Hi all,
I have a jet boat that I built. Originally I had built a 6.0 and ran it. Unfortunately it windowed the block first trip.

Being out of budget I picked up a 5.3 for free and freshened it up. Ran my heads and cam from the 6.0. Specs are

Stock 5.3 short block
Arp 2000 rod bolts
243 heads cut .030
Btr stage 4 ls1/ls2 cam 235/242 .621/.595 111lsa
Edelbrock Victor Jr intake
Holley 750 mech secondary 4150

It runs very well. Very responsive however being in a jet and with my impeller I can only spin to 5k at wot.

I think I'm missing out on a lot of power being that I can't get the engine to the rpm for the big cam to start making power.

My choices are change the cam up, or the impeller.

I'd rather look for a cam and not raise my cruise rpm.

So what are your suggestions for a cam that starts making power lower in the rpm range?

Honestly I'm thinking if I can get the 5.3 to start making power lower it might be able to swing the impeller higher too.

I just really think that I'm not giving this thing enough rpm to breathe and start pulling hard.

For what it's worth, the 6.0 swung 6400. And you could feel the cam come on around the 4500 mark.

Thanks

 

Is this a wet exhaust? I would lose the Victor, put on the dual plane. Then drop down to a 212-218 intake duration cam and cut it on a 110* LSA. Would probably run a 220/228 @ .050, 110* LA and 106* ICL and let the lift fall where it falls. With the cam/intake change it would really pickup in the midrange.

 

That's about what I was Thinking, probably stick with the Victor until budget allows.

It has dry long tube Headers, water is injected manually by me with a ball valve at the driver seat. For noise and cooling reasons.

I'm Thinking about the Btr stage 3 or stage 4 truck cams

 

I would go with an off the shelf cam for that combo probably be better do have a custom spec'd for the carb set up what's your timing like on your current setup are you using the 6ls box

 

Wouldn't go with off the shelf*****

 

thanks for the input. I called a cam grinder i have used a few times locally here in Glendora CA.

Took him a stock core (LQ4 cam) and hes putting a grind together for me. We talked for a bit and he said he does a lot of LS based stuff (i only used him for Gen 1 roller stuff in the past)

He was stuck between 2 profiles one being something around a 220 and the other close to a 224. I dont remember the specs. But he said he would chew on it for a bit then grind it. I planned on calling him today