Im exploring my options for a repower on my Commander, the motors are tired and slightly under powered in my opinion. My current set up is the 327F sbc along with the Paragon P-34B. My question; can I repower with a Big Block chevy and still mate up to the Paragon ? or should I stay with the sbc, dart block and go 427?

im not overly concerned with fuel consumption as I own a boat,  of course id only  like to do this repower once so any advice or similar experiences would be greatly appreciated.

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Those P30 series are only rated to 260hp, so anything bigger than a 350 is a gamble. If going through the process of repowering now is the time to also upgrade to a better transmission. I would recomend something in current prouction rated for a big block such as a 1018 Borg Warner or 63a hurth. I’m going with Velvet drives behind my 454’s.

good point, thanks for the heads up!

hey Mike, with you switching out your motor and tranny to the new 454 and velvet drives are you gonna have to size a new prop shaft too?

length wise?


- can someone help out with some info on the Paragon P - 34 B ?  rated Hp ? etc thank you

Couple thoughts but not in line with others. I put a pair of 454 330hp engines in our 35 and took out 350q. The replacement s had P25s which are junk. In discussion with Kalamazoo Marine gear we felt it was best to leave the P34s. Next step up is the P44 that has an additional band. Given how we used the boat which was easy we had no issues. We weren't backing down on fish or running big waves on Lake Michigan. We left the 1 3/8" shafts and attached bigger props actually the props and motors came from a mid 80's CC360 that were factory original. The boat ran flawlessly and cruised at 21-22mph at 3100. 454 parts are plentiful and inexpensive.
Mike W
Nothing I can really do with the shafts lenthwise unless I build new stuffing boxes and thru hulls, which I would really prefer to avoid. I feel that the 1 1/4 shafts should be adiquate on my 31 using a 1.5:1 trans. The Trojan I tookth3 454’s out of had 1 1/4 inch shafts behind 1.91:1 trans. The 1018 is the same lenth as my Paragon HF7’s so all the extra length in the engines will be infront of the transmissions. It will make things alittle tight to the bulkhead but should be workable. At this point though I only have to go on what I’v3 seen as my engines are still on stands in my shop. I need to get to tearing into them to see if/what work they may need.

Scott O'Neil said:

hey Mike, with you switching out your motor and tranny to the new 454 and velvet drives are you gonna have to size a new prop shaft too?

length wise?

I appreciate the info and you guys responding!  I'm going to look into big blocks aswell. good to know the P 34 should bolt up to them.

The Chevy small and big blocks use the same bolt pattern on the bell housing, also the Paragon Trans has a standard pattern that either a borg warner or hurth can bolt to.

Scott O'Neil said:

I appreciate the info and you guys responding!  I'm going to look into big blocks aswell. good to know the P 34 should bolt up to them.

Whatever you do, Scott, I have 3 words for you...torque, torque, torque. My 427’s may not be the newest girls at the dance, but my 35 cruises beautifully on plane at 2900RPM and 17kts all day long!

(Well, she used to until I had a piston bust apart and kill my port engine, but that’s another story - ha)

Regardless, whether it’s just me or a boat loaded with 10 adults, a calm day or nasty crosswind, if the bottom stays clean she never strays from the above numbers but more than 1/2kt one way or the other. I don’t even notice when the boat is loaded with people. This is mainly due to the torque of the 427’s. If I ever had to repower, I would place a very high value on torque figures of whatever I put in.
Thanks mike, I’ve actually put a lot of research into the repower idea. Your spot on about the torque. Everything I’ve read, and talked with several engine builders say the same.
I’m going with the dart sbc 427, with aluminum heads and intake. new exhaust headers. Will replace the old cast iron exhaust with custom stainless steel tubing. I have a local guy for that. Bonus weigh loss I guess... will keep compression low and spin the motors tops 4500 rpm wot. Builder will keep the power for the bottom end like you said. We’re gonna dyno then but he assured me they should be close to 450 ish HP
500 + lb tq ....
Only live once.

i used aluminum head before on 350,,i changed for vortec head who burn the fuel better at lower temperature ,,aluminum head are fuel efficient around 180 to 195 degree,my head was RHS 180cc ,,I did not see any difference compared to the 906 vortec,,and i can set up the timing at 32 full advance and run all day at 160-165 degree..with 87 octane and 9.1 comp ratio..read about this ,you will find a lot of info on internet,,

Thanks Paco, I’ll check it out. I do have a really well know race engine / marine engine builder doing the work for me . He’s very knowledgeable and experienced..., but please if you have some experience in a repowering pls feel free to chime in to help out!!

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