-trusty volvo tach). Glad you got it sorted out, nice ride and killer deal!

[Man-O-War]

Oh, got it Kabo.

Santiago, thanks for all the advice when I was sorting it out! Runs like a dream now. I had a laser RPM meter, but gave it away to my dad thinking that I won't be needing it now that stock tach is hooked up correctly. Guess I should've kept it to measure exact RPM

[gogators27]

Stringer, since you decided not to buy a boat (and that was the right decision), let me help you out by taking the boat off your hands and putting a couple thousand in your pocket for you troubles!! I like that boat!

[Man-O-War]

:)

Gator, there are deals on nice RIBs all the time...I was gonna get another one, but it was all the way out in SoCal....pretty good deal as well:

http://cgi.ebay.com/ebaymotors/Inflatable-RIB-24ft_W0QQitemZ220102084712QQihZ012QQcategoryZ31271 QQssPageNameZWDVWQQrdZ1QQcmdZViewItem