Minimum Planing Speed & tabs

[Sardinia306Canyon]

FA,
did you installed the DF200's or a dealer and can you remember if the you/they used the same hole as the Yamahas before.
If so, you should lower the engines one hole, on all boats i changed from Yamaha to Suzuki i had to lower one hole otherwise propeller ventilated too early. Lowering one hole does not affect performance or general behaviour negatively, but will avoid problems with ventilation.

You can hear ventilation when the sound of the engine changes, same as when you trim up too much, in both cases the propeller/s start to pierce the surface and suck air and that generate this particular sound.
When props start to ventilate rpm will get up but you loose traction and boat become slower.

Chris

 

[seasick]

As a follow up to my earlier comments on cupped blades, I did go aback to the reference book on props and it does state two things about cupper blades; The first is that cupped blades will increase the effective pitch by an inch or so but more importantly the reference states that cupped blades have virtually no effect below 30 knots.

The first statement could mean that that if low end performance improved with cupping the original prop's pitch was too small.

I got this info from the Propeller Handbook, by Dave Gerr. That book has more information than you would care to know and gets pretty deep into the mathematics and physics. If you tend to be an engineering 'geek' and like to understand what the dynamics of props are, you will enjoy the book.
If you are looking for a simple reference that tells you what prop you need, this book is probably not your best bet

 

[family affair]

Good to know. I'll take that up with the prop tuner.
I'd love to talk to someone who engineers props to better understand my experience. The inconsistency in performance depending on conditions and load is a head scratcher for me. Last weekend I ran 9 miles in a confused chop. I would have bet the farm that I would have traction issues based on my experience earlier in the year. I had zero issues all day.
Mounting height is the same as the Yamaha's. Some claim deeper with a Suzuki is the fix, others have said from their personal experience that it isn't always the case.

 

[Sardinia306Canyon]

Ken from Propgods suggested me added cup on the Powertechs i bought thru him to solve my ventilation problem thru sternheavy behaviour on my Venture 34, and they worked not well at all. AFAIK, added cup will give propeller more bite and let it suffer less ventilation.

Mounting height is the same as the Yamaha's. Some claim deeper with a Suzuki is the fix, others have said from their personal experience that it isn't always the case.

There is no 100% black or white on a boat and particularly not on propellers what once they are bolted on it becomes a fuzzy science as boat influence heavily how the propellers behave. Same for sea state, ventilation may does not show up on glassy sea and slow accelerating while ventilation show up on hard acceleration and/or choppy sea.
Regarding engine height, i installed 4 of my own Suzukis; 1 DF200 V6, one DF300 and twin DF300AP and on all i had to lower the engine/s one hole to get rid of ventilation issues. Same (but not on all) on some boats from the shipyard customers i worked for.

Your DF200 as all other at least 200HP+ Suzuki outboards should swing 16 inch wider propellers as that is why their gear ratio is designed for. This means that a 16 inch wide propeller is half of the diameter difference to a 15.xx wide propeller higher.
But i also believe that the hole hight between Suzuki and Yamaha are slightly different, Suzuki may be a tiny bit more higher as Yamaha and this together with the wider propeller diameter could lead to excessive ventilation on some hulls/weight distributions.

If our boat would be mine i would have lowered the engines one hole, if she sit on a trailer then it's not a big deal while when slipped then it probably becomes expensive as travel/forklift and renting a maintenance rack is involved.

I had Hydraulic Jack plates on my Venture 34 and could lower the engines about 2 holes too low
I did extensive testing and honestly there was no big difference between all down and max possible up, maybe a knot slower at WOT, but nor porpoising nor any other odd behaviour. This may apply only to Suzuki DF300AP because their particular designed lower unit and may be different with other shape lower units.

The inconsistency in performance depending on conditions and load is a head scratcher for me.

Well, both influence performance
glassy see not best for WOT Speed
1/2 ft short period wind chop best for WOT speed as a lot of air get under the hull
1 ft+ chop or waves are again bad for WOT speed

Same for weight, alone with 1/4 full tanks a planing boat is faster than in 4 with full tanks, ice and fishing gear.

With a lot of weight and moderate chop you may navigate better than light boat under same conditions and a frequently wildly underestimated problem is weight distribution on a boat, as smaller the boat as more important that becomes.

Chris

 

[family affair]

I have one hole left to go down with my engines, but I'm not sure if I can use it. It appears the transom might interfere with the engine bracket. I know there are 2 other islander owners on the forum with DF200s. I need to see what hole theirs are mounted on.

 

[Sardinia306Canyon]

Well, obviously if you can lower one hole what mostly works but sometimes the hydraulic piston hit the splash well wall and/or the outboard can be tilted up less as the cowling will hit something..
Chris

I know there are 2 other islander owners on the forum with DF200s. I need to see what hole theirs are mounted on.

Yes, thats the best source for first hand informations.

Chris