Go Back  Offshoreonly.com > Technical > Prop Talk
Need opinions on prop/gears >

Need opinions on prop/gears

Like Tree4Likes

Need opinions on prop/gears

Reply

Old 10-20-2019, 05:05 PM
  #21
Platinum Member
Platinum Member
Thread Starter
 
BBYSTWY's Avatar
 
Join Date: Jul 2017
Location: Sodus MI
My Boat: 1997 Nordic Heat
Posts: 1,053
Default

https://www.onallcylinders.com/2015/...m-performance/

one article that led me to thinking the valves are "bouncing" or "floating"
BBYSTWY is offline  
Reply With Quote
Old 10-20-2019, 09:57 PM
  #22
Charter Member # 55
Charter Member
 
Griff's Avatar
 
Join Date: Oct 2000
Location: Omaha
My Boat: .......32............. ............Active Thunder....
Posts: 17,101
Default

Originally Posted by BBYSTWY View Post
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
Didn't take it that way at all. Your springs are definitely way light when open. You should be in at least the 450 # range open.
And you may need the 5 blade with the -2 lower to get enough bite. Its all a process and making multiple changes can just make it more of a challenge to get dialed in.
Griff is offline  
Reply With Quote
Old 10-21-2019, 07:46 AM
  #23
Platinum Member
Platinum Member
Thread Starter
 
BBYSTWY's Avatar
 
Join Date: Jul 2017
Location: Sodus MI
My Boat: 1997 Nordic Heat
Posts: 1,053
Default

Agree 100%

The reason I went with the shorty is from researching what others have done as I'm not made of money lol...I found a thread about a shorty on a straight bottom heat from awhile back saying it gained some speed and handled better...and I can say without a doubt the attitude of the boat has changed for the better drastically. No more porpoise or hop while cruising and it feels a light "lighter" on the top end if that makes sense. It still takes massive amounts of trim as I've said but I think that is prop related and can be dialed out.

As for the springs...I am doing a cam swap and head rebuild(again) this winter and I know for sure they are not right and I want to straighten the motor out totally to take one variable out of the equation. The way I see it is the springs need to be done regardless and I've been told the cam profile is not great for a marine engine so doing that as well....If spring time comes and I still hit a wall at 5k then I know its prop related but I will know for certain that the motor is right and running to its full potential and I can go from there...kinda of process of elimination is how I'm approaching it...

Does that make sense?
Griff likes this.
BBYSTWY is offline  
Reply With Quote
Old 10-21-2019, 09:33 PM
  #24
Registered
 
Join Date: Jun 2011
Posts: 984
Default

Originally Posted by Griff View Post
BTW, more blades/blade surface area creates more stern lift, not more bow lift.
.
Not necessarily true. Blade shape, rake, pitch, trailing edge cup and shaft (barrel) length play a larger part.
Trash is offline  
Reply With Quote
Old 10-21-2019, 10:58 PM
  #25
Registered
 
Join Date: Apr 2014
Location: North Florida
My Boat: 90 Formula 242 SS
Posts: 461
Default

You may need more spring than you have, but it’s hard to imagine that you are floating at 5000 with 353# open. Hope you get things figured out. I know you have been at this thing for a while now and must be frustrated with a cam change at this point.
ph1971 is offline  
Reply With Quote
Old 10-22-2019, 07:46 AM
  #26
Platinum Member
Platinum Member
Thread Starter
 
BBYSTWY's Avatar
 
Join Date: Jul 2017
Location: Sodus MI
My Boat: 1997 Nordic Heat
Posts: 1,053
Default

Very much so....I just want the damn thing done so I can enjoy it and not hate it hahaha...this whole ordeal has caused me to resent the boat quite a bit lately but I'm hoping that a few good days on the water and maybe a couple races here and there will make it all worth it!!

The way I understand it is the open pressure is light but may be ok but the closed pressure being so light that when the intake event is coming to an end and the valves are almost back on their seats is when I may be seeing the valve bounce causing the RPM to stop rising....like I said this may or may not be totally causing my issue but it is in fact an issue and needs to be corrected...takes out one more variable and I'll know at the end of the day that the engine is right and can go from there.
BBYSTWY is offline  
Reply With Quote
Old 10-22-2019, 02:09 PM
  #27
Charter Member # 55
Charter Member
 
Griff's Avatar
 
Join Date: Oct 2000
Location: Omaha
My Boat: .......32............. ............Active Thunder....
Posts: 17,101
Default

153# on the seat should be fine. These are the springs used by many on the 500efi and 525EFI. which have similar cam size to you. https://www.summitracing.com/parts/i...5-sp/overview/
Griff is offline  
Reply With Quote
Old 10-22-2019, 02:14 PM
  #28
Platinum Member
Platinum Member
Thread Starter
 
BBYSTWY's Avatar
 
Join Date: Jul 2017
Location: Sodus MI
My Boat: 1997 Nordic Heat
Posts: 1,053
Default

But as you said earlier they are light on the open side...so regardless they are getting changed with a new cam and lifters as well...We'll see what happens when its all said and done...if I spend all this money for nothing oh well is what it is but now I'm questioning the springs and when done there will be no question so on less variable
BBYSTWY is offline  
Reply With Quote
Old 10-23-2019, 10:19 AM
  #29
Registered
iTrader: (1)
 
Join Date: Jun 2009
Location: Chicago
My Boat: 38 Flatdeck
Posts: 6,186
Default

500 and 525EFI are not blown engine so weak spring pressure may be fine.
I run 225/545 , no valvetrain issues , no float


The Crane Cams website ;
"Selecting the proper valve spring for any performance engine is important; but it is critical to proper operation of supercharged engines. Consider the fact that when the engine is in a "boosted" condition, the supercharger (or turbocharger) is trying to blow the intake valve open. The boost pressure actually reduces the intake valve spring seat pressure. This is extremely critical on engines with hydraulic lash adjustment. Proper seat pressure (working through the rocker arm and pushrod) is necessary to keep the hydraulic lifter plunger centered in the lifter body to prevent "pump-up." If an engine has 2.25" dia. intake valves, there is 4 sq. inches of backside valve area. Now add 12 (psi) of boost pressure, and you have reduced your effective seat pressure by 48 lbs. (12 lbs/sq.in. X 4 sq. in.). If you started out with 120 lbs. of seat pressure (static), you now have 72 lbs. of operational seat pressure. There is no way that 72 lbs. of pressure is going to control a 2.25" valve! For street use, the answer is to select a tall, mild-rate spring that assembles at a high seat pressure, yet keeps the open pressure reasonable over the nose of the cam to assure long cam life. (For example; a great spring on a Big Block Chevrolet with a hydraulic roller and a supercharger is our #96879 spring, which will provide 169 lbs. at 1.880" seat and 432 lbs. at 1.280" open with a .600" net lift cam.) Exhaust valve seat pressure does not need to be raised significantly on supercharged engines. Racing applications with solid lash adjustment do not experience lifter "pump-up,” but still need the high seat pressure to prevent the valve from bouncing on return to the seat against the boost pressure. Consult our easy to use valve spring pressure chart at the back of our Valve Spring and Retainer catalog.
Griff likes this.
ICDEDPPL is offline  
Reply With Quote
Old 10-23-2019, 01:55 PM
  #30
Registered
 
Join Date: Apr 2014
Location: North Florida
My Boat: 90 Formula 242 SS
Posts: 461
Default

700 lift and 6500 rpm?
ph1971 is offline  
Reply With Quote

OSO Sponsor
OSO Advertiser
OSO Advertiser
OSO Advertiser