Originally Posted by Jono
Thank you for your input, that is an interesting observation, John. Are you, if I read you correctly, inferring that most people donít bother to set up a boat as well as you do? Itís just that Andy and Frank put an awful lot of sea time and effort into setting up my boat and Iíd be very disappointed if I thought they werenít experienced enough to get it right. Should I be going back to them and saying that my boat should be more economical to run? Bearing in mind we set the boat and prop for the conditions that my boat has run at most of the time.
Also Iím intrigued by your question of the choice of two strokes for commercial use and the inference that it because of better fuel consumption figures. I understand that people who need to do maintenance ďin the fieldĒ would choose two strokes and that people who expect their engines to be abused and need overhauling would choose two strokes, or that people who need to go as fast as light as possible would choose two strokes.
Where do you get the figure of 90% from? I appreciate you have vastly more experience than most of us in the commercial field, but I have been wracking my brains to think of all the commercial RIBs that I can and can only think of ones with four strokes or diesels. Is the two-stroke ďmarketĒ a particular sector of the commercial boat world? Off shore/Rig work?
Thanks for your points.
With regards to setting up then my coments certainly do not include Andy or Frank or infact other manufacturers. Invariably it is the consumer or end user that can cause issues by dictating a certain engine or layout. Whilst the builder will have the expertise the client will often push in a certain direction for an engine on the basis of perceived fuel figures. Most customers also push for max speed and this can be costly in terms of fuel.
In fairness it is much easier to balance a 10m or larger than say a 5m for obvious reasons. What you can try is using your variable masses (people/equipmment) around and seeing if there is a change in speed and consumption.
Hulls must be kept clean. A moored vessel with a thin veneer of slime will add at least 15% to fuel. Plugs also. Change them before they break down and on a new set you can see up to 10% fuel saving. Top this off with a regular dolup of decarb/engine tunner.
Even steering will add to the equation. A poorly fitted cable steering will require a lot of course corrections as a result of oversteer. A well fitted hydraulic stystem will require less and thus fuel agin.
All in all the are a multitude of reasons that will affect fuel rates and what I am suggesting is that there is no genuine level playing field for test data. Indeed much testing is on US bass boats where there is little comparison to our uses. Thus when chosing an engine pay more attention to things like power to weigth ratios/a sensible max speed/layout of the vessel etc etc and a little less to manufacturers figures.
My quote of 90% use 2 strokes is in the larger pax RIBS. We have purchsed over 40 200-250hp engines this winter with only one pair being 4 stroke. We are about to evaluate a pair of YAM250 four strokes and a pair of Suzi 250 four strokes but for acceleration we prefer the 2 strokes and find that with the likes of ETEC there is no fuel diff. The Suzi 250 looks like it may be a contender.
On the ETECS we have fitted a number of 200 and 225s, all in pairs. We also use these in our own pax ops. A few hundred hours have been clocked and they would seem to be the dogs danglies. Give it another 1000 hours and we will know for sure.