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Author Topic:   13-foot hull: Engine cavitation in turns
Cabane posted 05-06-2003 10:13 AM ET (US)   Profile for Cabane   Send Email to Cabane  
I had my first outing in my 1971 13-foot Whaler with Evinrude 40-HP and stick steering [Note: the author does not mean steering with an engine mounted tiller, but instead refers to an unusual forward console arrangment with a side mounted steering arm mechanism. See a photo of his boat in the hyperlink below--Moderator.] The boat cavitates on less than gentle turns at speed. Is this common with these hulls?
GeneNJ posted 05-06-2003 07:43 PM ET (US)     Profile for GeneNJ  Send Email to GeneNJ     
Boats with hard chines tend to raise one side when in a turn, lifting the prop. Can you lower the motor further? I had a Proline that did the same thing, only way around it was to keep the bow down from its normal position. With power trim it was an OK workaround as the dealer/factory had no other solution.
Cabane posted 05-07-2003 10:38 PM ET (US)     Profile for Cabane  Send Email to Cabane     
Thanks for the reply GeneNJ. The motor is in the lowest trim stop and the bow rides a little higher than the stern on plane. It's a short shaft Evinrude. I haven't checked the prop pitch and dia but I suspect it's the 'OEM'. It's in good shape no dings dents or gouges. It seems the boat side slips and the prop doesn't bite. I hear an audible rpm change not a over-rev decoupling... if this makes ant sense. I'll try a different motor trim position.


Cabane posted 05-07-2003 10:40 PM ET (US)     Profile for Cabane  Send Email to Cabane     
Here's a rear view.


jimh posted 05-07-2003 10:54 PM ET (US)     Profile for jimh  Send Email to jimh     
[Changed TOPIC; was "13...cavitates in turns"--jimh. Also, added comments about steering position.]
lhg posted 05-08-2003 03:45 PM ET (US)     Profile for lhg    
Just to be technically correct, this subject is ventilation (air being drawn into prop) rather than cavitation, which results from damaged props.
Cabane posted 05-08-2003 11:35 PM ET (US)     Profile for Cabane  Send Email to Cabane     
Yes maybe sucking air. This configuration may lend itself to this condition...? It is very responsive. May be the nature of the beast. Hence my query.

captbone posted 05-09-2003 12:17 AM ET (US)     Profile for captbone  Send Email to captbone     
I sued to run my whaler with the fuel in the front. I would try doing the opposite and try and get as much weight in the stern as possible. This way it will be lower and wont come up in the turns,
captbone posted 05-09-2003 12:18 AM ET (US)     Profile for captbone  Send Email to captbone     
I used to run....... not sued
Gep posted 05-09-2003 12:28 PM ET (US)     Profile for Gep  Send Email to Gep     
Are sitting in the front seat? Maybe you have too much weight forward like Captbone says.
How does the steering handle with that stick?
Is it kind of awkward to get to the throttle?
where2 posted 05-09-2003 12:48 PM ET (US)     Profile for where2  Send Email to where2     
Steers just like an Air Boat! I'd take the prop off and carry it to a prop shop and have them cup it. I had to do this to my 9.5hp Evinrude on my Zodiac years ago. With cupping on the prop, it was nearly impossible to get it to ventilate/cavitate. It's amazing what a little lip edge on the trailing end of the prop blade can do to help these problems.
Bigshot posted 05-09-2003 04:28 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
With the Trophy you sit on the front twart so stern is way light. those old engines cavitate REAl easy so try cupping the prop like where2 said. My 1982 did the same thing even with weight aft, especially in following seas.

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