You really do meet the nicest people on Ribnet
However, I have never met GordyP, but thanks to him I have been able to check out a 19" Apollo, and he has saved me from making an expensive mistake. Thanks very much for the loan of your prop Gordy, you are a gentleman
The numbers first. The nearest diameter for a 19" Apollo is 14 and an eighth (358.8mm), whereas the 21" already mentioned in post 18 is 14 and three quarters (374.7mm).
With the 19" Apollo fitted the maximum two way runs were 40.8 knots @ 5500 rpm and 44.8 knots @ 5600 rpm in the other direction.
So whilst gaining 2-300 revs, I have lost 3 to 4 knots at the top end, and to be honest the boat did not feel as responsive, in particular acceleration seemed down.
At this stage I have to admit that I was struggling with the concept of an engine that I was being told should rev to 5650 – 5850 in order to be most efficient and get maximum speed. By bolting a larger pitch (and incidentally larger diameter!) propeller and seeing lower revs I was getting better performance.......
I was starting to think that my engine had a torque peak a lot lower in the rev range than the maximum power peak. It seemed to me to be the only possible explanation. A conversation with the local etec dealer confirmed what I had been thinking. He stated that the mapping of the 2.6L 200 is different to both the 150 and the 175 etecs, and that there was no point in getting 5600 or 5800 rpm as I would see no benefit; and he went as far as to say that 5300 rpm for my engine was OK! It has been mapped to give a much lower torque peak.
What about the lugging that has been mentioned on the etec owners forum? Well, I have some little experience of two stroke engines, and mine did not feel like it was ‘lugging’ with the bigger pitch prop, it felt responsive. My understanding of “lugging” is that the engine is not running efficiently and infact opening the taps to accelerate produces little or no increase in speed. In addition the fuel and oil consumption will suffer. So the feeling of lugging is not quantitatively testable. What is testable is fuel consumption.
So, the other day I set out with the 19” Apollo fitted and did some runs to get the fuel consumption at 20, 30 and 40 knots. Unfortunately due to the lively conditions I could not get figures for two way runs, also I have no idea of the accuracy or otherwise of my fuel transducer. These factors do not matter, providing transducer error and sea state is consistent, as all I was interested in was the relative fuel consumption using the 19” and the 21” Apollo props. I guessed the worst case reading error to be +/- 10%.
Having completed the runs with the 19” prop, I went back to the slip and changed props to do some further runs with the 21” Apollo. The results are below. I tried my best to be accurate in my readings and to NOT bias the results either way; I purposely hid the results for the 19” prop when doing the runs with the 21” prop. I was being bounced around quite a bit, so trying to maintain a constant speed and get good readings was not easy!!
Speed (knots).......19" Prop Fuel Consumption (ltrs/hr).......21" Prop Fuel Consumption (ltrs/hr)
Whilst I consistently recorded lower fuel consumption with the 21” prop the results are close in my view, and within the +/-10% (just) that I had estimated. What is proven is that the fuel consumption is not higher with the larger pitch prop. In my view the engine is NOT lugging!
So, what about going further and trying a 23” Apollo. Sorry, I have spent enough, and I am happy with the performance of the 21” Apollo.
I am not saying that the Apollo props are the best there is for my engine, or etecs in general. What they are are a reasonably performing prop at a reasonable price. If however you buy one you most likely will not pay the advertised price, as the lovely people from HMRC like to take their cut
I am also not saying that all etecs perform in the same manner, this lower torque characteristic for the V6 etecs is peculiar to the 2.6 litre 200’s.
Yes, this goes against the conventional wisdom, as quoted by many on the internet. Nevertheless, the figures speak for themselves. I am happy, my boat feels more ‘alive’, and just all round better performing. Can’t help wondering how it would feel with the right 4 blader though.