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mason01
08-22-2007, 07:46 PM
I have a donzi z22 with 250 hp 5.7 2 bbl carbed engine, what type of hp gains would i get from putting a 4 bbl on it

Updated question POST 3

smokediver
08-22-2007, 07:59 PM
there is a really good article in boating magazine doing just that swap . the gain was 6 mph ! http://www.boatingmag.com/article.asp?print_page=y&section_id=8&article_id=501&page_number=2
this is the web page ... only way i can do it ... sorry ... but well worth the effort .. !!!!

mason01
06-23-2008, 02:04 PM
I replaced the 2bbl with a 4 bbl and now the boat goes about 5 mph slower and won't rev above about 4300 rpm. Any suggestions to get the boat to rev higher into it's power band or what could be wrong?

VetteLT193
06-23-2008, 02:06 PM
I replaced the 2bbl with a 4 bbl and now the boat goes about 5 mph slower and won't rev above about 4300 rpm. Any suggestions to get the boat to rev higher into it's power band or what could be wrong?

Air fuel ratio is off... 'read' the spark plugs

mrfixxall
06-23-2008, 02:17 PM
I replaced the 2bbl with a 4 bbl and now the boat goes about 5 mph slower and won't rev above about 4300 rpm. Any suggestions to get the boat to rev higher into it's power band or what could be wrong?


What carberator? Did you change the intake or put a adptor from 2v to 4v? timing may be retarded..

mason01
06-23-2008, 02:24 PM
it's a 600cfm edelbrock and we did change the intake too.

I'll have to go check the timing and a/f ratio next time I see the boat

BigGrizzly
06-23-2008, 05:53 PM
I use to see this every day. Its jetting unless you did the install wrong. Are the secondaries opening?

mrfixxall
06-23-2008, 06:43 PM
it's a 600cfm edelbrock and we did change the intake too.

I'll have to go check the timing and a/f ratio next time I see the boat


you need to pull the intake back off and install a lifter valley baffel..look at the old intake,their should be a steel cover riveted to the bottom of the oe intake..that shield keeps the hot oil from baking the fuel before it can be sucked into the cylinders..so now the fuel is probably boiling which isnt good for rpm..

http://store.summitracing.com/partdetail.asp?part=MIL%2D32610&autoview=sku

mason01
06-23-2008, 07:15 PM
Thanks alot for the suggestions, I'll make sure to check everything in the next few days and keep you guys updated

Conquistador_del_mar
06-23-2008, 08:12 PM
it's a 600cfm edelbrock and we did change the intake too.

I'll have to go check the timing and a/f ratio next time I see the boat

It sounds like you have more wrong than just the carburetor adjustments, but I wanted to mention that the Edelbrock 600 comes set up very lean for economy. Be sure to get an Edelbrock calibration kit. You can change the metering rods and springs in about 5 minutes. I have never had to change the main jets on one, but I have always had to change the metering rods and springs to make them run richer. Bill

mason01
06-24-2008, 05:39 PM
It sounds like you have more wrong than just the carburetor adjustments, but I wanted to mention that the Edelbrock 600 comes set up very lean for economy. Be sure to get an Edelbrock calibration kit. You can change the metering rods and springs in about 5 minutes. I have never had to change the main jets on one, but I have always had to change the metering rods and springs to make them run richer. Bill

bought:cool: