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Author Topic:   Skiff porpoises
NausetBoy posted 05-13-2003 09:25 PM ET (US)   Profile for NausetBoy   Send Email to NausetBoy  
I have a 15 ft wooden skiff with a 25hp Yamaha four stroke. It porpoises badly at high speeds. Gas tank is located in the middle. No room up front. It is tiller operated and AV plate is even with keel. What can I do? Please help
Sal DiMercurio posted 05-13-2003 09:53 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Your engine is to low, raise it up another inch or 2, as long as it dosen't break loose [ cavitate or vent ], your fine.
JBCornwell posted 05-14-2003 12:48 AM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Don't agree.

Reduce the trim-out, even if you have to use wedges to do it.

Red sky at night. . .

Sal DiMercurio posted 05-14-2003 01:22 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
I assumed he's already tucked in all the way.
NausetBoy posted 05-14-2003 07:49 AM ET (US)     Profile for NausetBoy  Send Email to NausetBoy     
Its down all the way, and still does it. Would a hydrofoil work?
hooter posted 05-14-2003 08:49 AM ET (US)     Profile for hooter    
Doel Fins will prob'ly cure the problem, but Ah'm with Sal. If a pair o' easy $20 fins still leave you doin' the Flipper thing (which Ah doubt they will), and if you're trimmed all the way in and the cav'tation plate is on plane with the keel, then you're last option is t'remove that engine and shim it out at the top to get another inch or so of "in" trim. Don't think Ah'd raise the cav'tation plate above the keel, if that's where JB was headed.
Florida15 posted 05-14-2003 09:29 AM ET (US)     Profile for Florida15  Send Email to Florida15     
I had an '85 Mckee Craft that did the same thing - porpoised at higher speeds. I called the factory and they recommended mount the motor on wedges to get the foot in closer to the boat. It worked.
NausetBoy posted 05-14-2003 04:28 PM ET (US)     Profile for NausetBoy  Send Email to NausetBoy     
Oh yea this engine is not bolted.
Sal DiMercurio posted 05-14-2003 10:13 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
You might be better off bolting the engine, that way you can raise it as high as you want.
I'm sure a dole fin will work, but it will also force the bow down when you really don't want it down that flat.
In rough weather yopur going to want the bow to be up, but it's possible a fin could force it down resulting in a very rough ride, as every way you will pound your brains out.
NausetBoy posted 05-15-2003 07:22 AM ET (US)     Profile for NausetBoy  Send Email to NausetBoy     
Thanks Sal. I live on a river where it is not rough often. So it probably wont be a problem. I am thinking of bolting it on at a later date. Thanks!

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