Speed question

Timmah · #1 24-05-2009, 10:17 PM

Hi guys,

I have a question in regards to how fast my motor should be taking me. I'm not really wanting to go to much faster but I want to get good fuel economy and the likes and if something isn't right I would like to fix it. I have a 4m stessl with a 3 cylinder 2stroke Yamaha motor, decking, 100 litre livewell. When I have a second person on board I can only get about 20knots roughly out of it on a really flat day. Is this about right?

Cheers
Tim

StuKlose · #2 24-05-2009, 10:42 PM

Tim
The figures you have quoted would roughly be equivalent to a 30hp motor. What size motor are you running?

Timmah · #3 24-05-2009, 11:33 PM

Oh yeah it's a 30hp. That would help if I told ya

Cheers
Tim

Richo · #4 25-05-2009, 01:33 AM

You may be able to squeeze another couple of knots out of it...... my 40hp version of your donk is on my 4.2m Explorer and I can get about 28knots with 100L livewell full and 2 blokes in it. Can only get about 27knots when on my own, the extra weight seems to give me a smoother ride, thats the bugger with no trim.

cheers

Mandurah Marine · #5 25-05-2009, 01:36 AM

What sort of drop in speed with what sort of weight change. Do you know if outboard height is correct and what rpm you are achieving at WOT (wide open throttle)?
Ideally you should test WOT with fair average load (persons, fuel, livewell, gear, esky etc), then prop to suit whilst ensuring engine height is correct. Your 3cyl 30 should carry load variation quite well because of it's cubic capacity, but only if it is propped correctly. WOT should be as close to max recommended rpm as possible for the motor. Propping correctly is too often overlooked but put simply if overpropped it can be like driving a car at 40kmh in fifth gear and under propped like 40kmh in first. Not good for your engine or your fuel economy or performance

Lone Ranger · #6 25-05-2009, 08:41 AM

If I recall with 2 people on board, a few rods and x 2 tackle bags on a 3.95 fully decked dinghy, empty 116 litre livewell with MK, x 2 batteries on board on a 30hp, with anchor, small fire extinguisher and spare 5 litre of fuel .... I could go max at 23knots. I tested that when I was new to boating but could probably do more than that.

HTHs.

breambasher · #7 25-05-2009, 09:18 AM

I own a stessl edgetracker 3.85 with full floors, small 60-70 L livewell, two batteries, 25 litre of fuel, 2 blokes and a few rods each plus lure bags etc and the mercury 25hp with solas prop gets me a tad under 23 knots on a good day. so I considered that reasonable enough.

Tanc · #8 25-05-2009, 10:04 AM

Sorry bud, I'll try to loose some weight