bigboat28

I will look again for the five but I only saw the six on them. I looked on Holleys site and they did not list a 6. Yes mine look like the one the left.

blue thunder

You should call holley and get the box stock setup for jets and PVs of the 850cfm marine carb. Almost certainly the PVs are 6.5s, but probably only in the primaries. If yours have them in the secondaries, block them. Then what ever the box stock jetting is add 5 to each and you will be close. So if it is 72p, 84s box stock, start with 77p, 89s. After you get that we can work on the idle mix setting and getting it to run on the idle circuit. Also make sure the airbleeds are clean as a whisle. I presume you did this during rebuild, but it deserves mention because it can corrupt all other tuning.

bigboat28

What do you mean by "block them"?

blue thunder

Replace them with block off plugs.

http://www.summitracing.com/parts/HLY-26-36/

BenPerfected

If you have changed much in the Merc stock engines...like the cam then the Mercury stock PV size is likely not relevant. In most pleasure applications, if you elect to not use a PV then when at cruise you will likely be rich (black transom) and wasting $3+ gal gas.
The best way to set select a PV is by using a vacuum gauge. On the top end, we select the PV that will open at about 80% of the max RPM at WOT. As an example, if WOT is 5200 RPM, we would set the PV to open at approx 4200 RPM. This way you "go rich" only when you want a saftey net under high loads. This set up allows you to use much smaller primary and secondary jets...less fuel used for most of you boating hours.
At idle, you want to check that the PV you selected remains closed (PV size lower # than vacuum reading at idle). In most cases, this should not be a problem. If this is not the case, you will them need to some advanced tuning. Hope this helps.
Ben

bigboat28

Thanks

NEVERSATISFIED

Dale
The number on the power valve indicates the inches of vacuum the the power valve opens (ie: 6.5 would open at 6.5 inches of mercury). I will try to check my holley book you may have a 6 power valve which would be close to the 6.5 i'm not sure if they made a 6. Do not try to reuse your old power valves as they are probably dried out, in addition one sneeze or back fire and it usually pops the diaphragm in the power valve. This would also explain the terrible idle and black (rich) transom.

offthefront

iTrader: (1)

some info ..... BT is correct about secondary PV

http://www.bob2000.com/carb.htm

MILD THUNDER

iTrader: (3)

The main jet sizes should have nothing to do with a rich condition at IDLE. It sounds like you need to clean out your air bleeds, and make sure your carb is actually using its idle circuit. While its idling, if you can turn in the mixture screws all the way in, and it will still run, you either have a blown powervalve, or your idle speed screws are turned too high. once you crank the idle speed screws up too high, the carb will no longer function using its idle circuit. it will pretty much idle like crap, stall, high idle speeds, etc. Pretty much anything on the carb that you can adjust with a screwdriver, is for idle only. Powervalves and main jets are for high speed circuit.

Thunderstruck27

I like this thread! Getting some good info here.