Donzi 27ZX Porpoise problem
04-03-2020, 09:56 AM
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Donzi 27ZX Porpoise problem
Hey guys,
I have a 97 Donzi 27ZX with the stepped hull. It currently has a 555 with a blower pushing 740hp and an XZ drive with a 28p 4 blade. The boat starts to porpoise at around 72-73mph. The previous owner put some giant trim tabs on it to fix the problem. It takes some playing, but it eventually does work. He then went on some forums and was told that this particular hull raises out of the water another 2-3 inches at that speed, causing the prop to surface, creating the porpoise. So a drive spacer should eliminate the problem. Any thoughts on this? Also, how does one find the proper X dimension for this hull? I would assume every hull would have its own sweet spot?
I have a 97 Donzi 27ZX with the stepped hull. It currently has a 555 with a blower pushing 740hp and an XZ drive with a 28p 4 blade. The boat starts to porpoise at around 72-73mph. The previous owner put some giant trim tabs on it to fix the problem. It takes some playing, but it eventually does work. He then went on some forums and was told that this particular hull raises out of the water another 2-3 inches at that speed, causing the prop to surface, creating the porpoise. So a drive spacer should eliminate the problem. Any thoughts on this? Also, how does one find the proper X dimension for this hull? I would assume every hull would have its own sweet spot?
Last edited by Upnorthdonzi; 04-03-2020 at 10:00 AM. Reason: Better title
04-06-2020, 07:21 AM
#2
Dont have any 27zx experience, but in general, some additional info would be helpful. What specific prop are you running? Have you tried different props? Porpoise starts at 72 and goes to what speed? Continues all the way to top end? At what trim setting does this occur? Once it starts it continues through all trim settings?
