Boat sold. Buying a biz. Hopefully something nice once some debt is payed down!

I'll probably be on a 18' sea ray with a tower and blue tribal decal, an old maroon 21' regal, or maybe dr. Bobs big 46 sea ray.

Thanks for the advice I will keep boost the same Pulley's seem to be an issue to change, and I will go with aluminum heads that should help with possible detination.
Any idea what size runners would be best, dart heads are usually what I use. also I usually put in the 2.3'' intake valves , Anyone know why merc put in smaller intake valves on th e525's?

[QUOTE=MILD THUNDER;4123250]I helped out OSO member Wayne272 on something similar. We talked over the phone a bunch regarding cam selection and parts to use, etc. He had a pair of stock 365HP 454 Mags. With a cam upgrade (stayed flat tappet due to budget reasons), the 177 Blower, GM rect port heads, few other odd's and ends, stock shortblocks, he made 590HP at 5400RPM, and over 600FT lbs from a very low rpm, with a peak boost psi around 4.5psi. I think he's VERY happy with how his boat performs compared to with the stock 365 mags.

Thanks, this looks like exactly what I want to do . I have a new roller cam sitting around will post the specs to see what you think if it is a good match or not.

The stock GM rect port heads, normally had 2.19 intake valves. They used a 2.25" intake valve on the HP engines like the 525, HP500, etc. 2.3 intake valve is pretty large if your using a 4.250 bore block.


Smallest rect port dart head in aluminum, would be the 310cc runner. Your 525sc intake will be for a rect port. You'll need to watch the port match, as the GM style rect port openings, are slightly different than the Dart's . They are actually a bit larger. Port matching them would be a good idea.

I have only built N/A engines, The merc specs for the 525 and 600sc engine used a 2.190 intake, I was just puzzled by why this was done.

Also the cam I have is a roller 587lift intake and 610exh. Intake open@ 33btdc closes75atdc .Exhaust opens@82btdc closes36atdc
Will this work or is it too much for this application.

Strippers are also known as huffers right? Seems fitting they are much alike. Lol

I know this is a bit of an older thread but... the 2.19 intake works better on the smaller 454 bore.

Interesting thread. I'm contemplating a lot of the same for my 242LS. A 540 NA would be great, but I'm weighing the costs all around.

I know this thread is older, but MildThunder, i am about to do the exact builds you were just describing here. I have 365 mag motors, stock except for Crane gold roller rockers & MSD distributers. Im about to get a set of 525sc blowers, and they come with a set of fresh 1050 Williams carbs, but i was wanting to at least throw a cam in them while i have them apart, and was also gonna stay flat tappet for cost purposes.... I have always had good luck with Comp so i was gonna either do a grind from their Xtreme Marine line, or one of their Blower cams. Both are right around 0.570ish lift, but the Blower cam is on a 114lsa versus the Xtreme Marine 112, would either of these be similar to the Crane that your buddy used? I'm running stock manifolds for the time being so I'm thinking 114lsa may be better? (Do NOT want any reversion issues). Didn't think i could get as highs 590hp but after reading your post I'm awfully impressed and kinda pumped to try it out!

Stock exhaust is going to hurt you. I am assuming you mean stock 365 cast iron exhaust.

,I currently run a flat tappet Comp cams CB 280AH-14 (.050 232 in/237ex, LS 114, lift .547 in/ex) in my .060 over 525SC with 8.5:1. It pulls much better than the HP500 carb motor I had as a spare wihile rebuilding the 525SC.
Agree, exhaust should be looked at, I have CMI E-tops.