Quest for 80's
 

Have a 29ft fountain fever stepped hull. Motor is hp500 with 177 blower. I really want to get into the 80's next summer after the rebuild. I am trying to stay with the 177 blower and maybe adding a superchiller to get some extra hp. I'm just curious on what kind of hp I will need to get into 80's. I know the simple way is to go to a bigger blower, but I'd rather not. Boat all ready has a 28p bravo prop and I'll probab have it labbed to get an extra 1-2mph.

What are you running now?

Also I know you say you don't want to go bigger but it's highly advised. There is a lot of good info on these blowers in the q&a section. The 177 just creates too much heat and was really meant for a smallblock street app. Depending on what you run now you may almost reach your goal with just a bigger blower. The cooler charge and better air flow will up your power a good bit.

Bigger blower doesn't mean harder on the engine. In your situation it would prolly be easier on the engine.

http://www.offshoreonly.com/forums/g...er-sizing.html

It easily ran 75mph, 77 was the best at the beginning of the season but the motor just kept dropping power everytime out. I know a bigger blower will help, just can't quite swing the extra cash right now.

That's not good, how are you compression numbers? Might be time to do some refreshing, if not, I think playing with the prop would be a good way to go.

What year is your 29?

The motor is out and torn apart now. Just want to know what hp I need to get 80 so I can tell the engine builder what to shoot for. Right now I'm going for around 650-675. It's a 97 fountain fever.

I don't think you are going to make that kind of power with a 177 unless you spin the hell out of it. You might want to look for a 250.

Rebuild the motor good enough to make 700HP with a 250 blower...sell the blower you have and buy a used intake/carb to run this season or until you save enough money up to buy the larger blower...IMO.

I have a 95 27 fever with a 525sc, all stock except running 2 extra lbs of boost 560ish hp. I have seen 80.9mph just me and about 15 gallons of fuel, 77.8mph with 2 people and 60 gallons of fuel, and I have seen as low as 75mph loaded down in poor conditions. I would say I would need 625hp to run 80's on a more consistent basis, but there would still be those days where I would be 78-80 loaded down in poor conditions. I am pretty sure the 29's are the same speed as the 27's with same power. In mine if I wanted to hit 80's all the time no matter what 675hp is what I would be after, as loaded down and in poor conditions I think I would still be around 80-81mph. However, light load day and good conditions could probably see 85-86mph. From a 502 base 500hp you will need to upgrade to a 250 blower as the 177 is too small for you now, so definitely will be too small for some bumps in power. At minimum open up the stock heads to get them flowing some air. a good ground blower cam, and go to a 250 blower. That should get you 675ish hp on about 5-6lbs of boost. The 177 is maxed out at about 625hp, and on a stock 088 head set up the heads will be the limiting factor in a blower application at 625-650.

I have looked into this, as I want to be able to hit 80's with a moderate load frequently. I talked to Bob Madara about a cam and roller set up that he says will get me 600-625hp on a stock 525sc so that's probably what I will be doing this winter as I want to keep the motor relatively stock for resale. If I was shooting for anything more then 675hp I would do a nice aluminum AFR type head and a 420 blower underdriven.

Do you have a -2 imco lower drive unit on this yet?
If not that could get you there

Have you checked the x dimension? How far is the prop shaft below the hull? A -2 imco drive on straight v's i have seen a big difference on mine and friends boats. Fountain has always had there x dimension much higher than most boat builders.but it is worth a look

The motor is at competition marine in Moscow mills mo. They are gonna give me a few options and know what my goal is. They have a 10-71 blower there for sale with dual carbs that's pretty reasonable. Just kinda curious what I could get out of my 177 and hp500 carb?

You don't get the gains from shorties on fountain stepped hulls like straight hulls like the outlaw or scarabs. It really depends on the XD but when I looked into and was really close to pulling the trigger it just wasn't worth it. With a -2 on my hull you are in 5 blade territory, and they don't plane out well at all. Its hard to say whether a -1 or -2 shorty would get a worth while gain, vs the cost and negative effects for planning

How much boost are you seeing now with the 177? I wouldn't do a 10-71 personally as I think its too big for what you are after. A 6-71 or 4-20 would be ideal honestly, even an 8-71

Honestly I have no idea what boost it was pulling before. The owner I bought it from said 3lbs. Now that it's at a marine shop they are finding some real strange things do I'm kinda questing the people who had it before me on how well it was setup. I completely agree with you guys on needing a bigger blower I just honestly don't think I could swing the extra cash right now on top of rebuilding the motor. I brought up the 10-71 since the shop has it for sale for another customer for 2800 with two dominator carbs so it's not a bad deal. If I could find a 250 blower with a carb all ready on it for cheap I would go that route. Just 7k to rebuild the motor and another 3k for a different blower the cash just isn't there.

Yea I hear you, I have a handful of things I want to do this off season, and just not sure if I will get the money together for all of it.

For starters, the 800 Holley is way too small for a HP500, with a 177 blower. As, is, the 177 on a 502.

What I would do, is sell the 177, and grab a 250 blower. Then, rebuild your HP500, but install a 525EFI camshaft. Sometimes you can find them very reasonable here in swap shop with low hours

The 800 carb is too small for the 177, and the 250. Minimum, you really want a 1050 on there if you have to run a single carb. A 250 blower package with a 1050 dominator, can usually support around 700HP. Twin carbs, about 750ish. I highly recommend twin carbs on the 250. If you happened to find a 250 blower with single 1050 used, throw the 1050 on the 177, sell that package. Pick up another 800 carb off an HP500, and throw the 2 800's on the 250 blower.

I really wouldnt waste my time with the intercooler under the 177. Your blower is already gonna have a hard time making boost on that engine. Adding the chiller, you're gonna have to spin it even harder, to make the boost from the restriction of the core.

i went ahead and picked up a used 420 blower with twin dominator carbs. So should be looking for 750hp. Hoping that will get me well I to the 80's.

Mild Thunders advice is golden. Take one of those 1050's and sell the 177 as a package to recoop some money, then sell the other 1050 to get money towards picking up another 800. Or you may have to just sell the 1050 and 800 and pick up the size you need. I wouldn't think you would need twin 1050's for this set up, by Mild Thunder would be able to shed better light on this on for the 420 blower

Nice pick up OP, you'll be much happier and better off in the long run.

Definitely get rid of the dominators and the 177 and use the money to buy the correct carbs.

Yeah all i have to do is measure that everything will fit ok under the hatch. I know this will push my boat into the 80's. The shop that's building it said this platform can get me close to 800hp but I've told him I'd rather stay around 700hp. The Bravo is gonna be screaming for mercy with 700 much alone 800. Ot thing I am kinda curious is what kind of speeds will a 700hp fountain get mid 80's? Doesn't seem like there's many single engine fountains with big hp. Also how are the 29's handling at that speed?

Well motor is all back together and ready to go back in the boat. 735hp http://s369.photobucket.com/user/kma...tml?sort=3&o=0

The Rpms are low since we kept the stock rev limiter at 5400. If we changed some stuff around and let the motor go more rpms and builder was confident it be 750hp or more. Boost is only at 5lbs, we planned at going with more boost and aluminum heads to push it up over 800hp, but after everyone's advice on here about the poor bravo one I told me to keep it under 750hp. Those guys at competition marine real now hire stuff.

Posted at same time.

Did you change cams ?

Yup went with their custom blower cam, idles like a stock motor. The torque was in the 700's too.

The video is gone

:eating:

http://s369.photobucket.com/user/kma...tml?sort=3&o=0

Try this link

Well took the boat out for the first time today with new motor. Ran 77mph with a bravo 28p prop at 5400rpms (it was sitting on the rev limiter). Swapped out with a 29p hydro motive prop and couldn't get on plane. Kept blowing the prop out as soon as it would go to roll over. So kinda looking on advice on where to go to next? I heard hydro props run mor pitch then a bravo prop. So I was thinking about maybe trying a 30p bravo prop. We did have 6ppl on board, full cooler, and full of fuel though. So am I headed in the right direction with a 30p bravo? Or should I look at a 27 or 28 hydro?

Sounds to me like you picked up some power with the larger blower. I'd try a 30p bravo and run it again. The 5400rpm limited sucks !

Ya that's why I am gonna try, trying to figure out why the 29p hydro kept blowing out. I couldn't get on plane at all, just blew out right before it roll over.

Prob just not enough cup in the blades.

With the prop slip calculator my slip for the 28p is around 17-18 percent. I mean it hardly sounds like the motors working to get to the rev limiter. The motor dynoed 735hp, will a 30p help this or will I have the same problem getting on plane? Really don't want to jump up to a 5 blade.

boat should be dead in the 80's...even before, need to get rev limiter up...need to turn 5600-5800, make sure running LH prop, either 28 or 30 hydromotive should be the trick, make sure that you are getting boost, if not take off flame arrester and run without to see if that changes...something not right with your setup...

Not sure if I missed it somewhere but where did the motor make peak power at? With 735hp in a stepped hull 29 fever set up correctly you should be hitting the 90's or damn near close to it. Its kinda weird that the hydro is blowing out, fountains pre 2000's love hydro's, some people do experience a negatives here and there getting up on plane, but nothing crazy that I have heard. With 735hp and a 5 blade probably is not the best idea, specially with a LH rotation drive (if you are LH rotation you should look into getting a billet top cap), and really if you have a stock x dimension a 5 blade shouldn't be necessary. I have a 95 27 stepped hull fever and I am right around 4.5" below the bottom on prop center line. At 77mph you are way off the mark of what that boat should run with that power.

Hydro props are true to pitch, where bravo props are a little under pitch. A 28p bravo 1 is around 27.3-27.5 where a 29 hydro is a true 29.

Original motors power was unknown. New engines he ran 77 banging the limiter. Not 77 mph max.

I've seen it many times when a prop simply has the cupping washed away, or a poor repair removed much of it. I've seen high x SSM boats not plane with 18" 5 blades, but lay right over with 17" 4 blades. Its not always x dimension or blade count.

Another thing to keep in mind. Sea level, salt water can be a lot faster than a freshwater boat in a bit of altitude.

Is there a dyno sheet to see where this engine would be happy at rpm wise ?

I got 17.26% using 27.3 for the pitch on the 28p bravo 1. Without knowing where you made peak power, and with it being rev limited at 5400 its really hard to say where you need to go prop wise. Since you are having problems with the hydro, try a 30p bravo and see if that keeps you off the limiter, then you can make a determination of what you are really at. Was either prop new? Or do you know the history of both props? 1 or both may have been worked on or refinished at some point and is the reason your slip is up there. I am on average around 11% slip in my 27 with a 26p hydro set up by hydro for my boat, and all it is is the diameter is cut down to 15" and the blades were sharpened, not thinned, just sharpened. I bought the prop new from hydro with the work done. I picked up 2-2.5mph and about 100rpms from it on the big end. If you get your slip down in the 13-15% range and can spin a 30p bravo in the 5600 range the boat should be in the 90-92mph range. I would take it out with 2 people, and half of a tank of fuel, and test a 30p bravo 1 and see if it puts you on the 5400 rev limiter still. If it does you should be 86-88mph area there, and then you need to raise the limiter, or prop up if 5400rpm is where it made peak power, which I am sure it was higher then 5400.