We are definately going to need a bunch of more info about the bottom end... But...

Good luck getting 700 reliable, usable HP out of a N/A 540 on pump gas. I would set my sights on 600, and consider anything about that a bonus. This isn't a car or drag engine that you can spin to 7K. Torque is king in the marine world. Sure, 700 can be done, but at what cost? Solid roller? High compression and barely getting by on 93 octane? Horrible docking manners? No such thing as a free lunch, especially in a marine application.

What boat? Drive? What do you use it for? Whats your budget? I would throw 700HP N/A out the window. Not to say that it can't be done.

Trying to make more power in a marine application and "lil out of my budget" just simply don't fit. Sounds like you got the shortblock for a song. It's all up hill from there.

To get 700 hp out of a 540 you are going to need a real good set of cylinder heads i have AFR's on mine. Then your going to need about 10to1 compresson with a verry good camshaft a good single plane manifold and then most likely a 1050 dominator carb. Its not going to be cheap!

Aight thanks guys for the advice. From what u guys telling me and other readings i did I wouldnt be able to get the 700 and be reliable but I can come close . The boat im putting it in is 1984 willcraft excalibur. Previously owned a 22ft velocity with vmax 225 yamaha with phase three hydrotec kit on it that i got up to 77 miles out of. Im new to the inboard world but love projects. Soo down in the lab i go!!

Spend as much as you can on a good set of heads, cause that's where the power is. In rough numbers, from what I've done and seen, a budget build will get you 550-600, well ported heads or AFR's will get you to 650, and a stressed, change your valve springs every summer (or maybe every other) 6,000rpm setup can get you to 700hp - but usually only by someone who knows these engines well. Anything over 550hp and aluminum manifolds, like gils, will be holding you back, with 600 probably the limit, maybe even only 550, unless they are stainless marine's latest #III's, so above that means super expensive stainless headers that according to some are prone to failure, where-as a set of gils may last 20 some years as long as you take care of 'em and don't cook 'em.

In the end it all comes down to cubic dollars.... How much ya got....


I assume that's the 27'er? I would guess that 600hp with a bravo drive should get you to the 75 mph range? You'll also be at the limit for reliability, if not beyond it with a bravo, or a TRS in that boat if you play in rough water. I went thru 5 TRS's in 5 years with that same power in what may be a lighter boat.

X2

2 Much, PM me I'm in Kissimmee too, I'm just finishing up a nice small block build that Bob helped me set up.

+3

I know of someone on this site with upwards of 675hp with afr heads and a custom cam from bob (and supporting equipment). He is very knowledgable and willing to help.