Brett,
Regarding the diffusers effect on the boats attitude aside from planing, do you find that a diffuser adds stern lift to boats running negative and neutral trim? I think by lengthening the gear housing there is more surface to carry the stern. Do you find this to be true?

Hi Jim,

Absolutly the diffuser can create stern lift. THe closer the prop shaft is to the surface, the more it will be amplified. The gearcase and exhaust tube can become planing surfaces. Throw in a flared diffuser it can get worse. If you are able to surface a propeller on your rig, flared diff's should be removed.