150 Johnson, HS bass boat, prop to pad

[fishdady]

Not sure if this is where to ask this, but, I have a 1980 150 hp Johnnie on the back of a 1985 Hydra Sport x270. Blew a 140, and replaced it with the 150. Now I have a porpoising problem. I'm thinking I have the engine to low. I used the same holes, on the mount as the 140. I did notice the skeg hit the garage floor sooner then it did with the 140. Anyways, I don't have a jackplate, but, have found a starting point, with a jackplate is 3 1/2 in. prop to pad. Is this true without a jackplate? Yes, the 140 and 150 are both short shafts. Thanks in advance, Fishdady

 

[gm280]

Not exactly understanding your 3 1/2 inch prop to pad statement. Check to see if your cavitation plate on the OB is even with the bottom of the hull and make that your starting place to see how it works. That will be the baseline for all other changes. A manual jack plate would be really nice to make such changes without redrilling and sealing old holes in the transom. I had a problem on my Bass Boat with the engine sitting too low and when I installed a manual jack plate and raise the engine, wow that boat came to life... Just a suggestion...

 

[fishdady]

Thanks for the response and advice. Jack plate is definitely on my wish list. Just never had this problem with the 140. After I come off plan, it starts porpoising so bad I have to idle down to get it to stop. It looked to me the LU was down further then the 140 was. Most setup forums I've read, says, set at 3 1/2 in. below pad as a starting point and adjust jackplate from there. That's where the 3 1/2 came from (scream and fly, bassboatcentral set-up boards) The S/S prop,that came on the 150, was junk. replaced it with a turning point aluminum 14 1/4 23 pitch. running 53 @ 5400 rpm @ WOT. Sorry, I'm on a budget (retired) and just a work in progress. Thanks again, Fishdady

 

[SkiDad]

maybe just raise it up 1 hole - that is probably the 3/4 of an inch you may have dropped ??

 

[fishdady]

Going to try it, got a base gasket to replace, good time to move it up, Thanks, Fishdady