Jet Size

[shrfdeputy]

I just had my carb rebuilt by a guy who definitely knows what he is doing. Our boat had been running extremely rich and was leaving heavy soot on the transom. While he was rebuilding the carb he found both power valves were blown and obviously leaking, and someone had definitely had the carb apart and had messed with some things. He put everything back the way it should be, and he left the jetting the same. Today we put the carb back on at the ramp and backed the boat in. He set idle and then we ran the boat. It has excellent throttle response and holeshot, and it runs right up to 4600 rpm (right where it should be). It is still super rich. We can see a sheen on the water at idle, and there was even more soot on the transom when we pulled it out. He leaned it out as much as he felt comfortable with, but now I’m thinking someone may have switched jets at some point. It has 76 mains and 62 secondaries. How would I go about finding out what jets should be in this carb?

[Big Block Power]

You might get lucky and call Volvo and they can tell you. Or you just switch them and watch your plugs.

[shrfdeputy]

You might get lucky and call Volvo and they can tell you. Or you just switch them and watch your plugs.

My buddy thought Holley might be able to tell me, but I’m guessing Volvo changed things to their liking after they got them.

[Big Block Power]

You might get lucky and call Volvo and they can tell you. Or you just switch them and watch your plugs.

My buddy thought Holley might be able to tell me, but I’m guessing Volvo changed things to their liking after they got them.

Yea I don't know if holley would tell Volvo what they would recommend but they may have. It should be in the parts list at Volvo. Search your engine and carb and then see if they have a parts break down of the carb.

[shrfdeputy]

You might get lucky and call Volvo and they can tell you. Or you just switch them and watch your plugs.

My buddy thought Holley might be able to tell me, but I’m guessing Volvo changed things to their liking after they got them.

Yea I don't know if holley would tell Volvo what they would recommend but they may have. It should be in the parts list at Volvo. Search your engine and carb and then see if they have a parts break down of the carb.

I will do my best. When I’ve put my engine number in a Volvo search before it has told me it was a diesel. Lol

[Big Block Power]

Just look up the 7.4 gl. Do you have the decal on the engine yet? With the model number?

[shrfdeputy]

I have this straight from the Cobalt computer. The numbers are worn off the tag on the engine

[Big Block Power]

Take a peek here.
https://www.marinepartseurope.com/en/vo ... 35461.aspx

[shrfdeputy]

Take a peek here.
https://www.marinepartseurope.com/en/vo ... 35461.aspx

I just showed this to the guy who rebuilt the carb and he said it is really close, but my carb is just slightly different. I called Cobalt and they do not know. They buy engine and outdrive packages and don't have any say in how they are set up really. Their advice was to call a local dealer, give them my serial number and see if they can track something down through VP.

[Lockey14s]

I just had my carb rebuilt by a guy who definitely knows what he is doing. Our boat had been running extremely rich and was leaving heavy soot on the transom. While he was rebuilding the carb he found both power valves were blown and obviously leaking, and someone had definitely had the carb apart and had messed with some things. He put everything back the way it should be, and he left the jetting the same. Today we put the carb back on at the ramp and backed the boat in. He set idle and then we ran the boat. It has excellent throttle response and holeshot, and it runs right up to 4600 rpm (right where it should be). It is still super rich. We can see a sheen on the water at idle, and there was even more soot on the transom when we pulled it out. He leaned it out as much as he felt comfortable with, but now I’m thinking someone may have switched jets at some point. It has 76 mains and 62 secondaries. How would I go about finding out what jets should be in this carb?

When he rebuilt it did he put in new needle and seat? or did he just clean it? over time these precision parts can wear down slightly and you wont even notice just looking at it. is it a holley 4150?

[shrfdeputy]

Yes he replaced those. It is a 4150 and we think we may have just figured out the issue on paper at least. We think the primaries and secondaries are swapped around.

[Lockey14s]

there are a lot of different configurations for the 4150, but if you can get the build number off it then that should tell you exactly what the jetting is. i would contact holley directly rather than go through VP. the part numbers should be stamped on the carb.

[shrfdeputy]

We used the middle number and checked Holley’s website. That’s where we found the jet sizes are supposed to be something like 56 primary and 76 secondary. I believe it has 72-73 primary and 62 secondary right now. That would be almost 20 numbers too high in the primaries. That has got to be a huge reason it is so fat. Now we just have to find time to switch them around and mess with it. Unfortunately the highs are MAYBE 60 here this time of year so it won’t be the same as when it gets hot next year.

[Big Block Power]

It didn't want to fall on its face like it was flooded trying to get on plane? And really when going wot I would think it would not perform as good either. Like a flooded car. That's alot of gas going through those. Even mixed up. Maybe I'm goofed up thinking about this. On I'm getting a headache thinking about this. You had them backwards so then the secondary would have been running lean compared to what it was running?

[shrfdeputy]

It didn't want to fall on its face like it was flooded trying to get on plane? And really when going wot I would think it would not perform as good either. Like a flooded car. That's alot of gas going through those. Even mixed up. Maybe I'm goofed up thinking about this. On I'm getting a headache thinking about this. You had them backwards so then the secondary would have been running lean compared to what it was running?

We THINK they are backwards. That’s what Holley says is wrong anyway. The kit also came with 5.0 power valve and Holley calls for a 2.5. I ordered those today so hopefully we’ll be able to switch everything around and do some experimenting soon. It doesn’t fall on its face at all. It actually jumps on plane in a quick hurry, but it is super rich at idle. It’s smoking, you can smell it, and it leaves a sheen on the water.