5.7 Up Grade !

[Sam]

I've made the decision to up grade my 5.7 / Alpha gen II combo. This will be a hands off project meaning I'll hire it out. I intend to increase the HP to 300-325. My ultimate goal is to get my sixteen into the 65mph area. Based on what others have reported with their boats I think this HP range should do the trick. Any opinions ?
What a dumb question.

Sam

[HP 600SC]

There is no such thing as a dumb question,
unless you dont ask it!
65 MPH is right on the money for that combo!
if you go with a 1:50 ratio you will use a
23 Mirage plus prop.
keep us posted on your progress!!

[Formula Jr]

You will easily get there with 300HP.

Now to handle it you'll need to look at three issues.

A. The built in Hook
B. Trim Tabs.

A. If you run a straight edge on the chine and rear hull near the transom you'll see your boat has a depression built into the hull. This is a normal hook built into 16's to help them plane off and are useful up to about 60 where they cause all manner of handling problems. What it mainly causes is a jumping motion combined with a slight walk. Though you can drive a boat like this with some practice, it will scare the hell out of any passenger. Filling in the hook with glass till its fair will stop the jumping motion but will not stop the walking motion.

B. In this application tabs are critical. Go with a 9 inch bennett system. These will one, replace the lost hook on planning off and two, extend the running surface of the boat to make it stable with no walk past 60. You set them so they are just touching the water at speed and then use the drive trim to find that sweet spot to run at.

Anywhere past 60 in a 16 is a wild ride.
Oh and the third thing; Make peace with your god. :)

[Sam]

The first thing I did when I got the boat was to put tabs on it. I wouldn't run a boat of this type with out them. As far as the hook goes that's a TBD for now.

Sam

[mattyboy]

Good luck on your quest Sam, Keep us posted.
JR are the hooks on all the 16s I was under the impression the newer ones didn't have them? On my 68 16 the hook is extremely noticable. at 55 my boat is a hand full trim tabs and all, I believe my prop has to much hull lift (rake or cup I can't get the 2 straight) for handling you want more hull line wet for speed more hull dry. the more I think about it , it gets more like golf in search of the perfect swing or setup, the perfect balance, some days you beat the game some days the game beats you. I think performace boating is more dangerous than golf, but if you ask the guys I play golf with they would say they would rather ride in my Donzi then be any where near me on a golf course :rolleyes:

Matt

[Formula Jr]

You can have a dry boat and be in control. I have seen so many people with "can be fast boats" that never freken understood proper trim. I was in a small non-donzi with a 454 and the guy would not let me show him how to trim it out. He got scared.... The guy kept saying "I like it flat. " My hidden thought was: Why the hell did he buy this boat? It was a very expensive well made boat.. a boat that just had the wrong owner.....

The rack ............. The rack..... Yes, Tatoo. The rack.

[Sam]

I met with the mechanic today in an effort to get the ball rolling un my upgrade project. Here is what we have decided.

1.Cam
2.Intake
3.4 brl carb
4.Heads
5.Valve train with roller rockers


Now the question is what brands ? Keeping in mind that I want parts that I can rely on and will deliver performance for the buck. I have a list of Mfg's that I am aware of but I would really like to hear what brands you have worked with.

Thanks
Sam

[Formula Jr]

I don't know nott'un bout them chevys.

[PaulO]

If you want to do something really different and potentially great, take the hook out of the hull and build a small pad in about 6" wide tapering from the transom to about 4' forward. This will increase top speed and get rid of the chine-walking problem. The downside is a theoretical ( I don't think you would notice it) decrease in rough water smoothness.
PaulO

[Murphy]

To upgrade that 5.7, start with Dennis Miller's book. You can buy it here: http://www.amazon.com/exec/obidos/ASIN/1557883173/qid=1007091666/sr=8-1/ref=sr_8_5_1/002-9097482-8045615

A lot of what you do depends on the year of the engine. Pre-87 is a different animal from 87 and beyond. Vortec is a whole nother beast. I'd add pistons and rods to your list, especially if you go with different heads. Also, is that block a 4-bolt main? If not, you may want to upgrade the whole engine. In the end, if you're going to sink the dough into it, a high performance SBC at least ought to have a good block. Also, decking the heads will ensure proper quench. If that isn't done right, all the add-ons in the world won't make up for it. If your guy can't do it in his shop, he'll have to send it out. Head gaskets can make you or break your critical clearances at this point too, so read up on it. Heads come in the small and large chamber variety. What ones you use will determine what pistons you use, and what compression ratio you want to achieve (10:1 max is recommended for marine engines). Also, there are the light-weight and the heavy-weight versions to consider. Intake... do you run in salt water? If so, go cast iron. Aluminum doesn't hold up well. Even in fresh water, there are some good reasons to go cast. It should be the high-rise, dual-plane variety. After testing carbs, I'm back to my Rochester Quadrajet. Most racers will still tell you the Quad is a great carb if you know how to set one up right. Talk to your builder about balancing. Also get him to gasket match intakes, etc. Dennis Moore's book will give you a lot of advice on the finer points. Don't move too fast and take time to learn your options. The wrong choices can end up costing you a bundle for no performance gain. Good luck and let us know how it's going.

Murph

[Sam]

Murph thanks for the pointers and the book rcommendation I just happened to have ordered it a couple of days ago. My thought is, if replace pistons, rods ect I would be better off buying a crate motor. There is a point when it stops being an up grade project and turns into a total rebuild. My motor was very fresh when I bought the boat last winter. There were still hone marks in the cylinders. I had the motor check out from head to toe last spring and it ran great all summer. I expect to pay $2,500 to $3,000 for the complete job. For this I will get the speed and reliabilty that I want.

Sam

[Ranman]

Sam, You're on the right track. Good luck with the upgrade. When are we getting together for drinks with some of the MI Donzi folks?.

[Sam]

Good question ! maybe we should start a post and see what happens. What do you think about doing it before christmas.

Sam

[Tony]

Sagbay has a post over in events/gatherings regarding Michigan guys...check it out.