1999 SONIC 358 Drive Spacer Recomendation
 

I am going to install drive spacers in my 1999 SONIC 358 twin 550HP/500 HP rebuilt engines with bravo 1 drives and 28 pitch 4 blade bravo props turning inward. I am experiencing prop blowout getting on plane and bow hop once its on plane.

Has anyone installed drive spacers on a 358 to eliminate a similar problem? Should I go with 1", 2" 3" spacers?

Any help is appreciated.

Thanks, Tom

I don't own a Sonic, but have been researching them pretty hard. Seems most folks with the porpoising issue trade up to a 5 blade Hydromotive, same as the Nordic folks. In the Nordic world those things cure damn near every negative effect known to man. You could always try to measure your X-dimension and see if a spacer is truly needed. Not sure what the happy height for a 358 is. Maybe someone will chime in. Good luck either way!

Jay

How does the ride change if you spin props out?

Jay

You may be on to something with the 5 blade props. Tom

I switched the props so they were spinning out and it was still bow hopping.

Mine spin out.

I get the bow hop but it is super easy to tab into control.

It's the notched transom that is causing your porpoising issues. You may be able to cure it with prop tuning, but remember these boats were not designed for flat water. The 28 and 35/8 Sonics suffered the most from this, but none of the Sonic models were immune to it.

The notched transom puts the props in "cleaner" water when running in the rough stuff; which is what allows these heavy boats to carry the nose when needed.

Some folks have gone so far as to fill in the notched transom to run a true squared transom; when they run primarily flat water and have not been able to get the porpoise dialed out.