Just tested again, took the dolphin off kept the engine height at 5 inches, drove much better, steering felt great, top speed at 5k was 50. Raised the motor one inch, water pressure good, steering good, gained 5 MPH and Wot is now 5500, may raise some more. Still have to tuck the engine fully to keep from porposing under 30 MPH, this is ok. I'm using the hustler 19 four blade. Also upon getting on plane tack reads 4k, does this sound right? Next question: my SS turbo 3 blade with 1/4 inch vents is a dog out of the hole, would you suggest drilling to 3/8 ? I figure I can always plug them. Once again I thanks you all for your help.
Moving right along. As I said before porposing is caused by improper boat/water/engine thrust relationships for the speed. When I mentioned getting OVER the porpoising curve you are experiencing what I said at the slower speed.....you are below the curve, porpoising, so you have to change something if you want to stop it. On my boat I tuck in the trim till it stops, unless I want to speed up and get on the other side.
Your 4k in the hole is probably your ports doing what they are designed to do and a good number if it occurs as the bow is coming back down from the shot: They allow the engine to unload in the critical hole where stresses on the engine are max. Allowing it to unload by running a mixture of gas and water over the blades and reducing the density of the medium lets the rpms come up which bring up the hp and hp turns the prop and gets you out of the hole; the faster you can "get em up" the faster the hole shot.
On port size, "size matters". Too large and that 4k may get to 5k and long hole shot with engine revving. Too small and might as well not have them.
I think 3/8 is a great number if it's right for your application. With your 4k at the end of the hole (assume that's where you get it) I think you are where you need to be. If working correctly, once you get underway, pressure of the water running by the prop will seal off the ports solidifying the medium across the blades, loading the engine causing a very abrupt decrease in rpms (500 to 1k sort of thing) and increase in speed. You should be able to detect this. On my Ranger, it was very noticeable and I used to get a kick out of waiting for it to switch.
Your 50 at 5k is a super number. Keep tweaking it and you may get on up to 5500 and 55 mph which is where my son's 150 ran on his 17.5 (18) ProCraft. Engine is rated for 5600 and you want to run at-near-slightly above (I do).
On water pressure, your OT alarm switch closes at 195F so it you get too high and have no other way of knowing that you are running out of cooling water it will tell you. For a reference, my 2011 Silverado runs at 210 for the normal operating temp; so 195 isn't all that hot. A water pressure gauge would help and you should have a 1/8 pipe (plugged with a brass plug) on the right (starboard) bank water jacket. I think around 10 psig or so it what is expected at the higher rpms.
Mark
