Congrats on the new ride! what engine did you have installed on this welded al. boat?
The "amount" of antannae is dependant upon your boating and area conditions.
Going offshore 20 miles+? Get a min. of a quality 8' whip mounted high
Going offshore 1-2 miles only? 4-5' quality whip maybe fine.
I recommend either ICOM or Std Horizon.
i haven't checked today, but there is a member selling white ICOM ?602's? for about $280 which is a steal! see misc. sell forum.
Remember that majority of the time reception/transmission voice quality is an antannae issue, so don't scimp and look to save $ here, get a high quality whip.
Also check out
www.pacificaerials.com. on their website they have a pdf file "more info." that goes over whip height, gain, etc. that may help clarify what you need. also i bought their 8' whip and switched fr. a similar shake's galaxy whip so i can be able to easily disconnect and remove the antanna (might be a good option for you if you decide to mount the whip on the hard half top)