Increasing Performance 30Hp Suzuki

[Blackened]

G'day
The cowel is the cover for the engine. The bit on top you take off to get at the powerhead. I think what spudie is getting at is the top of the engine(cowel) should be parralel with the water in which you're traveling at planing speed. This will have the engine at the right angle with regards to trim positions. In theory the anti cavitation plate should be level with the water surface, sitting just under it and the trim angle will adjust the angle of the boat in the water, negative trim willb ring the bow down and increae friction with more hull in the water and positive trim will bring bow up, less friction and less hull in the water. You aim is to find a happy meduim. The anti cavitation plate should be level with the bottom of your keel (there abouts) as anything but will cause excess drag. You will need to raise this engine further still. Does it have the right length shaft or should you really have a shorter shaft engine on this boat?
Dave

[spudie]

thats it

[rojac]

The set up diagram in the motor manual recomends that the cav plate is 25mm under the bottom of the boat.

If the boat is designed for a ls motor and all(?) the ls are 508mm, then it may be that the leg is too long or the transom is too short. Maybe one of the components are the incorrect length otherwise it doesn't seem to make much sense.

Surely the manufacturer wouldn't design a hull that cant be set up.

[spudie]

the problem is that most of the dealers are just sales people nothin else.

[Seahorse]

i got 30hp merc on my 4.2m. i moved it out to 3rd hole from transom. made steering a lot lighter, but i notice water coming up from behind transom like a bubbling spa bath with the jets turned up, but nothing in boat. i got my hand held gps out that i dont yet know how to use and the speed said 32k on a flat day. i thought that would be klms? 32knots sound to fast. i had foil on but lost top end speed. top of cowell is dead level when travelling.

cheers
greg

[robersl]

i also have a 30 hp suzuki i find it gets along ok but in saying that the leg does sit a lot lower in the water than my yamaha 40 used to even when the motor is tilted i find at the ramps i have to have the back of the boat out further before i can drop the motor to tilt and start it the motor has been lifted by the dealer onto a plastic block on the transom and will not be able to come uo much more either the trouble i had was the boat pulling to 1 side so i had to adjust the anode above the prop

shane

[Blackened]

g'day
Greg, at a rough guess i'd seriously imagine you'd be gdoing 32kph, not knotts. Reasoning is i have a 12' tinny, 9.9 merc and flat strap it does 35kph (about 20kts). The power to weight ratio would be somewat similar i'd imagine,
Dave

[Roughasguts]

Hi Tinn, Think you got two choices here.

As said before raise transom height all you need is a rectangular section of aluminium same thickness as the top of your transom, looks like you may need around 70mm gain in height.

Anyway then some alloy plate comming down both side of your transom welded to that rectangular section and put some long through bolts through it all to clamp it nice and tight to your existing transom.

And of course fill the old bolt holes.

That be the best option.

Then theres those foils that will help lift the arse of the boat up and out of the water and get the bow down that will increace your speed.

But really that be the band aid solution and I'm not a beleiver in foils to any great extent. They will change the handling of your boat and can give you a bit of a fright until your used to it. But still there a cheap fix and work well if you have a lot of weight in the back.

[7dan7]

I had a 3.75 allycraft + put a 15hp yammie behind it + had the spray problem the transom needed another 60mm. i got piece welded in + fixed problem. motor is definitely to low if you are getting spray.

cheers dan

[Tinn]

Okay guys looks like I will have to build up the transom. Anyone know of a good place to get the welding done?

[spudie]

iwhere are you

[Tinn]

My boat is located at eight mile plains brisbane. Must fix this spraying problem. I think it will probably go alot faster if it is setup right

[billfisher]

I don't think foils will help top speed. At full throttle they just create drag and you will lose a knot or two. They are good for getting on the plane quicker and maintaning plane at low speed.

[Tinn]

I won't be fitting a foil. They slow down your top speed. Will be lifting the motor tho so I can stop the spraying and try to get the top revs out of the engine. Maybe even getting a different prop will see what revs I get once I lift the motor up

[ahoj]

-----If your motor runs at full bore and you take the eccelerator slowly down without reducing speed of your boat to say 70%-- then your motor is overloaded and can not push your rig to full speed-- reducing your impeller's pitch down will make your motor reach top revs and the boat speed will be relatively the same as before( perhaps marginally faster)
If you increase the pitch you will overload your motor and perhaps only run at 3000 rpmand you will delete your motor soon

Load and load distribution can help your boat to get up Your boat should do around 45Km/h with 30 Hp. There is a posibility that your max rev screw needs adjustment. check your filters-- air and Fuel and timing compression test will help you to discover that you may have a problen somwhere else...

Ahoj