Ok so the BOM got it wrong and the predicted 30-knot winds and 3 meter waves didn’t arrive.
So I finally got to do my water test and I must say I was very happy with the results.
First off I had an old 19p 3 blade prop on and found the thing didn’t have enough thrust to steer the boat properly at idle, Which is strange because the old motor had a 4 blade 17p so their must be a slight gear ratio change there.
With the 3 blade prop it still went well under high revs but it did want to rev higher than I liked, also hole shot was awesome, in fact too awesome LOL.
Piece of advice don’t try this without securing everything in the boat first LOL, I went from Idle to full throttle and everything that wasn’t tied or bolted down in the front of the boat ended up in the rear of the boat in a milli second LOL
Given that I headed back to the ramp and swapped the 19 p prop for a 21 p 3 blade prop and headed back out again.
This was heaps better, Hole shot as expected was down a little from before but still pretty good and WOT at around 4700 rpm doing 65kph 35 knots. This is a 10kph improvement from the old engine and I think there is still heaps of room for more improvement.
I’m Still running the standard Holden computer chip at this stage as it gives me a starting point to change things, but over all I think the standard tune is pretty good and fairly well suited to the boat.
Exhaust manifolds at full noise stayed nice and cold and basically everything did what it should be doing.
I think the prop may have a slight slippage in the bush as the motor seemed to intermitantly rev slightly higher for no reason and the prop nut was loose when I got back home.
I would also like to make the whole thing a bit quieter and will be putting some extra sound deadener foam in the engine bay, It is better than the old 470 motor for noise but again there is room for improvement.
Why do cars run pretty silent at 3000rpm and boats sound like a rocket ship LOL,
Here is a bit of video looking over the transom while under way Please excuse the shoddy camera work as it is hard to shoot video and drive a boat at the same time LOL, (Lucky there isn't a law against it yet)
Cheers Andy