how many LPH should I be getting roughly please?

ollyit · 08 July 2008, 08:05

Going to get the 5.4 wet quickly tonight for the first time - the boat has no A frame and just 2 people onboard, stand 3 man console, + 22 litre tank at the moment, its a yamaha 60 2 stroke (about 105ish kgs) - what should I get just pottering around at 20-25knots please?

thanks guys

Nos4r2 · 08 July 2008, 08:45

Same as you would on the sr4 at that throttle opening (not speed

)

Out of interest what prop is on there?

ollyit · 08 July 2008, 08:49

15" - smaller one, I'm probably guna bung on the standard yam alloy 17" pitch one - your thoughts?

Nos4r2 · 08 July 2008, 08:54

Quote:

Originally Posted by ollyit

15" - smaller one, I'm probably guna bung on the standard yam alloy 17" pitch one - your thoughts?

Start with the 15" and take the 17" with you to swap over if it revs too high. I think 17" might be a bit much.

Searider · 08 July 2008, 09:42

I seem to remember getting about 1.25 miles per litre at 25knots in my 5.4. Approximately.

ollyit · 08 July 2008, 10:19

thanks mate, what engine did you have? a 60hp also?

Pete7 · 08 July 2008, 10:42

Quote:

Originally Posted by ollyit

Going to get the 5.4 wet quickly tonight for the first time - the boat has no A frame and just 2 people onboard, stand 3 man console, + 22 litre tank at the moment, its a yamaha 60 2 stroke (about 105ish kgs) - what should I get just pottering around at 20-25knots please?

thanks guys

Olly, I think Duncan had a Mariner 75 on his. Nearest I can come up with was my Osprey Sparrowhawk and a 3 cly 60hp Merc (designed by Yamaha). Probably similar overall weight (hull lighter, but had A frame + big built in tank) and used 5 gallons per hour with a top speed of 26 knots (30 mph) lightly loaded). 20 - 24 knots with 4 divers and kit used about the same fuel.

From memory you have a bigger slower turning prop compared to the Merc 60 which is good news as it won't ventilate as badly when bouncing through the waves. As Nos suggests start with the 15" prop but you must have a rev counter to confirm the WOT or risk overloading the engine with the 17". Strangely I have a suitable rev counter in the garage if you don't have one

Pete

Doug Stormforce · 08 July 2008, 11:32

Quote:

Originally Posted by ollyit

the boat has no A frame and just 2 people onboard, stand 3 man console, + 22 litre tank at the moment, its a yamaha 60 2 stroke (about 105ish kgs) - what should I get just pottering around at 20-25knots please?

I would have thought about 20lph at full throttle

Searider · 08 July 2008, 13:12

Quote:

Originally Posted by ollyit

thanks mate, what engine did you have? a 60hp also?

I had a 90hp mariner 2 stroke. So, I guess it was fiarly unstressed at 25 knots.

With your 60hp being lighter you might do better than I did?

For a given speed you will be using the same HP irrespective of the max power of the engine. Fuel consumption should be comparable unless you are having to thrash your engine flat out to make the speed you want.

Hightower · 08 July 2008, 18:12

My 80 yam manual stated that it used 35 LPH at WOT. I guess 30 wouldn't be far off and would give you a safety marging too.

ollyit · 09 July 2008, 08:31

Quote:

Originally Posted by Pete7

Olly, I think Duncan had a Mariner 75 on his. Nearest I can come up with was my Osprey Sparrowhawk and a 3 cly 60hp Merc (designed by Yamaha). Probably similar overall weight (hull lighter, but had A frame + big built in tank) and used 5 gallons per hour with a top speed of 26 knots (30 mph) lightly loaded). 20 - 24 knots with 4 divers and kit used about the same fuel.

From memory you have a bigger slower turning prop compared to the Merc 60 which is good news as it won't ventilate as badly when bouncing through the waves. As Nos suggests start with the 15" prop but you must have a rev counter to confirm the WOT or risk overloading the engine with the 17". Strangely I have a suitable rev counter in the garage if you don't have one

Pete

Thanks pete, I'll let you know the score