Griff

But is that on a straight or stepped bottom??

Racerryan

Katanna

iTrader: (1)

You didnt mention how you are going to use the boat. Are you looking for all out speed, or cruise?
My straight bottom 29 Fountain with 1;36 drives is fastest and handles the best at top speed with 23 Mirage plus spinning 6200 at 81MPH.
That being said, I run it with 26 Bravo 1s which allows me to cruise 10mph faster at the same rpm sipping the fuel-3600 55 mph. 5-7 mph slower on the top end but how often do you run wide open.

phragle

iTrader: (3)

I dont know how much more you are going to try and run or if you make it to this side, but I have a 14" 24p sterndriver you could try

Griff

His is straight bottom and will probably need a prop that can carry the bow more.

BBYSTWY

So I may have jumped the gun a little by trying all the props I could get my hands on with the same results....something just wasn't adding up with it hitting a wall at 5k....so I dug deeper into my engine build sheets and talked to a few guys from here and turns out my valve springs are my limiting factor and after running the boat a little more and paying close attention I'm 99.9% sure I'm floating the valves....that being said like griff said I need something to carry the bow....I had a buddy take some videos of me running and this thing trimmed to the moon still runs very "wet"....once I get the heads done(again) with the proper springs I think I can get a more accurate test session and start really experimenting from there. I'm thinking a 5 blade whether it be a hydromotive or herring or even a maximus is what is going to carry the front end and net me the best cruise/top end

As to the questions about how I use the boat...I mainly cruise at the top end of my cruise speed range and try to stay out of boost but in a 20 mile run to get supper with buddies in their boats we will all do wide open blasts 5-6 times in that 20 miles because we are all speed freaks lol

Thanks everyone for the help so far...stay tuned for updates when the heads are fixed....and FYI they will NOT be going back to the builder that set this thing up initially...I don't like bashing people or shops on the internet but if anyone is curious to who screwed me so bad on this engine and is in the grand rapids Michigan area looking to get a motor built I can tell you who NOT to go to lol

Griff

I highly doubt you are floating valves at 5000 rpms. What size cam and what spring pressures??

I think you should put your stock length 1.5 lower back on and test. A deeper prop gives more leverage to carry the bow.
When you change multiple things at once, it becomes harder to go back to your baseline for answers on what works.
BTW, more blades/blade surface area creates more stern lift, not more bow lift.

Example.....When I had my 28 Pantera, it had a smaller upper pulley on 525SC when I bought it, but still only showed just below 6# of boost. It had a notched transom and came from the factory with a 2" drive spacer. It still ran too flat and too wet for my liking and high propslip%. I installed a 3" spacer. The boost went to almost 8# because the prop had so much more bite. It was more responsive to trim and carried the bow better. Propslip% went down, I picked up about 4mph at cruise speed and 2-3 mph at WOT.

BBYSTWY

I see what you're saying with the prop depth....I was just saying what brett at bblades told me...he told me a 5 blade will bite and carry the bow better with less trim and that's what he has used on heats in the past however they were stepped heats so he said it may be different...Maybe he misspoke I don't know

as for cam and springs...2 builders and 2 separate people from here told me they were surprised I got 5k out of the motor with whats in there...

cam...
adv dur..278/288
dur at .050 228/238
lift...612/.618
114 lobe separation

springs are 153 on the seat and 353 open pressure which on a blower motor especially is extremely light and its pushing the intakes open I believe

it makes sense because you can also see boost drop slightly when it gets to the 4900-5100 range and the motor hangs right around 5k...it wants to go more but I notice a big drop in torque and power when it gets there...its like you punch it and then pull the stick back to 5k...that's what it feels like and you can hear the motor almost surge up top like its hunting for RPM which from what I have read and been told is probably valve float

Not disagreeing with you at all so don't take it that way please just going off of what I have experienced, read, and been told

ph1971

iTrader: (1)

BBYSTWY

There is currently no hatch on it as I'm still in the testing phase...just a blower and bugcatcher sticking up in the air hahaha

Even with what should be 7-8 lbs of boost pushing on them out of an 8-71? You can watch boost climb to 5-6 lbs then when it hits the wall boost drops to 5 and flutters between 4-6