454 mag with b&m blower, tech qiestions???
 

hi i am new to the forum... i am on my 3rd Baja, 88 226 sport, 85 250 force, now a mint 88 240 sport.... i bought this boat out of storage, mint!!! always in side, super conditon... the previous owner never winterized, block, heads, manifolds cracked... i bought a used 454 mag, with a b&m 177 blower.@200hrs.. the previous owner turned this motor in a twin 33 foot avanti.. i bought his complete motor( full dressed, complet down to everything) i have a bravo one, with a 4 blade 26, Nickerson 800 double pumper... he would turn this motor at 5200-5400 rpms easily... i am only getting 4200... 0- 3/4 throttle i got 4000 rpms, come out of the hole beautiful!! but from 3/4 to full i only pick up 200 rpms..??? the only difference is he had cmi headers, and im running stock 4" manifolds... is this my problem??? or is it maby a dirty carb/ not enough fuel problem?? my friends are telling me to get headers, i know they help, but is it all my problem???? and also, what kide of Hp could this be? with headers vs. stock manifolds???? thanks for the help in advance.....

You might have a different gear ratio then the other boat to get them rpms if that is it you will need a new smaller size prop to get the rpm where you need them. Exhaust could help find anywhere from 200 up to maybe 400ish rpms as an avarage with that engine set up. And are you triming the drive up some while under way to help get more speed and mph? And yes the carb could hold it back also.

Check the ignition timing.

The carb seems small. 525sc come from merc with 1050 dominators.

How much boost are you seeing at WOT?

First thing I would check is fuel pressure. Should have 6-7 lbs at idle to full throttle. More will cause the needle to come off the seat and leak fuel into the running engine, less can cause all kinds of damage.

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???

i appreciate all the info,,, i like hearing for people who have way more experience at this than i do....

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??

im gonna look up the numbers tonite... im not sure what what size it is now....??

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)?