HP500 jetting

[U.T.B.A.V-Drive man]

After looking @ the plugs I think the 850 carb might be over jetted. Anyone with a HP500 merc. know what the stock jets are?

[Havasu47]

It's an 800 CFM
Merc factory jetting is as follows...
Primaries:
Port - 81 Starboard - 75
Secondaries:
Port - 89 Starboard - 93

[U.T.B.A.V-Drive man]

It's an 800 CFM
Merc factory jetting is as follows...
Primaries:
Port - 81 Starboard - 75
Secondaries:
Port - 89 Starboard - 93
Thanks 47. So they crossed jetted them. How does the motor handel your boat, I assume it is a cat type hull. what is your RPM and with what drive and prop. I don't know why I though it was an 850 carb, I will look at the #'s

[Havasu47]

I dont have HP 500's, I knew the answer because I am a Merc. dealer.
They are good engines... not great ring sealing and you have to watch the breather hose as it will pull oil sometimes into the intake. This will cause the plugs to look rich sometimes.

[U.T.B.A.V-Drive man]

I dont have HP 500's, I knew the answer because I am a Merc. dealer.
They are good engines... not great ring sealing and you have to watch the breather hose as it will pull oil sometimes into the intake. This will cause the plugs to look rich sometimes.
I'm glad you brought up the breathers. on my v-drives I had a puke tank. Why do they put them to the carb? What does that do to the carb? Why not regular breathers on the valve covers?
thanks again
Jim

[Havasu47]

They are supposed to act like a pcv valve. We remove them and put breathers on the valve covers. They clean up the transom and run better.

[U.T.B.A.V-Drive man]

They are supposed to act like a pcv valve. We remove them and put breathers on the valve covers. They clean up the transom and run better.
Thats what I'm going to do. One other thing. To feed the 800 carb there is this small tubing coming from the water seperator to the fuel pump that looks to be 3/8 tubing W/ a 180 degree bend that even looks kinked, then a # 8 hose to the carb. Is that big enough to feed the carb @ WOT? (Hey I might as well keep going) I put on a crossover pipe W/ a bypass to the headers I was having problems with the thermostat opening and closing and the motor temp was goin crazy from 225 back to 150 then back again. I took the stat out and am in the process of putting in 2" fender washer W/ holes. I started out with a 3/4", the temp was about 110 so I put in one with a 5/8" the temp went to 130. Where should I stop. I always thought the chevy motors run best @ 180. I never had a stat in the v-drives, but I ran the water through the headers before the motor to pre-heat. What do you do on your motors? Thanks