smart tabs on a heavy boat

[KeyWest225]

Looks like I stumbled across the right post! I too am having problems with porpoising. I have a 23 deep V with a 225 Verado. That's a lot of weight in the stern, not to mention my batteries are also mounted back there too. I have the Lenco tabs. I have been searching all over the web, including the forums and have learned different techniques to deal with it but the one that most intrigues me is worth bringing up here. Although tabbing the bow down helps, the boat still wants to porpoise. Somebody suggested that my prop is too far below the waterline - ie my engine is mounted too low. I checked and there are 3 other holes on the bracket that will allow the engine to be raised. I am thinking this is my next step. Anybody know more about this than I do? Thx

[Roger]

Originally Posted by KeyWest225

Although tabbing the bow down helps, the boat still wants to porpoise. Somebody suggested that my prop is too far below the waterline - ie my engine is mounted too low.

That's been my experience - outboard too low. With the engine in neutral trim, you should barely need any tabs, or none, to avoid porpoising in flat water.

With an IO, engine height is not an option - obviously. They're left with motor trim, trim tabs, prop selection, etc as the alternatives.

[thunder]

the trim tabs work great but now i'm thinking about the prop,it says 5052-17 on the side,i cant even find it on the web it's a s/s prop the rpm and speed is close the motor does'nt overrev but with a 350 i think it should have some more get up and go

[Roger]

Originally Posted by thunder

the trim tabs work great but now i'm thinking about the prop,it says 5052-17 on the side,i cant even find it on the web it's a s/s prop the rpm and speed is close the motor does'nt overrev but with a 350 i think it should have some more get up and go

Huh? Close to what?

[Slipknot]

Originally Posted by KeyWest225

Looks like I stumbled across the right post! I too am having problems with porpoising. I have a 23 deep V with a 225 Verado. That's a lot of weight in the stern, not to mention my batteries are also mounted back there too. I have the Lenco tabs. I have been searching all over the web, including the forums and have learned different techniques to deal with it but the one that most intrigues me is worth bringing up here. Although tabbing the bow down helps, the boat still wants to porpoise. Somebody suggested that my prop is too far below the waterline - ie my engine is mounted too low. I checked and there are 3 other holes on the bracket that will allow the engine to be raised. I am thinking this is my next step. Anybody know more about this than I do? Thx

I don't know any more about that issue than you, but it sounds logical. And I think I will raise my 9.9 honda on my skiff up an inch since I get porpoising also. I look at the motor and the fins just above the water inlets is about an inch + below the lowest point of the hull on my skiff. Also I don't believe it is sitting 90 degrees to the plane of the hull so I might need a slight wedge also.
I am gonna give this a try before next time I go out.

[macojoe]

Are you guys running a tac?? If you are reaching the WOT RPMs from the motors company then you are fine, if you are to low or high tghen you need to get the right prop!
If no tac then get one!

[numbskull]

Originally Posted by macojoe

Are you guys running a tac?? If you are reaching the WOT RPMs from the motors company then you are fine, if you are to low or high tghen you need to get the right prop!
If no tac then get one!

Not exactly. His problem is prop pitch. A lower pitch and larger diameter would give him more bite at low rpm, but similar top rpm numbers. His top end performance (ie speed and fuel efficiency) would suffer SLIGHTLY......but his boat would run better and plane more easily. Being able to remain on plane at lower speed and higher bow trim is a HUGE advantage when the going gets tough....and well worth giving up a little high end performance unless you plan to cover very long ranges at very high speeds on very nice days only.

[macojoe]

I had much the same issue with my V20, I had a 15 x 15 1/2 prop and it worked great for the heavy loads I use to have, much of the other V20's have 17 pitch. I also had Hydrofoil and no tabs

Good Luck