Hi Guys,

I have a pair of 365 mags in my 91 32 Pachanga, which have 106 hours (original) on them, both have very good compression and leakdowns etc.
The Boat runs 60, and would like to get a little closer to 70 if not just over....

As per most people on this board Im after a little more power!!!

Having read through the archive's Im leaning towards 250's or 6-71 and 4-5lbs boost (Engines are box stock and don't really want to crack them open)

Basically what I am after is a complete (as possiable) list of whats needed

Eg:
Carbs (twin 650's?)
Ignition (V6 module? Part number and where are they available from?)
Pulley Ratio to suit this boost level (4-5lbs) no intercooler.
Exhaust if need be. I have pulled the big waterlock box's out (factory sea-ray)

And anything else you guys could recommend?

Also where would be the best place to buy these items from? Im based in Auckland, New Zealand so want to be able to buy all parts that I need in one go as shipping is a PITA!!!

Any help is appreciated.

Cheers

James

The 525sc runs a weiand 177 blower. Blower size would depend on how much power you want to make. I think a 177 would get you over your 70mph goal. I'm not sure what generation your blocks are, for '91 I think gen v. Desktop dyno (which has been VERY accurate for me) puts my 365's (gen VI) @ 600+ hp at 5000 rpm's with stock roller cams.
For you ignition you can use the v6 module or fix the timing @ 32-36*. You need to install bigger oil coolers, inconnel exhaust valves and stainless intake, such as manley extreme duty valves. The stock 525sc uses a holley 1050 dominator, but if you get a bigger blower, dual 650's sound about right. Exhaust isn't as critical with a blower as it is N.A.. Cross sectional area is the most important. Witha small blower stock is ok, headers of course better. If you go with a larger blower, you definately should get headers. You should also add fuel pressure, oil temp, and boost gauges.
Try www.summitracing.com or www.jegs.com

If you want reliability then you need to pull the heads. Send to a machine shop and have a SINGLE angle valve job done.This is to keep the valves from burning up. Then have them polish the combustion chambers.This is to help eliminate detonation. Then reinstall the heads using Fel-Pro marine head gskts and ARP head bolts. Get rid of your water pumps and replace with a water crossover. Also remove your thermostats.This will keep your engines temps down. You will also need carbs that flow at least 825 CFM. Do these things and you will have very reliable turnkey motors. Also do not run more than 5 lbs boost with that type of blower.

Thanks guys for the heads up much appreciated, I may look into the 177 blower as if it's worked for merc then it sould hopefully be fine for me!!

Cheers

James

I am also looking at adding Whipple's to my boat and was wondering exactly the same thing - what else do I need to do to make this a reliable turnkey package?

2002 Sonic 358 with twin HP500 EFI motors (200 hours). The motors are bone stock and I plan to have the valve springs done over the winter - what else do I need to do? I would like to pick up somewhere around 10-15 mph with this package.

Thanks in advance for any help.

Although it's not absolutely necessary, but on a Merc 365hp engine it might also be a good idea to add an aftermarket exhaust high performance exhaust system such as a Stainless Marine or GIL or something comparable to those. Something else that isn't totally necessary is have the heads pocket/bowl ported.
By doing the bowl/pocket porting, and adding the Hi-Perf exhaust manifolds will help the engines breath better on it's own without totally relying on the assistance of the blower and helps keep the blower from working so hard, and helps keep the boost down and from coming in too soon and thus helps keep heat saturation down-------especially if you're not running an inner cooler and even more so with a small blower like a 177.

I currently do not run supercharged engines, but over the years I have deeply researched the option of blowers and blower types. I am not an expert, but my response is from what I have learned in my research when speaking to guys who know, and build blower engines. You'll will get some good ball park ideas here, but I would find a good engine builder who knows marine supercharger applications and follow his advice.