AZ Speed - 35 Fountain 502's
 

I have upgraded my stock 502 MPI's on my 2001 35' Fountain. Prior to the upgrade I was running about 75mph at 49 00 rpm. I am now turning 5300 rpm running 80 mph. I have K&N filters, CMI headers, ECU upgrade, intake ported, more aggressive cam, Dart Pro One aluminum head. I am not happy with the top end, although the mid range is incredible. I have not had this set-up dynoed. Should I have expected more speed than this.

I spoke with Jim at AZ, and he said the next upgrade would be to a 540 working with what I have already done. This would take the hp to around 630 hp. Any ideas on the speed that I should be running? I still have my original Hydromotive 26 pitch props.

I have stayed away from supercharging because of resale and realibility. But I would like to be running close to 90? Any suggestions........... Thank you.

Get yourself some 8-71's...money well spent.

Maybe you should try labed props? From what i hear 2-4 mph gain

WaveSkimmer:

I have seen 79.3 on my 35 with 502 mags at 5000 rpm. I am running 23p mirage plus props. I have stainless marine exhaust and roller rockers - no other mods.

Unless you have a lot of other stuff in the boat, I would have expected more top end.

Waveskimmer:

You might see a few mph playin with props, but thats it. It takes horsepower to go fast, even in a Fountain. If you're really serious about hittin 90, try boltin on a pr of them 250 style blowers with a single carb. You already upgraded the exhaust, went with a little stiffer cam, right? Depending on the profile of the new cam (duration, lobe seperation) lift won't be that important, you should be in the ballpark for a little extra boost. You should'nt have any hatch clearance problems with the 250's as long as you dont get crazy with the height of the flame arrestor!!! A 3" one will work fine. Remember, a properly installed blower setup is very efficient and maintenence free.

Don't worry about the resale or the next guy, you want to enjoy your boat now,today, and if you wanna see 90ish, you're gonna need more a$$.

The nice thing about the blowers is that you can regulate the amount of boost used and where it starts to come in (rpm) just by changing a pulley, it's simple. Don't think for a second that your engine wont last as long with a blower as with naturally asp. Don't be afraid to try it, just keep your boost at 5-6 lbs at WOT.

Can you post the specs on the cam that you installed?
Frank

I appreciate all of the replies. Sounds as though I should be going faster with the given set-up. What is the brand of the 250's? Could I keep my mpi status with a blower? Would this be a better set-up than bored to a 540? This would cost another $20,000.

My current cam configuration is Crane, hydraulic roller 16535-16 long travel. Part number 168731. Lift: intake @ cam 345 @ valve 587, exhaust @ cam 359 @ valve 610. Rocker arm ratio 1.70.

Cam timing opens - intake opens 33 BTDC, closes 75 ABDC with an advertised duration 288. exhaust opens 82 BBDC, closes 36 ATDC with an advertised duration of 298.

Hope this information helps. The marina that put everything back together was not happy with the top end and thought the cam should have more aggressive?

Any thoughts...........

Weiand and B&M both make the 250 style blowers. You can usually find a pr of them 4sale here on OSO by goin on to "Parts for sale". Keep scrollin back page by page, I know I've seen them for sale here in the past couple weeks.

I'm assuming you have bravo drives. Higher torque produced by larger cubic inches is what destroys the bravos. RPM's and bigger HP will never hurt them, but BIG torque will killem. Keep your 502's

I don't think you will be able to use the mpi, as you will probably go to a single carb, usually a 4500 style 1050 cfm dominator.

The camshaft they selected was a very conservative one. The lift is OK, but it really needs quite a bit more duration. The 139741 (next one larger) would have been a better choice. It has 8 degrees more duration on int & exh which will give you more hp on the top. But if you decide to change cams, go for the 139651, it has 18 deg. more duration on int, and 22 deg. more on exh, plus it's cut on a 114 lobe separation which will work better with a supercharger application. The bigger cam will need to be advanced about 4 deg. so that you will have a good cruise speed around 3000 rpm, otherwise it will tend to run a little fat under 3000.

One other thing to check with the engine builder........ valve spring pressure on the seat!!!!! No matter what anyone will say........... you HAVE TO HAVE a minimum of at least 150#'s of pressure on the seat PERIOD!!!!! to run a sustained 5500 rpm for any length of time. DON'T let anyone tell you different. Been there, done it, seen the results...... valve float, and eventually if not caught in time, you'll drop a valve and destroy a engine.
If they used the springs recommended for that cam, you should be in good shape. But if you don't have 150# on the seat now, you're just askin for problems down the road if you plan on runnin the engs over 5000 rpm.

If you're really serous about the 90 mph, and the blowers, either pm me with your # or call me and I'll walk you through it. 708-579-5434...........Frank

Thanks for the reply. I'll give you a call to discuss. I am very interested in picking up more speed. Just wondering how many of modifications I have already made I will be able to use in the future? I guess that is why I was looking at continuuing with the 540. With this setup I would have around 630 hp. Would I have a lot more with a blower application? What if anything would have to done to my Bravo's?

I see that you are from IL, I run at Lake of the Ozarks.

Thank you.