samin 0 Posted May 11, 2011 Share Posted May 11, 2011 Does anyone have any tips for how high an outboard bracket can be for the motor to not cavitate in a steep chop? my new 8.5m tri has no bracket, and I was planning to have the 8hp transom hung of the back step of the cockpit (main hull) which will mean the cavitation plate on the motor will be about 50mm below the waterline when motoring I am worried it will cause problems but I dont want to have a bracket on the stern....? Link to post Share on other sites
Guest Posted May 11, 2011 Share Posted May 11, 2011 I'm no expert but I do know that when my long shaft is in the well we have zero dramas. When I have the short shaft in I get some, especially if big throttle is applied but little or no boat moving at the time. The short shaft cavitation plate is deeper in than 50mm, guessing 150mm odd. So I'd expect 50mm isn't deep enough, as I'm sure your missus would agree I don't know but would one of those wider clip/screw on cavitation plate thingys help??? Link to post Share on other sites
Atom Ant 0 Posted May 11, 2011 Share Posted May 11, 2011 Samin, I'm no expert on outboard placement on multi's but having had one on my SR, I'd say that no matter what the boat you need to ensure that the prop doesn't pop out of the water in a biggish sea, or when someone goes forward to deploy or pull up the anchor. Link to post Share on other sites
samin 0 Posted May 11, 2011 Author Share Posted May 11, 2011 AA have you got any idea how deep the prop is when the motor is down? have you got any photos? Link to post Share on other sites
Marshy 30 Posted May 11, 2011 Share Posted May 11, 2011 Last saturday was the first time my outboard has ever come out of the water Sam, motoring side on to quite a swell with motor off to one side, so that wont happen in a multi. Not sure how deep the motor is in the water though, WOuld have to measure it, which i can do on friday for ya, can hapilly walk to bow and drop anchor without worrying. The other thing to think about is do you want to motor sail? Prob not such an issue on the tri i suppose? Lucifers doesnt seem quite far enough into the water as it cavitated a fair bit on the way to BMW race track that weekend? Link to post Share on other sites
Atom Ant 0 Posted May 11, 2011 Share Posted May 11, 2011 I'll have a look for photos, it's been 8 years since I owned it! Link to post Share on other sites
rigger 47 Posted May 12, 2011 Share Posted May 12, 2011 On my old boat I had an adjustable bracket - allowed a little bit for when motor sailing - longshaft yamaha - good value. cavitation place was at least 100mm down in the water Link to post Share on other sites
Guest Posted May 12, 2011 Share Posted May 12, 2011 On the R830 I race on the cavitation plate would be at least 400mm down. It is in a well though. It sticks out the bottom of the boat as much as a saildrive, but lifts out for sailing. Link to post Share on other sites
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