Does anyone know what size cranks that mercruiser used in the earlier 540s, 4.25 or 4.375

the stroke is 4.375 and the bore is 4.440.its a good combination.

yeah 4.375 and with that rod I could not find any shelf pistons so when you bore it. you need custom pistons. Couple extra bills and lead time. I went with Diamond Pistons.

Don't mean to hijack but would like your opinion on the best combination .

how about 4.5 by 4.5.572 cu in.

j&e makes them for me,5 bucks a piston more than shelf piston,and i have them in 10 days.

i know where the last one that was built is and its still brand new on the pallett waiting for someonr to buy it..he wants like 14 k for it..serpitine set up carb to oil pan less theexhaust..

Thats what happened to me with the 557s which started life as 500bulldogs i like that combo. The ones i have now has 4.25 cranks with bowtie tall deck blocks.

4.750-4.750 + 673

I guess what i should have ask is how many ci's can be had from a Merc Blue 502 and still be reliable making 700+ n/a .