I have a 1984 30' scarab with twin 454's trs drives nose cones plan on building 454, 10 to 1 comp, rectangular port heads ,older torker the one where the carb is turned alittle,1" spacer ,750 cfm holley dp df ,msd ignition.lighting headers reduced water. My first question is what would be a good camshaft for this engine ?according to lighting 240 degrees at .050 max . Second question using a trs drive what failures are common with this drive . Third question what prop would work better a 23 p mirage ,25 p mirage or 23 p clever . Fourth question what mph can i expect?

Just my .02, but you may want to reconsider going with a 10:1 comp ratio engine. That is kind of high for a non-racing pleasure boat application----especially if you have cast iron heads. I really think you will end up being sorry, but it's your choice. All, it takes is one careless moment or some bad gas at the pump that you weren't expecting and you'll have a melt down on your hands. I would allow myself some cusion in the compression ratio department and look for HP in other ways if I were you. A hydraulic cam in the 222*/230* on 112* lobes would be as about as large as I would go. The headers are a good thing and will definately help all the other mods you do. But, if it;s not too late just do some short side radius work and clean-up pocket port work on those heads and reduce your comp ratio down to 8.0 to 9:1 comp ratio. I would also consider using a dual plane intake manifold especially if you are using a rectangle port head on a 454 which is too large. Something like an Edelbrock Air-Gap intake would serve you well I think. There may be some other guys who might chime in here to help you out as well with your ideas. "rmbuilder" is at least one good one I would listen to.

Did almost the same in a 30' 78 Scarab. Cam was something like 224/234 hyd and it ran great with 23" bravos at around 5200rpm. Bad chine walk for some reason so I never got it topped all the way out. I'm guessing 450HP each and 70-72??? VERY HEAVY boat. Was a little slow out of the hole with the single plane cam but I thought the torquer was the way to go for top end.