boot

I know ,I know ! 10,000 times this has been answered ! But I need 10,000 & 1 .
Basic stock 1992 502 with B&M 250 blower and single 1050 dominator . What jets and power valves do you guys run ? This has 96's and PV's are 4.5's Seams a touch lean . We are going to go to 98's .WHat do you guys think ?

boot

bajamag

ck with ewb on the board he has same set up, he may be able to help you out. his motor rip's

John B

Alot depends on how big the power valve channel restrictions are. I used to run 92 jets all around and 4.5 power valves, but I can't recall the PVCR size but it was probably around .090". In the end I ran about 2 jet sizes bigger over #7 cylinder. If you have 5psi fuel pressure at wide open, and are lean you may want to install larger needles and seats, to make sure you maintain the proper fuel level in the bowls.

Mercury ran #98 jets without power valves in the 525 SC, but they ran rich all the time.

We ran the carburetor sideways to enhance the cylinder to cylinder exhaust temps in the mid range. These motors have 500 hrs on them, without problems, on a top gun.

Regards, JB

boot

THanks guys !
John ,Sounds like you did something right ! 500 hours ! THese carbs were done by Nickerson .Not sure what restriction they have . We are going to try some 98's this weekend .also installing V-6 modules that should have been there to start with .
Any more input would be great . THanks ,JOE

John B

Boot,
If you run 98's with power valves that open, you probably will be way too rich. remember an open power valve adds fuel the equivalant to a jet 8 to 10 sizes larger than what you installed!!
I had no luck with the v-6 modules. The advance was comming in at idle speeds 600-900, it made shifting and idle control difficult. I would only use these if you are backfiring at idle or when cold. Make sure your total timing is checked at 3500-4000 rpm, and don't exceed 30 degrees.
Good luck testing, and let us know how you make out.
JB

boot

THanks John . I'm going to try it this weekend . I'll let you know .

US1 Fountain

iTrader: (1)

Just checked mine.
124 all 4 corners. (not a typo)
5.5 pv on primary side

On a 502 w/250 & boost ref. 1050 dom.

Ran great last year! Not rich as one would expect. This carb was completely gone over by Bruce, so not sure what all was done. He added a lot of air bleeds and channel(?) restrictors, JER metering blocks and boost referenced it. Maybe this explains the large jets.

This was originally a Nickerson carb/blower package. I believe it had 98's all 4 corners, and 4.5 PV. , non-referenced. But I had nothing but trouble with it being to rich. 2 min of idle= loaded up. Boat was unusable.

Also run the V6 module. Never tried the V8 with the blower. May give that a shot this weekend for chits and grins.

John B, you saying the V8 module will give a better idle?
Thanks,

Jerry

joeyoffshore

CAll Dean or Brad at Nickerson Performance, they will have your answer.

KAAMA

iTrader: (1)

Call Bruce Wolff---98% of what he builds is for marine high-performance offshore boating---mild to wild and he's extremely well versed in tuning engines for blower apps or practically anything you have and does A LOT of carb work for marine engines. I know a lot of guys who have some BAD to the BONE boats from the Chicago area and Indiana who take their stuff to him. SGrady takes his 41' Apache to him just to tune the carbs and time the engines, etc. The guy is GOOD! Sometimes you might catch him in his shop on Saturday mornings---you might try 2 or 3 times between 9:30am and 11:45am. Otherwise you can usually catch him Mon-Fri 8-5. His number is: 616-422-1090 He is located in S.W. Michigan. I think he usually asks where you're from so he knows what elevation level you run the boat at.