Complete repowering of a brick
 

The title was from my last post about is it worth it to build my 27PC. Most but not all basically said no. So this thread is to document what the plan is and in the end guess I'll find out if it didn't work.

Boat 1994 27PC with a single 502 and B3 drive. Talked with Marine Kinetics (bob) and he recommends boring .030 over, aluminum heads, custom head and cam work and Bravo 1 XR drive. I would like to use a B3 for docking and slow moving my cruiser but have yet to buy one. Just picked up an HP transom from Costal Marine Export.

Previous engine always ran rich and top speed was around 45 to 47 (on a good day) with a GPS at 5200rpm.

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Intake
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Intake was oily
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There was a guy at our marina that had a 27pc with twin 454s and he said it did sixty. I dont remember what drives he had on it though. He has since traded it in on a new 31pc that also has twin big blocks, 496s i think. We have a 31pc also, the model before the current one and have 6.2s, i wish we would have got big blocks.

Didn't think there was enough room for twin BB in 27PC. I have to hang upside down to work on the starboard side most times. Ones there building today you can get twin 5.7HO. I'm not looking for top end as much as coming out of the whole and fixing my overly rich running engine. Have a couple other things also but that's boats

One thing that I see is you have the small corsa tips that are meant for 300 hp and under applications, even when diverting some of the volume through the y pipe. So, you have a VERY RESTRICTIVE exhaust there. Without running anything through the prop, your engine is being choked to under 300 hp. The boat probably ran a 454 (300hp) originally with a silent choice and no one has addressed the tips. Fixing your exhast restriction will more than likely fix your running rich condition. Bravo 3's are great for everything under 60-65 mph, especially if your boat responds well to stern lift....sounds to me like you really want a B-3. good luck!

Appreciate the input and will pass it by Bob prior to completing the build. Formula never installed thru hull on PC's that I know of. Boat originally came with a carb 7.4 and B3. I installed the thru hull and the silent choice when I put in the 502. Have EMI thunder headers that come out as 4 inch, then into the diverters, then thru 4 inch corsa muffler tips. Always figured 4 inch was plenty big enough for more then 300 HP.

Hey AllDodge.. Your project looks very interesting. I do not see any problem with your exhaust as far as HP is concerned. The oil in the intake looks bike blow by /blow back at idle to me. Prob have valves that are past their prime.. My guess is this is due to the transom exhaust/ flapper situation and maybe need for taller risers. First you MUST HAVE internal and external flappers in the transom exhaust. Lift up the external flapper and look inside. If no internal flappers are present or they are badly warped, then thats why your valves are toast and there is oil in the intake. MUST FIX this first. Personally with a single engine on that boat, I dont think you are going to get in the 60's without major horsepower. And if you do, it will be a ***** to plane off. But all boats are different and I will be watching closely. Bob Madera is definitely your best bet to build HP on that motor.. Good luck and keep us posted.

Chris

Seems like a lot of rpm on a b3 on a 27 ending with mid 40's please do tell how this plays out , think.your gonna find a little something somewhere that gives you some major speed increases ,remember to share

Makes no sense to me to spend 6-10k on a 15k boat to pick up maybe 4-5mph. Its your money though.

The engine has around 275 hours on it and it's been through a bad spot. When new (crate motor) it had a valve issue which I sent it back. Was told I was getting a new motor but after reinstall and about 20 hours it still was running like crud, almost as bad as the 454 I pulled out. Did a compression check and found some problems. Pulled just the heads and found out someone had installed 454 valves in the 502 head (to small). So new Icone valves and head work and has been running pretty good but rich. In hind sight when I found the valves I should have pulled to motor and gone through it. This is another reason to do everything this time. I'm seeing some blowby and the exhaust flappers were replaced when I installed the 502 and they still look in good shape.

Don't plan I trying to hit 60, 50 or 55 would be more then enough. Still may go with the B1 over the B3 but docking is a lot better with the B3. As for the risers, I mentioned it to Bob on the first call. The EMI risers are higher then the stock but not much. Had to send the diverters back to Corsa to have them lengthened because of the risers. May need to go get a high set for insurance. Will also need to have a bung installed for the Holley EFI. Bob did say I could use all mu internals if they check out

Griff has a point .if that motor has good compression and the boat doesn't have soaked foam or twisted hull you should have 55 already sitting there waiting to be found .we have a formula 496.b3 does 60 and a big pig 26 bayliner 305 mpi b3 runs 47 still think something is hiding in there somewhere ,