please help a aussie

[hydrobuzzie]

hi there guys im just starting to race hydroplane in australia . , i bought plans off rick folick and have build one of his CHS boat , now i had to make the air trap a little width to help with my weight , i weight about 120 kgs or 250 pound i think , just would like some in put where to start with trim on the engine , which is a 25hp tohatsu , and what prop you think about using , thanks for any in put cheers jason :)

[Bunker Hill]

Well...
G'day! For starters, your height set up will be limited by the location of your water pick ups. So if there are no modifications done to the water pick up situation you will probably need to run deep, 5 cm or more beneath the bottom of the boat. If you have water pick up mods, then handling and planing issues will determine max height. In general you want to go higher to be able to pull a larger pitched propeller, that's "In general" handling issues will dictate a max height. As far as angle goes, place a straight edge lengthwise down the center of the bottom and make 2 measurements: first at a stationary front point on the gearcase (Cavitation plate for example) and a second measurement at the rear of the fixed position. You can adjust "Trim in " and "Trim out" from these points, you probably don't want to be too far out, probably no more than 7mm in the length of your cavitation plate, trimmed under will help you plane but may keep too much boat in the water, I would say to start at about level and adjust to suit your comfort zone. As far as propellers are concerned, contact Ron Hill of this site, he has vast experience with this type of engine, he may even have prop(S) in stock, I am guessing that a good "SHort Course" sport C propeller may be the ticket!!
Good Luck, Welcome aboard

Cheers,

Bunker

[Skoontz]

You basically have 3 choices.

First, install a nosecone on the stock gear foot that has water pickups on the bottom of the point, then connect a hose off that to your stock water intake tube somewhere.

Second, install a small clam shell pickup behind the propeller where it will be throwing water.

Third, check to see if there is any hollow space in the stock casting between the forward bearing and the outer case. If there is, and it is sealed off, you might be able to drill it and place fittings on top where there is no water contact.

I guess there is a fourth, buy a race gearfoot from one of the manufacturers with a similar HP and displacement, but, that one's gunna cost the most.

You have a funn looking boat!

[hydrobuzzie]

thank you Bunker HILL and Skoontz , your inforation has been very helpful , i have made a fibreglass nose cone .. to make it more bullet shaped with scoping up to the water pick ups , would love to run a quick foot , but not allow in our class as the engine has to be stock just allow to change propellers and timing and nose cones , and that pretty much it . as for the bullet on the gear box its about 50mm under the transom and was think of running a cleaver style prop ? again thank you all for the information and if any one has any more that would be great , happy boat racing to all cheers jason :)

[Bunker Hill]

There is a new post today titled something to the effect of "Small hatsu props" This seems to me to be JUST what you are looking for!!
Good Luck!!
Bunker