Reducing planing speed

[headdamage]

I find that my H440 likes to travel at speeds of 30 kph and up to stay on plane. Displacement speed is around 10 kph and is wet in bad weather but 30 kph is too fast and rough. I've added hydrofoils to the motor and this helped but not a lot.

I run a Turning Point Hustler 3 blade prop, would a 4 blade help the H440 plane at a lower speed. Would adjusting the motor mount so that I can trim down lower help? I would like to be able to plane at around 20 kph.

Motor is a 60 hp OMC 3 cylinder 1993.

[paintman]

What WOT rpm are you getting with your current prop with the boat normally loaded and is it within the WOT rpm range specified by your engine manufacturer? Please post the figures.
Is the engine at the right height & correct shaft length?
Is the load in the boat evenly distributed or is there a lot of weight at the back? Have you tried sitting further forward?

[headdamage]

Normal load and with moderate trim I'm getting a WOT rpm of 5000. If I trim it right up to the point of the boat getting very light in the water/bow happy it just reached 5400 rpm. WOT should be a max of 6000 rpm with this motor. Current prop is a Hustler three blade 13.25 x 17, I do have a three bladed 13.5 x 15 OMC prop that I'll try to see if that does anything before buying any more props.

[jyasaki]

Do you have a lot of weight towards the back of the boat? Moving weight forward will help keep the stern from sinking back into the hole as you slow.

Other than that, perhaps some trim tabs to keep the back end up?

FWIW, my boat hops up onto plane about the same speed as yours.

jky

[headdamage]

Due to the lay out of the boat with a jockey console and very limited floor space there is not much I can do with weight distribution though I would say it is a bit stern heavy at rest.

[headdamage]

Finally got around to trying the 13.5x15 prop yesterday, WOT rpm trimmed right up was 5800 rpm. Min planing speed was around 29kph, top speed was 5kph slower than with the 17 pitch.