Re: chrysler 140hp help australia




Serious question. Do you fellows have regulation as to how much horsepower a hull can carry? The reason I ask is because I have seen a number of your hulls which are very small, yet there are big engines on them.
Down to business: Your engine appears to be mounted at the correct height. It is normal to ventilate (you call it cavitation), sometimes quite a bit, in turns, especially if you do not or can not trim the engine down. She makes a lot of noise, revs higher, and the boat slows. Then, when you complete the turn, she locks up again and takes off. Ventilation and cavitation are two different things but ventilation can lead to cavitation.
Now, I see you also have the very old style prop. Back in the late 1970s when Chrysler first designed the one piece lower unit, this was the stock prop and a tailcone was included. Unfortunately, The one piece was designed one inch shorter than the old two piece in an effort to reduce drag and gain some speed. Indeed, the one piece lower unit IS and was about 3 MPH faster than the two piece. HOWEVER, customers complained bitterly because the engines ventilated and cavitated too easily. SO, Chrysler rushed into design and production the "Anti-cavitation" flare washer (Shown with a tailcone in the first photo). This did help some.
SO, in an effort to gain more speed:
1. Remove the wing if the hull does not need it. It is extra drag. Of course, this may cause problem yanking a person out of the water. The hull may go bow high. You need to prioritize here.
2.Change the prop to a newer style and if it is a closed hub prop, use the flare washer and tailcone. Second photo shows the difference between an open hub and closed hub prop. You CAN use a flare washer on some, but not all open hub props.
3. Stay with stainless steel props. Generally, in the same design and pitch, they run about 200 RPM faster. Experiment with aluminum because they are cheaper. Then, when you find the sweet one, go to stainless.
4. lastly, as I said before, keep an open mind about props. You can use many Mercury props AND many other props can be re-hubbed to fit Chrysler propshafts. see next post for photos of re-hubbing at home.