Lots of prop venting, help!

[SteuryLover]

Well I finally got the engine running right for the first time for anyone who has fallowed my other post on low RPM. Here is the issue now.

With a full load the prop gets little grip and vents bad. If im at 4500rpm and gun it, it will start to vent also. I really have to ease into it. Below are the details, any help with this would be great. Thanks.

18'4" center console deep V 1500lbs (hull+motor)
1993 Johnson 88 spl 15x13 3/4 SST OMC prop one hole from the top.
Loaded boat with fuel, gear and passengers approx 2600lbs

I do have a bait well pump mounted on the transom, it seems to make a large splash to interfere with the clean wake once planing. I also have a transom mount transducer but it barely interferes with the wake. The boat will eventually do approx 36 mpg via GPS at 5400k. I would like to be able to hit it and go. Right now it is a task to get the boat to grip up and go above 15mph. Gotta ease up on the throttle to do so. The ventilation plate is apprix 1" above the bottom of the rear of the keel. Thanks for everyone's help.

 

[Silvertip]

Re: Lots of prop venting, help!

Lower the engine one hole.

 

[SteuryLover]

Re: Lots of prop venting, help!

Will do tomorrow, or as soon as the rain stops.

 

[Silvertip]

Re: Lots of prop venting, help!

I just looked at your specs again and I see you have a 15" x 13P prop. That motor typically runs a 13-1/4 (give or take a bit depending on pitch). And 13P sounds like way to little pitch so you are getting blow out. The blade tips on the 15 inch prop are probably surfacing which may be causing the problem. See if you can borrow a 13-1/4 x 15P/17P and try that with the existing height adjustment.

 

[SteuryLover]

Re: Lots of prop venting, help!

Actually it is a 13 3/4"x15P OMC SST.

 

[Silvertip]

Re: Lots of prop venting, help!

Ok -- so then go back to my original response. Lower the engine one hole.

 

[SteuryLover]

Re: Lots of prop venting, help!

I should give a little more detail. The SSt was used, and now with closer inspection is worn pretty bad. I went a bought a 13 1/2" x 15P QL alum prop to see how it works. It grips ups great, I do not think the motor needs to be lowered. Although the new prop is working great I think I would like to send my SST to a prop shop to get reworked and the cup brought back. I think that was the problem. I will keep you updated on the progress.