350 mercruiser stock switching to 454
 

Im looking to put a 454 Chevy in my boat and it now has a 350 mercruiser with alpha 1 what all do I need to change and anyone know what the 350 and out drive is worth it has 390 hours and a stainless 3 blade prop o and it sits in a 89wellcraft nova xl 23ft thanks

Are you putting a bravo 1 on?

If need to be but building boat motor and outdrive **** is new to me

I swapped a 420 H.P. 454 into a Donzi 22' classic that was originally powered with a 300 H. P. tempest. Everybody said it had to have a bravo, but i wanted to see how the Alpha did. I did not horse it coming on plane and always (almost) kept the drive in the water. The stock alpha lasted a season or two,then took out the upper gear set. I had it re-built with a set of better gears and it was still going several years later when i sold it. I certainly ran it hard ( the boat would run nearly 80 mph), but did not abuse it, so it can be done. I believe that the Alpha is more hydro-dynamically efficient than the bravo. Good luck

Ah, but a 22' Donzi doesn't weight anywhere near what a 23' Wellcraft Nova does. That makes a big difference.

First of all, welcome to our sport. (Or our way of wasting cubic bucks.) One thing you will learn pretty quickly is that most of the time, there's a very good reason particular engine and drive combinations are sold as original equipment. That would be because they work well together and are reliable. Many times when you replace one of those components with something more powerful, something else will not hold up to the strain. (Like the time we swapped in a 351 Windsor in where a 250 straight six used to reside in a '68 Mustang in college. Rear end went poof pretty quick.)

The 350 HP / 260 HP Mercruiser V-8 with the Alpha One stern drive is one of the most popular and bullet proof combinations out there. Unfortunately, the Alpha drive doesn't like much more than about 400 HP in front of it. Another thing that kills an Alpha is a heavy boat because it adds all sorts of strain to the drive. (Makes sense right?)

Mercury actually tried a 454 / 330 in front of the Alpha for one year in 1987 and the shrapnel count went astronomical, so they dropped it. When you get above that, the next step in the line is the Bravo One.

So if you really want to go faster, you may actually find it easier to buy a faster (stock) boat. First, it will be built to take it. Second, you won't butcher the resale value of your current boat.

Hope that helps.

there are always used gimbal,s and bravo drives in the swap&shop,and priced fairly.pretty easy swap ,i have one in the shop that belongs to a customer,i think he will sell it cheap.

Boat is goin to be paid for in spring plus I want to build it my way and do some custom work to the interior that will set it apart from just buying a faster stock boat nothing I own is kept stock I also hate payments so dont want to buy another boat even know it would be easier but thank for all the info

I totally agree with "too stroked". My point was that big blocks and Alpha's can work in some cases, providing you "handle with care". Certainly not the best combination for a heavy boat.

I do not think going to a BB Chevy is completely worth it. The 383 stroker that Mercury is using to replace big blocks does extremely well. I replaced a gen V 7.4L 4bbl with the 357 4bbl and it turned the same prop with 100 less RPM @ WOT. If we had gone to the 383 we could have gained 75 more HP. But at 350 HP you are still best using a Bravo drive.