Grady 330, f300 outboards best mount height and propeller type and size

[kirk a]

Watching this thread with keen interest, as a pair of 300's will be installed this winter on my 330.

 

[Sardinia306Bimini]

I wish I knew. Having them higher would help with clearing the tips of the gear cases when full of fuel and water.

It will probably not work on the 330 Express as it's a huge boat with a lot of forward weight, but worth a try.
You may have a big person walking to the bow while docked and watch if the added weight on the bow would clear the lower units a thad more out of the water without making her bow heavy at rest. Worst case could be that she start to bow steer and then it will become dangerous, but if not then it could lead to a more flat running with less trim tab what is usually more economic.
If you then you could move some weight forward or add some weight in the anchor locker to level her out when not moving.
As long it's only the tip of the lower unit I would not worry and just paint the submerged triangle with antifouling while it's more problematic if the water inlets remain submerged and stuff growing inside behind the screens. I had that on my Venture 34 and could only solve it with adding hydraulic jack plates, but that was a expensive and suboptimal decision and I would not repeat it again.

Chris

 

[Automated14]

I wish I knew. Having them higher would help with clearing the tips of the gear cases when full of fuel and water.
The Marlin didn’t gain any performance with engines higher but the boat didn’t feel as nice coming on plane as with the engines down.
Just my feedback anyway.

It goes against everything i've ever read on engine height. However, my antiventilation plates look to be perfect yet my boat is slower than others with same power. Not by a lot. losing 2-3mph. I may lower them down this winter. I can always put it back.

 

[Fido]

It goes against everything i've ever read on engine height. However, my antiventilation plates look to be perfect yet my boat is slower than others with same power. Not by a lot. losing 2-3mph. I may lower them down this winter. I can always put it back.

Exactly. It goes against what we all know and have probably learnt from other manufacturers. Our experience with the Marlin and now the 330 confirms that lower is best.

 

[Sardinia306Bimini]

Engine height depend on several factors and the "knowledge" that AV plate must be at transom edge level or a bit higher is universal knowledge and a good starting point on first installation of a certain outboard to a unknown hull. As i wrote before, to set the engine as highest up as possible is mainly a racing thing and can't be true for cruising boats like most of use have and use. On smaller boats >25 ft too low engine mounting can lead to proposing but porpoising is often/mostly a problem of wrong weight distribution making the given beat too bow light.

I installed a lot outboards, on my and on clients boats and mostly the rule AV Plate on transom edge or keel at single installations was right, but I had problems with Suzuki outboards on 3 of my own boats as on all 3 boats the same hole as the before repower installed Yamaha was leading to ventilation, either going over the hump and in tight turn. The only solution was to lower the outboard one hole more as the previous outboard was mounted and all was fine after that and I believe that the reason for that is in the bigger 16" diameter propeller the big Suzukis have and also that Suzukis like to run Suzuki propellers.
Trickiest was my Master Dive Rib where I bought it with twin Mercury on a bracket and repowered with single DF300 and it turned in a mess of trial and error with engine hight and different propeller till we set the engine lower and used a Solas 4 blade prop. On this boat the problem was the bracket what makes guessing installation hight more unreliable even if there is rule of thumb, but stern heavy boats with brackets have another (and change it after planing) angle where the water rises after lower transom edge and that makes it more tricky to guess the right hight. I had less problems with straight transom boats and there the general rule of av plate level with transom edge was mostly correct, but not always.
After that I learned on my Venture 34 with the jack plates that engine hight is not really sooo important as it believed by most of boaters, but it was a heavy 34ft CC, on smaller boats the depth may be more critical.

Chris

 

[Stevenwest]

Wondering if anyone has put SHARROW propellers on their Grady 330

they are $5,000 but say they can increase mpg at cruise by up to 30% , completely change cruising speed and reduce noise and engine wear and tear because running at lower rpm
I created a new thread asking for anyone out there who is using them

Sharrow Marine - The Propulsion Revolution is Here

The Sharrow Propeller™ offers a faster, quieter, and more fuel efficient ride through state-of-the-art design that is custom machined and fitted to every boat. Two-time award winner and the first major advancement in propeller technology since the 1830s.

sharrowmarine.com

 

[everwhom]

Hey a quick thought: are you certain you have 89+ octane gas in the tanks? The 300's require 89 whereas the 250's only need 87. The 300's will detune themselves if you use 87 octane...