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Hey guys,

I'm almost certain this is being posted in the wrong place but I'm still trying to navigate this forum.

I have a 351w that I recently upgraded the top end on. The 351w is actually in a ski boat of all things. It's a MasterCraft from the early 90's. Originally everything on it and I mean everything was cast iron. I recently upgraded the top end to aluminum everything, 190cc heads, better roller rockers and a high rise plenum. It's topped off with a Holley 4160 marinen4 Barrell 600cfm carb.

This is where I need some guidance. I know the stock jets on the carb are #65. I was wondering with the 190cc heads how large I should re-jet this thing to. It runs ok at idle, kinda rough but not terrible, but when you try to accelerate above 2200 rpms under load the motor just slowly dies out. Leading me to think it needs re-jetting. Any advice on how to re-jet this thing would be appreciated. I have no good knowledge on carbs
 

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did it run okay before the head upgrades? is this the same carb, or a new one?
2200 rpm is awfully slow for you to be running out of fuel. that's just cruise rpm.

before messing with the carb, i'd be checking for proper fuel pressure at the carb inlet. you may have a weak fuel pump, a plugged filter, etc.
 

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yep i skied bihind a ski teak with 351 for years. replacing the cast iron not such a good idea. aluminun corrodes pretty fast in a boat. almost garonty your not getting fuel to carb. lean(too small jets) will make it pop under load
 

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did it run okay before the head upgrades? is this the same carb, or a new one?
2200 rpm is awfully slow for you to be running out of fuel. that's just cruise rpm.

before messing with the carb, i'd be checking for proper fuel pressure at the carb inlet. you may have a weak fuel pump, a plugged filter, etc.
Everything ran ok before I changed the heads. The carb is the same carb, stock to that motor setup. That motor tops out at I think 4200 rpm because it's a marine engine. I'm fine around 2200-2500 rpm with the throttle set, the issue is trying to throttle up from there. If I push the throttle open past a certain point the engine just gives up. Not all at once but slowly dies, like it's losing power or fading out.
 

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yep i skied bihind a ski teak with 351 for years. replacing the cast iron not such a good idea. aluminun corrodes pretty fast in a boat. almost garonty your not getting fuel to carb. lean(too small jets) will make it pop under load
The Stock jets are #65, I'm wondering how big I need them to be without being overkill, like a waste of fuel.
 

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figuring out jetting in a boat is a pain. nothing like fishing around in the bilge looking for that screw you dropped. make sure you take along a magnet on a stick
 

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Do you have a clear fuel filter on it? If not you could use it to troubleshoot a loss of fuel. When it dies, open the engine hatch and check the filter for fuel.

Did you check the check valve at the fuel tank? I had a 20 ft Shamrock with PCM 302 in it. The outlet fitting on the carb had a small spring and check valve on it. It that gets stuck it might not flow the right amount of fuel. If the tank has gunk in it, it might pick up something and make it starve for fuel. Lastly, if there is a screen over the pick up tube, it might get clogged. If you decide to remove the fitting on the tank, be careful...they can snap off. Getting the stuck piece out can take a long time. I know from experience.

Is it running hotter than in the past? might be boiling fuel like in another thread. I think most marine engines have steel fuel lines over the engine. How long has it been since the impeller was replaced. If it runs hotter than before, it might need a new one. Been a long time since I worked on a gas powered boat engine.
 

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Almost certainly not a jet issue, I would look at fuel supply...fuel pump, pinched line, float level real low. etc.
 
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