Hey Gillie,
What sort of WOT are you getting with the 150? Don't know what Bob Reiland's WOT was with the original 150 MC in the Moesly 21 "Unohu", but once he learned about the importance of using a vacuum gage and observing a limit of 5-7" Hg for max continuous/cruise power for decent exhaust valve life, he was limited to cruise speeds of about 18 kts. However Bob's friends said he ALWAYS ran 18 knots back then, regardless of sea conditions, so he kinda liked it when seas got up to around 4-6', when few other boats could stay up with him! The last engine he had in it was a 290 hp/350 Chevy/Volvo outdrive, and he said it was a 50 mph rig, although it was also thirstier than the 260 MC! Too bad he passed away a few months ago, as I'm sure he could give you some good advice on how much power you need to get the speed you want! You might also send a PM to Carla, as I'm sure Carl would know that answer!
There's no substitute for cubic inches, so I'd do some research on that 292 block and the Clifford Research site! Is there any way to install the OHC Pontiac head on the 292? With an aluminum head, you'd have to add FWC, so not sure if it would be worth the extra complexity. It's easy to soup up an engine with a hot cam and bigger carb, but doing that usually trades mid-range torque for high end HP and a rough idle, so not always what you want for marine use. A V-8 would certainly meet your WOT speed goals, but a well built 292 (ported head with a good 3 angle valve job and possibly oversize valves, Stellite valve seats, positive valve rotators, and file-fit rings for min gap/leakdown) might develop a surprising amount of HP while still making for a simple installation and easy maintenance. Only question would be how the cost of that would compare to a stock V-8 + boat mods. I suspect the V-8 might actually be a cheaper and simpler route if you could do the boat mods yourself.
Besides cylinder head airflow capacity, the camshaft is the key item for making power. If they make roller cams for that motor, that allows you to open the valves quicker with more lift for more "area under the curve" and more airflow/power without going too wild on duration that would screw up mid-range torque and idle quality. This would be a marine/RV type cam grind as opposed to a race grind that's often used on roller cams. It might also require solid lifters, so you'd also have to be willing to adjust valve lash occasionally, but that's not too hard once you learn to do it. Fuel injection really won't add any power relative to a properly set up carb. It might improve starting and idle operation, but it will require more sensors and be much harder to set up. I think a mildly "breathed on" I-6 and a more modern Alpha drive would be a unique and easily maintained set-up that could offer surprising performance if done right! Keep us posted on what you find out! Denny
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