If complete means pan to carb and w/p to flywheel, then yes, if you switch to a 1.5 ratio upper or whole outdrive.
I'd also look at trim tabs to control porpoising...
a typical stock Mercruiser 5.7 engine makes 260HP, not 350
I very much created an account just to reply to you. I've seen your name pop up on 2 different threads shooting down people's ideas of engine swaps or re powering in some form. Im very much a gearhead by nature and am in the same boat as this guy. The 120/140 Mercs are lazy, underpowered boat anchors. 4 people in a boat doesn't even pull me fast enough to comfortably slalom in a 18ft boat. They only weigh 150ish less than a 302 ford and any aluminum heads would make up a good chunk of that. So why does the boat community have to be so lazy and straight edged? Why is 50mph just so scary to you with a 250hp v8? I've got a 21 footer with a 5.0 Merc that pushes 45-50 fully submerged prop and alpha one and it drives straight as an arrow. V hull. So what's the big deal about a v8 18ft V hull going 45 with a pre alpha? It most defenitly won't take flight at that speed and weight, 300ftlbs and 250hp most defenitly won't over power the boat. 45 most definitely isn't uncomfortable or unsafe for a similar shaped v hull. And a 4.3 merc is a common go to but has that similar 200hp output capable of pushing the same speed and only weighing a fraction less. Sure the v8 isn't the best all around option but they're cheap and easy to fix so why not? Let me hear the story of how you wrecked your v8 swapped boat, the saying is you can't knock it till you try it. So where's your 120/140 V8 swapped Merc and Pre alpha on a V hull? How much did it cost you? Did you buy all the parts or did you already have them? What boat? What outdrive? What kind of stringer support? What's the transom work look like? Where'd you source the yoke? How'd you route the y? What kind of through hull water inlet? Any cooling system mods? What was your top speed? What ratio drive? What prop? Stainless or cast? How many years did you have the boat? What kind of waters? Etc. Tell me how you are so sure it won't work without "deep pockets" like you claim. Give me proof you've first hand done this or seen this in your grasp and that it has failed for any reason other than poor execution.Re: 3.0l 120hp mercruiser to chevy 350 marine swap
He's a rev-head, and unless it can do 700 knots, he'll complain all day long... So let's help him get this madness out of his system.
Ok... First thing you are going to need to find out is if anyone else has done what you are planning to do... If they have, find out how the extra weight and speed affected the boat. Did it try to chine-walk at speed, that's the main concern. If you are not experienced at handling boats at high speed, then a chine-walk will kill you...
For that engine in that boat I would recommend you have a serious look at changing the ratio not to 1.5 but to 1.32, mount the gimbal housing 2" to 4" above 'standard' installation height, and have through-hull water pick ups. Then start looking at surface piecing propellers, because you're going to be going way over the blow-out speed of most fully submerged props. You'll also need to look into either dual cable steering or the old 'rope' steering system, and you'll need to have a very close look at the gimbal ring-to-steering arm. They are notorious for getting wear in them and you'll end up with very sloppy steering. Not a good look at more than 40 knots!
If you are going to change the gears in the drive, you are going to need the shimming tools. No, there is no other way of setting up the gear heights and backlash without them!
I hope you have deep pockets, 'cause this is all going to be very $pendy....
Chris.......
