dumb qustion???

[tcuda499]

I'm not new to boating but I am new to performance boats,I know what drives are and trim, but what is {trim the drives} for more speed or handling. I thought the drives should always be all the way down?

[Dr. Eagle]

Originally posted by tcuda499
I'm not new to boating but I am new to performance boats,I know what drives are and trim, but what is {trim the drives} for more speed or handling. I thought the drives should always be all the way down?
Stern drives are made to pivot up and down within a defined range to vector or "trim" the prop thrust up or down. This gives the ability to lose wetted surface for speed or to force the bow down while coming out of the hole.
Older OMC drives actually trimmed the entire motor/drive as a unit, but they did still have the ability to trim the boat.
Trim Tabs are another thing altogether...

[tcuda499]

Thanks,I understand a little better but out if the hole you would want the drives all the way down or in right?

[Dr. Eagle]

Originally posted by tcuda499
Thanks,I understand a little better but out if the hole you would want the drives all the way down or in right?
Yes, all the way down/in. As you pick up speed you bring the drive up a little at a time as the boat feels "set" properly. It takes a little bit of practice to get it smooth.

[tcuda499]

I got it now, I always thought that if the drives weren"t all the way in that you could damage something,hydrolics or something but I guess not. Then when would trim tabs come into play?

[mike37]

Originally posted by tcuda499
I got it now, I always thought that if the drives weren"t all the way in that you could damage something,hydrolics or something but I guess not. Then when would trim tabs come into play?
some of the old drive did not have power trim the drive
went up and down for traloring only so you needed to have the drive down wen runing

[tcuda499]

No this has power trim on the bravo drives and trim tabs. Are the tabs just for leveling the boat and also to keep the bow down or can they be used for turning and handling improvements?

[Dr. Eagle]

Originally posted by tcuda499
No this has power trim on the bravo drives and trim tabs. Are the tabs just for leveling the boat and also to keep the bow down or can they be used for turning and handling improvements?
The tabs can counter an off balance loading, help you get on plane, and help keep your boat from Chine Walking if it has that tendency... generally Vees with a high dead rise number will tend to do that depending on the hull design.

[tcuda499]

How do you know the bow rise number and whats high and whats low or a good number on a Vee?

[Dr. Eagle]

Originally posted by tcuda499
How do you know the bow rise number and whats high and whats low or a good number on a Vee?
Sorry, brain dead tonight... it's Dead Rise.
Generally the higher the dead rise number the better the boat will handle rough water. The dead rise is expressed in degrees as I recall... but like I said I'm brain dead after 18 holes in the heat today.
It is only one of the factors to look at in the hull design and it is taken into consideration depending on the waters you plan to boat on.