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Originally Posted by kenny j
(Post 2913808)
it was showing 5-6 lbs of boots at 3/4 throttle... and you could hear the blower screaming under the deck....we diddnt take it up too full throttle too often cause thats where its acting funny.. but i was noticing that the boost was comming in at like 2900-3100, is that too early??
If its an 800 cfm carbed reworked by Nickerson, it probably flowing more like 900cfm and that is sufficient for what you have. |
Originally Posted by blue thunder
(Post 2913886)
I don't start to see boost until about 4000rpm. I'm not sure about this but I believe any restriction to airflow (exhaust) will cause higher boost reading than the specified ratio should make. I presume you have a 250cfm blower? What is the drive ratio (crank pulley dia/blower pulley dia)?
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Originally Posted by kenny j
(Post 2913798)
the guy i bought the motor from sold me the whole set up,(motor, carb, outdrive, prop) so the timming is still the same as when he ran it, the only things different is the fuel pump and exhause.. im running a malory 110 marine pump, and we set the fuel pump a few times, its around 7-8 at idle, and between 6-7 at wot.. i have a gague on the fule line so it takes two ppl to see it.... but im real sure that headers will help me in this situation, but i dont think its my complete problem???the previous owner turned this motor in a twin 33 foot avanti
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this is pretty much his settup
http://www.cpperformance.com/detail.aspx?ID=9413 and im almost certain it has a holley 1050. The drive ratio is 1.5.. bravo 1 that motor should be around 500-550 hp that would run that boat 70-75mph, a 26 B1 should be perfect around 5000rpm |
Blower motors are less sensative to exhaust manifolds than NA motors. They shouldn't hurt the motor 1000 rpms. Maybe a hundred or two. Somthing is really wrong to see that big of a drop.
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Originally Posted by sabo
(Post 2914523)
this is pretty much his settup
http://www.cpperformance.com/detail.aspx?ID=9413 and im almost certain it has a holley 1050. The drive ratio is 1.5.. bravo 1 that motor should be around 500-550 hp that would run that boat 70-75mph, a 26 B1 should be perfect around 5000rpm |
at 4200 rpm, the boat is runnind 64 on a gps... and thats at 3/4 throttle... the boat stock did 60mph with the 330hp it came with....
i was worried it may be over prop'd, but the boat planes out beautiful with the 26 4 blade(like 2500 rpms, it rolls right out of the no wake zone)... i had a 23 3 blade on it stock, and it was noticabley harded to plane out with the stock motor.... it seems like the motors running great on the bottom end, its just between 3/4 and full theres something missing....?? |
When you say it's acting funny at WOT, what do you mean exactly? I can tell you from experience that things can go VERY bad if something isn't right on a blown set up. There's less margin for error.
Do you know where the timing is at when you get up into the upper range? Have you checked to see that WOT on the stick is actually WOT at the carburetor? |
Originally Posted by TomZ
(Post 2915234)
When you say it's acting funny at WOT, what do you mean exactly? I can tell you from experience that things can go VERY bad if something isn't right on a blown set up. There's less margin for error.
Do you know where the timing is at when you get up into the upper range? Have you checked to see that WOT on the stick is actually WOT at the carburetor? yes, we checked and at wot on the stick, its wot on the carb butterflys... we double checked the fuel presseure tonite, and at 4200 rpms, it was pusshing 7 1/4... the motor performs great up to 3/4 throttle, but from 3/4 to full, it does almost nothing....??? everyone out here at my lake is telling me to get headers,,, but i have a deep down feeling that headers will help, but not my only problem... i dont know what the timmings set at, but i know i didnt change it from the previous owner, and he was getting 5400rpms out of this motor... its definatly not over propped, caues it planes out beautiful at half throttle, with no tabs....???? something definatly not right, and unfortunatly im not very mechanical, and im reliying on other ppl to help me.... |
What happens to the boost past 4200rpms??? Does it increase, or stay flat or decrease???? Its possible the blower belt might be slipping at higher rpms.
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