North Australian FISH FINDER TM forums

I have issues with the holeshot ... or accelerating when the boat is on the plane, since the lower leg and hydrofoil was replaced by a workshop.

The lower leg was damaged when the boat was transported from Townsville to here.

In Townsville I could always trust the boat and the holeshot when coming back from the reef with following sea.

Now it seems that the prop doesn't always "bite" properly .... sort of like revving and not biting ..... as if out of the water.

I have noticed that the anti ventilation plate is about 5.5 cm above the keel of the boat.
Might it help if I drop the engine a hole or two to get the engine further into the water, keeping in mind that the boat sits very low in the water at the back (fibreglass boat, 120 liter of fuel under floor at the back and heavy 2stroke)

I can get it on the plane and it does about 65 km/h at WOT.

Cheers and thanks for any answers ... thoughts ....

Tim

Dropping it a hole sounds like it will help, you will lose a bit of WOT but probably get better "grip" in other situations.

Sounds like the rubber hub insert might be knackered and the shaft is spinning inside the prop?.........What damage was done and was the prop welded/repaired replaced etc?

When they did the repair did the prop get changed ?
Or did they move the motor,,the cave plate does look a bit high.
All set ups vary but reckon it should sit level with the keel.
If its sitting out of the water At WOT ,yes drop it.

Also check the prop bush .

Cheers

No mate, the leg was cracked and got replaced completely. The prop never had any damage and was never exchanged.

The hydrofoil is completely different though and that will make a change to what I'm used to.

Which rubber hub insert are you talking about?

The prop only does it in certain situations .... acceleration from 0 to 64 isn't bad .... the issues come when I start playing with the trim and the engine isn't fully submerged.

I don't think they moved the engine up .... Just the lower leg was exchanged. I've been trying to figure out if mercury built different length lower legs, but it seems as if the only extensions they put in, is done with an additional spacer.

pops70,, goggle propellerhub.com you'll find heaps of info that may answer
your problem

Try it without the foil mate , you say its not the same as the one you had b4 the misshap, foils lift the bum of the boat up and if your motor was a bit high anyway, and bigger foil will make it even worse, but as a rule the cav plate ,wich will have the foil bolted to it must be level to the hull or slightly lower, other wise it will slip just like if your clutch was buggered in your car..

Ensure any holes left from the foil mounting are filled too....

We recently had to put prop guards on our boat for a job...

After we were done we removed the guards, this left 4 x 6mm holes in the
Cavitation plates.

Those four 6mm holes was enough to suck in air and stop twin 300hp motors getting us on the plane.
Took it back, epoxied the holes and it was right as rain again. Doesn't take much to cause cavitation!!

the red line you have put on the second photo is not the plate you want lined up with the transom, the one you want lined up with the transom or 10 mm higher is the cavitation plate that the hydrofoil is bolted too. when you are on the plane keep in mind the water rises approx 25mm for every 300 mm you go back.