Going back to the origin of this rather lengthy thread I had another visit to the boat doctor and more sea trails this afternoon and think the setup is now right. I already have 41.5 hours up withthe “old” setup (mark 2) and it was apparent, particularly with heavy load or unsettled sea conditions, I was still having trouble getting traction and did a big reef runin sloppy seas Sunday and did 257 k’s on 272 litres.
Today dropped the motor another 2 notches and sea trialled another prop. Ended with the sort ofnumbers I had been hoping for and with the RX 18. RX 16 was not enough prop and produced much worse numbers. Only worry is that the RX 18 is not getting theWOT revs but I virtually never travel anywhere near WOT and while I know not getting full revs means I may be loading the engine, the performance and numbers speak for themselves.
Nice easy plane at 3950rpm. 38 lph 45kph econ gauges bouncing between 1.1 and 1.2
Best numbers cruise speed
4250 rpm 41 lph 49kph econ on gauges 1.3
Accelerated well
4400 rpm 43 lph 51 kph econ 1.2
4600 rpm 47 lph 53kph econ 1.1
4800 rpm 54 lph 56kph econ 1.0
5000 rpm 62 lph 64 kph econ 1.0
5200 rpm 67 lph 66kph econ 1.0
WOT only gets to 5350 92 lph 72 kph econ .8
These are the RX 18 numbers. RX 16, while getting to 5850rpm WOT was very inferior across the rev band and achieved 69 kph WOT.
I'm now done "trialling" and will take what I have got. My original Yammy set up was burning 370 litres to do my 'Sunday Run". This was back to 272 litres used last Sunday in hard running conditions. Based on todays numbers, also in fairly sloppy conditions, I will get this down to about 220 litres. As to oil burn I have used 17 litres for 41.5 hours, most of which has been running hours, only about 8 trolling and most of these hours have been running at around 4800 rpm. Until today this was the best return at 1/1 litres to kilometers in heavy sea and with full load due to a lot of slippage in the lower rev bands.
This thread may carry on for a bit now about the Minn Kota Ulterra but as far as my project to upgrade my reef boat from a 250 4 stroke Yammy to a 300 Gen 2 Etec it is now done. As at today, on my average reef trip I will run faster and save in the order of $210 in fuel per trip, offset by $60 in oil. $150 better off for around 50/70 days a year and no need to get the motor serviced, virtually every month with the hours I do. A lot of local commercial operators are watching over my shoulder who are all running big, and often multi, Yammy rigs. I think Etec are about to take the Whitsundays by storm. Nobody in business can afford to ignore the numbers when they are running outboards for 1500/2000 hours a year. If you took my numbers, times 2 big yammy's it would be, potentially, in the order of $168,000 a year in fuel saving. (2 motors. 30 LPH/engine, $1.40/l, 2000 hrs/annum), offset by $60,000 in oil but without even going to service costs.
Great project. Thanks for the amazing interest and input and maybe see you on the water one day.
kc
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