mightyraydawg

US:
I've been a gearhead since 1964, but I'm relatively new to boats. My brother has owned several drag boats over the years, but this is his first offshore rig. He's made the carefully calculated error of including me in this engineering excersize in Fluid Dynamics, now I am including all of you as well.

THE BOAT:
My brother just got this boat wth a big, fast low-hour 588 Merlin-block motor in an OffShore rig, but sees only occasional use above 3-to-4-thousand on the tach. Full-throttle is no stranger, but is usually only used for 10-15 seconds at a time or until all the JetSki's are blown up onto the banks; whichever comes first. I realize we're, essentially driving a Ferarri in a Christmas parade, but the Merlin should work a little better than it's currently doing.

THE ISSUES:
Low oil temp, low coolant temp, carburetion is rich, plugs black (w-occasional fouling), oil gets black, etc.. I know what to do for each of these, as well as how to do it. But this is a boat, not a car, and there are caveats and dangers... hence, my joining and posting to this forum. We need some expertise so we don't take a giant poop in my brother's very expensive nest.

BY-THE-GAUGES:
Built to survive tortuous, full-throttle marathons, this monster runs TOO COOL in normal use. Coolant consists of that secret upstate blend of South Carolina lake water and catfish doo-doo, and the coolant temp runs down around 100-degrees. The external cog-belt driven H2O pump drives coolant pressure to around 6 PSI in normal use. Also, oil temp is LOW, much lower than I'd like to see it, and the oil gets dark quicker than I'd like. I know half this rant is about carb jetting, but I think we'd be way ahead of the game if we could wrestle a THERMOSTAT into the Merlin II and stabilize the coolant temp before we go hacking about in the carb.. Maintaining a reasonable coolant temp would allow the carb jetting (giant Dominator) to be made crisper, and likely fix the dirty oil issue while lowering fuel consumption to boot. It'd be win-win all around, but for (insert dramatic pause here) The Problem...

THE PROBLEM:
While a standard GM thermostat would fit right into the dual-outlet coolant neck on the top/front of the engine, it appears to me that ALL water to the header boxes comes through this two-pronged neck, and is Y-ed off with one line to each bank's header box. And while the thermostat would GREATLY restrict the flow of lake water to the engine (good) it would also restrict water to the header boxes (bad). The thermostat would also VERY likely drive coolant pressure WAY up the scale. Why can't life just be easy? Oops, forgot: This is a boat.

WHEN I WISH UPON A STAR:
I welcome any recommendations as to ELEGANTLY getting a coolant thermostat in the block while maintaining flow to the header boxes. In my dreams, someone would make a special version of the big, chromed coolant crossover/feed-tube (on the front of the block) with a built-in adjustable pressure regulator plumbed with a "pop-off" bypass line, which could be T-ed back into the header's coolant tubes (located just above the feed tube). And perhaps there is such an assembly and I'm just too new to know.

LEAN & MEAN:
I can tune the Dominator and address and/or fix most of the above maladies, but I still think that, considering the Merlin II's current useage, a stable block temp would go a long way toward making it a more civil water toy.

Thanks for any assistance and/or ideas on the matter, and I very much look forward to using this forum regularly to complain about something; even if I have to make it up as I go.

jrc in SC