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I have a 1997 Cobalt 253 with the 7.4 liter and the Volvo duo prop. I am just inquiring if or what anyone has done to get more power out of the engine. Is it worth it , how much power can the out drive handle. I don't need crazy power and don't want to spend crazy money. I am probably best off leaving her alone. However if there is something you have done to get more power, please share it. Thank you.............Doug

It will cost min a grand for every 1 mph. So start there. Or buy a Baja or a Donzi. Cobalt isn't made for speed. The 226 was prob there fastest hull. My little 220 with the 8.1 has issues getting to and above 60.

Big Block Power wrote: Fri Jun 05, 2020 9:05 am It will cost min a grand for every 1 mph. So start there.

Whats that first initial mod that's the most bang for the buck, or if you could only chose one?

BBP can answer correctly, but I would guess props.

Put a 496 in it. Lol

Sorry
Honestly the 454 has been a work horse for a long time. Your Volvo drive will handle what you want to do it unless you are going to go crazy.
Get labbed props. Get your ecu flashed. Do a supercharger. Do a cam, intake, exhaust. Is it fuel injected?

What Rpm are you getting out of it now at wot and trimmed out?

Donedroolin wrote: Fri Jun 05, 2020 8:21 am I am probably best off leaving her alone.

Probably but there are marine camshafts and exhaust systems that can improve your cruise speed and maybe some top end. 6k is about 6mph as BBP stated.
But even after you upgrade you still have a deep Volvo DP outdrive that will kill your top end above 60.
So where’s the pics??

If it’s the 330hp 7.4 it’s all cast internals, so no supercharger. Tune and some prop work will net you 2-3mph for around $2-3k depending on if you have your ecu tuned or buy a spare. As said, 60 is the wall with duo props. It’s doable to hit low 70s but not with that engine.

Pics!

How much timing will a 7.4 take? I know what my chevelle will take, just wondering if thats too much for a boat?

dustinm wrote: Thu Jul 09, 2020 9:01 am How much timing will a 7.4 take? I know what my chevelle will take, just wondering if thats too much for a boat?

Yeah, it won’t take as much timing as the Chevelle. You can try base timing it at 9-10* Initial, but watch idle rpm so you don’t beat the clutch’s up shifting in and out of gear. I’d just leave it at 8* and be happy with what you have. Unfortunately the 7.4 isn’t a great engine to try and squeeze budget power from.

no wonder they are so anemic, thats 70s smog timing there.

I just did a full tune on my 253 w/ 7.4gi and had my F5 props cleaned up by the pros. Made a noticeable difference.
Found a great deal @ jegs for a new distributor, brass contact cap, rotor and high output coil. Stainless terminal plug wires and iridium NGK plugs. Fires right up and has a noticeable difference in power.

Thank you I will look into this.