How to get to 80 mph with a single screw
 

Hey All,
So I have a 95 27 Fountain Fever that I am trying to get another 4mph out of. Im running a stock 525SC setup and the boat tips out at 76MPH. Its seems to level off before the Chine Walkin starts so Im pretty sure I need to throttle through it a bit more to get to 80. I just did 400 Hour top end rebuild on the motor. While I did upgrade to Inconel exhaust vales and severe duty intakes I wanted to keep it all "stock". DMPE went through the blower for me. They said I was def ready for a rebuild and I also had them mill the rotors and put the teflon stripping in.

Soo. I am not really expecting that much more power from the valve job and while I should get a couple more pounds of boost from the teflon I still think I'm gonna be a couple MPH short of my goal of 80 MPH. As i mentioned I really want to keep the motor stock as possible (thats half the fun for me) so what do you guys recommend? Can I get it out of the prop? Im currently running a 4 blade prop and I'm pretty sure they already labbed that at the factory as part of the Blue Motor package. If so that was done in 95. Technology come a long way since then?

My other thought was to start messing with the blower pulley. If I do that is there anything else I need to change along with it such as fuel pressure? My understanding is that those little black Weiand blowers dont take alot of abuse...

I look to experience and appreciate the help in advance.

What rpm's are you turning at WOT?
4 blade..what degree? (most likely NOT labbed if stock from factory)
XR's? Stock lowers?
I'm sure you could turn the boost up but only some experts on here could tell you how reliable it will make your motor.

I'm sure if you can get one of the prop guy's on here to work with you 80 will not be that far off. Being's how props have changed alot in 15 years. Just my .02 Jeff

I am already impressed if you have pushed a 27 footer to 76 wwith 525 HP. I am thinking you might be able to get more reliable power with a cam change than increasing boost. You might be able to get some with a prop, but 4MPH by a prop alone is a lot especially at the speed you are already going.

Make it lose weight. My refrigerator equipped Checkmate (true) 28 footer will only do 71.5 mph. I think with one of reggies fast hulls (which is equivalant to a 25 footer I guess) you could up the boost a little and put the boat on a diet and be at your speed goal while maintaining reliability. Synthetic oils in every thing will help with reliability. Oh, and be easy on the stick.

The best thing you could do is bump the compression up to 9:1. If that is not in the cards, you can go as small as about a 3" top pulley and not be spinning the blower too fast. What top pulley do you run now?

Race gas.

Prop and check the bottom.

Fixx
 

Blackhawk outdrive:drink:

Bret at BBlades. Period. With a simple phone call to Bret(Make sure its Brett that you speak with, not his blocker), he can tell you on the phone if he can make your boat faster by working your prop. Well worth your effort. He told a friend of mine 3 to 4 MPH by lab finishing his props. Sure enough, 3.5 MPH gain over stock bravo 1's. And he didnt have to touch the engines at all! Cant say enough about BBlades/best bang for your buck!

You could go with a 120* stat, pulley change, and whatever needs to be done to the carb. You would be into less than $150. I dont see the stripping giving you much more than 1lb of boost.

PM Griff. He knows a lot about the 525SC.

93 octane. I run 9.5:1 with hypereutectic pistons and up to 6.2psi with no problem, although I do have alum heads. Thats why I said 9.0. I would not go over 6psi with the 9.0 though. Not sure what the stock 525scs had for psi. The problem is the blower is a might small for a 454 and the higher compression helps a great deal and allows one to keep the blower rpm down so as not to make too much heat. Its a real good move with the 177 on a 454.

A smaller top pulley on the blower and a BBlades labbed prop should get you there. No need to change the Tstat. Teague used to stock the 8# pulley which is about 2.75". You can still run 92 octane fuel and don't have to change anything else except for maybe the SC belt. Thats about all you can do without going inside the engine or adding a chiller.

I have a couple 10 rib ~2.8" blower pulleys with the merc spline if you are shopping for some.

Is this on a GPS Speedo??? 6.9HP/MPH on a 95 straight bottom production boat sounds really good. or am I just off on my calculations.

My old v24 Challenger was 5.3 HP/MPH however as you probably know they were one of the fastest production boats back then. That was a great bottom (slippery) but only about a 22 1/2 ft boat. Regardless I just think he wants to see 80 on the speedo.

Valako's comes out around 8 HP/MPH I think? I think the 525SC is over rated slightly also. Based on those numbers it would put this boat with a 525 at around 66 MPH. Never know maybe Reggie slipped a couple out with super sonic space age materials.

I agree with griff, smaller pulley(2-3 more boost) prop tuning will get you there if the 76 is GPS now..

It took my 93 27' Fountain about 650 hp to get to 80. And, that was doing nothing with the prop of drive height. But, I agree that if you are running 76 gps with 525, that pretty good.

Im surprised this didn't come up earlier. Yes it was 76mph on the GPS. Its a great running little boat. Im a pretty big fan of the 525SC but will give most of the credit to the hull design.

Id be interested in trying one out. Whats the price?

Here is a 27' Fountain for ya :eek:
http://www.youtube.com/watch?v=e_8c5tyH9VE

lots of engine to go 98....

It's JimV's NA565, just a little under 800HP. Its the boat that he won all the LOTO shootouts with.

Had a pair of 525 SC's for 7 years and never did anything other than change oil and spark plugs. They spent their entire lives with Super Chillers and the boost upgrade pulley kits. These were bone stock 525's and made 600+ HP. Sold this rig some six years ago and from what I hear they're still running strong. Intercooling a supercharged engine is the best way to get more power, thru higher boost, without hurting the reliability. Check into the chillers and the pulley kit to get you to 7 - 7.5 lbs of boost, bolt it on and just smile! :D

That was the beauty of the 525. It had so little comp to start with that you really could boost it up pretty good.

My guess would have been to upgrade the exhaust to a tube header and then get the prop done by BBLADES.

Prolly pick up way more than 4mph.

Be careful of just adding the smaller pulley without lowering the timing down to 30 or 32. I also sent my carb. out to Nickerson for a rebuild as the engine was very lean before the rebuild after adding the pulley. Last idea may be to go to big tube headers from CMI or Lightning.

What was the stock overall timing for a 525 sc, and what was the stock boost setting with the factory GIL exhaust?

What is your drive height? Fountains were usually set up correctly but I would check that first.

35 degrees....and 3 -5 psi....after adding the pulley it was around 7-8 psi

Stock timing was right around 35 degrees if I remember right, boost from Merc was at 4.5 - 5 lbs. With the chillers and smaller puley I was at 7 -7.5 lbs of boost, what you need to remember here is that the higher boost intercooled is in fact easier on the engine than the stock boost without it. I had the CMI E-Tops, ran the stock timing, with the carbs just a little on the fat side on the top end and they ran like champs, never a single problem. I remember reading an article on supercharged engines in Hot Rod magazine years ago where they stated the most reliable factory SC package ever marketed was the Merc HP 525 SC.

I don't think lowering the timing is such a great idea. My boats previous owner did it and the exhaust valves were done at around 150 hours. A stock timing curve has a lot of timing but it comes in late, like stated above.

30 or 32!!!??? Im currently running it at the stock 13 degrees. Please do educate me on this one!

My Bad. Yall must be talkin about WOT timing.

Those are pretty good numbers in that boat. Unless you have a screwed up prop, I seriously doubt you will get 4 mph by cutting on the wheel. And yes, I have some pretty good experience with a dialed in single engine.

If you want you can blow a few grand on a prop and exhaust for that extra mph or so. Bottom line, you are running good numbers and it will take some more power to get 80.

Don't get me wrong, a labbed prop has its place but big singles like power.

I run WELL over 80 in a single screw and have been fooling with them for quite some time.

I switched from the stock Merc Gils to CMI's and gained ZERO on the top end. Actually, Merc switched to CMI's the last year or two that they made 525SC's.

I ran just shy of 8# of boost for almost 300hrs without a chiller . Timing was set at the stock 35*. I only increased the carb jetting when I put in a bigger cam(731).
Like all Merc stuff, the stock jetting is set up on the rich side with #98 jets on all around and 6.5 PV's on both sides.

13* at idle with a 22* module that made full advance at 4250rpms for a 35* total. Stock boost is 2:1 overdriven for 5.5#.

what I do not understand, if you talk to the blower guys at weiand (who made the blower setup on a 525) or read the install manual, they recomend a max timing of 26-28 deg...whats up with this....I have always found backing the timing down under boost works best...Rob

Blower engines like all the timing they can get and as long as its not having detonation issues, its fine. The 7.5:1 static comp ratio in the 525SC allows you run more timing and boost without having to worry about detonation.

This little cutie last summer went 95 on my boat after screwing me once:drink: