Blowout due to shorter bullet?
 

Saw on another thread that the pre-1990 Bravo drives have a shorter bullet than the later drives and it can cause "blowout" somewhere north of 70 mph.

Can someone explain what that is and what the symptoms are? I'm fighting a handling issue that starts at 70+ mph.

The older lower is not as hydrodynamic and will disturb the water more as it passes around the bullet. This will cause some aeration of the water and the prop will slip more.

Thx Griff

I'm not seeing/hearing the RPMs jump up, so wondering if it's a more of a subtle slip effect. Maybe just enough increased slip to lose some stern lift and get a porposing event started? I'm climbing onto the pad when all this starts (simultanious chine-walk and proposing).

Are there nose cones that can be installed temporarily to see if it helps??

I really don't know for sure.
I suppose you could epoxy a nose cone on without doing the finish work, but that may still disturb the water flow.

Is this a totally new set up or boat??? Or what has changed?? What boat and prop and have you tested some different props??

Hydro-Motive sells a decent nose cone that I have used with success. You need to do some serious blending to avoid creating a bigger problem. I used a piece of stiff wire to check the radius from the point to the body of the bullet and used a good metal epoxy as filler where needed. You need to make sure the point is dead center as well. I ended up sanding the nose cone to shape it exactly how I wanted it. In the end it looks stock and works great.

What prop are you using? Might be able to lab or add cup or go up a blade or go from a 3 to 4 blade or change what type and fix all your problems...

Boat is a 1990 Fountain 27/29. Abt 500hp per side. Props are Mirage 3 blades but have been work over by a friend of the prev owner of the boat. The guy that did the prop work passed away many years ago. I dont know his name but he was real popular in the Hou area many years ago. I have 2 more sets of Mirage props that are supposed to be the "salt props". Not sure what's different abt them or if they are modified or not. I've never tried them since I'm fresh water only.

I thought my high speed stability issues were due to having internal steering. After switching to full hyd ext steering and replacing all the bushings/seals for the drives, I still have the same high speed handling issue. Outdrives have zero slop now when attempting to manually move them up/down or side to side.

What was the orig issue that made install the nose cones?
Just looking for speed or was there another reason?

Borrow a set of 4 blade Bravo One's or try the other set of Mirage Plus.

Most likely done by Darin at Houston Propeller. He did a prop for me way back when and was on OSO.

I would test the other props you have and test a set Bravo props.