Is there any way to gain more H.P. out of 310 mpi's without spending mucho cash (exhaust , cam , heads, computer upgrade)?

Nope......$$$$$$$$$$$$$$$$$$$$$

ditto...... nope.... tear it all down and rebuild from bottom up, the works... it's got weak internals and will fail if you put more hp to it.... been there... done it... rebuild from bottom up or drop in a new motor...

Good luck

I was told the same thing with my 310 7.4mpi.
I know of a fellow on here (SearayJim) who tried to up his 7.4mpi's hp. The computer was not programmed perfectly, so it dropped a valve and exploded a piston into literally a million pieces. The rod then went through the block. It was an ugly mess! I saw his motor. He ended up building a hot 540!
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Sooooo, I went out and found a complete 1999 HP500 carbed motor with 180 hours on it. I went through the top end, valve job, springs, etc., and checked out the bottom end, which looked perfect.

I ended up with about 10k in the HP500. I sold my old 7.4 mpi for 3k, so I have 7k in a wonderful Blue motor!!
Kent

Ditto....

Any Good Deals On Motors Out There New Preferably(2)? I Think Blues Are A Little Out Of My Range $$. What Do You Think About 496 Mag H.o.'s ??

I think that's exactly the direction I would go if I needed to repower.

I can't afford blue, and I want the Merc name on it.

Yup, you can always find HP hidden in your wallet!

The heads and injection design are the big restrictions in that setup.

Sell it whole and buy a used 502.

Now, I'm a bit apprehensive after finding this post. I've already bought a set of Edelbrock oval port marine heads, HP rods, and Speed Pro 9.19/1 pistons. I intend to use the stock cam and MPI intake, hoping the computer can deal with the mods.