|I have finally finished all the work on INMA and have completed trials to make sure any changes worked. |
Perhaps the most controversial change I made was to shift the outboard off the bracket on the stern and put it back in the well per Rob Legg's original design.
I have said enough about why I did this, this post is simply a report on the boats performance with the 5 hp short shaft Mariner in the RL24 Mk 4. We tested it thouroughly earlier this week and I am now confident that the yacht's performance under engine is about as good as I can get. We tested in full cruising trim, Keel and rudder down so that performance is typical of future capability (no dreaming)
In calm water at full throttle, the yacht holds 5.5 knots which is hull speed. Reduced throttle reduces speed with a comfortable noise/throttle allowing a 4.5 knot speed.
Directly into a 15 knot wind with Port Phillip Bays short sloppy chop, the hull held 4.5 knots at full throttle (up and down the waves). There was no cavitation or any indication of handling problems etc.
Directly downwind in a 15 knot wind, with Port Phillip Bays sloppy chop, the hull comfortably held 5.5 - 6 knots. With a bit of shifting people forward and leveling the trim, the hull comfortably planed between 5.5 - 8 knots.
In the St Kilda marina, the yacht handles properly with excellent manouverability. The lack of reverse thrust (and cavitation in reverse) is noticable when idiots cut across the bow but otherwise we cope.
We can't waterski but the high thrust prop makes every horsepower work.
I had a long shaft Honda on the stern and was impressed with its reliability and performance, the Honda or for that matter other new outboards would not fit in the well, hence the Mariner 5.
As part of putting the outboard in the well, we have been able to add a BBQ over the stern, add a tiller pilot on the starboard side, a solar panel on the port stern and put a bimini behind the boom. All of these luxuries were difficult or impossible to have with the stern mounted outboard, where as now they all work without clashing with a very practical layout. Weight and the distribution of weight is improved because the weight of the new equipment is less than the weight of the bracket and old outboard.
Would I do it again, without hesitation. The 5 hp is enough for me, I would prefer an 8 hp but they do not fit and I would prefer a 5hp in the well anyday to a 8-15hp on a bracket on the stern. I just love docking between the powerboats and backing into my spot without the circus act of shifting gears and backing into the jetty.