I have 1997 370DA and my battery setup is similar to Air O'Nautical's above, except I have two batteries in parallel for the port engine with five batteries total.
House loads run off of the two starboard batteries only.
Port batteries provide power to the port starter only and can be used to...
I go through the thru hull also - as seen in this youtube video: http://youtu.be/hDV1KFgwEKs
The only difference for me is that I connect a garden hose to my washdown faucet on the boat and use that as the source of pink anti-freeze. I also have a brass adapter from the garen hose to a 1/2...
I saw this guy down on Block Island back in late July... the boat definitely stood out in the mooring field. He had the Harbormaster visit him a couple of times - maybe he's from out-of-country.
The sync is correct... the tach that is not jumping around (port?) should be the true rpm indication. This problem is common - if you do a search you will get a lot of information.
You may have more than one problem... As mentioned above, new cap, rotor and wires and check the timing. A backfire through the exhaust is unburned fuel igniting in your exhaust system.
You may also need to rebuild the carb's... (hesitation issue). Just my $.02
Marina Bay in Quincy is the way to go... I kept my boat there for 7 years and enjoyed the restaurants and boardwalk area. They also have a lot of nice condo's for rent right in the development. And I believe there is a commuter boat into Boston from the marina also.
Good Luck in your move...
The only searays I see porpoise are one's with the I/O's... with the engines all the way back against the transom and the additional weight of the outdrives. I have not seen boats with straight inboards or V-drives have this problem. I would say the gap between I/O's and v-drives is greater...
I/O's are ass-heavy compared to straight inboards. With inboards, because the engines are located farther forward, they balance the boat off and ride better.