I completely agree with Audacity! Get the safety factor, then the mods......the only way to go!!

Ditto
 

I waited too long.

If I had to go 80mph in your boat I would probably find a good used 502 Mag EFI and rebuild it and add a Whipplecharger. At the same time I would add an offshore water pickup and sea strainer and also hydraulic steering and a good drive shower. My guess is that you will need about a Bravo 1 30" also.

That will give you 80mph, probably more. The real question is: Do you want to go 80mph is a 21 foot boat? I would supect it will get very exciting after you pass 70mph and may approach terrifying at 80mph. There won't be much hull in the water.

:D As I said before: PUCKER FACTOR!! :D

Talk about pucker! I saw a boat like mine offered on ebay. It had a 604ci bad ass engine with lots of other mods on the boat. GPS at 110 mph! You couldn`t pay me to ride in that thing!

There was an article some years back about a 502EFI hammer. The boat was used for some prop testing and I believe they had it going 77mph with a Bravo labbed prop. Your boat weighs about 3400lbs with a 21* deadrise. I have to think that a 550hp motor should have plenty of juice for 80mph. You will need to run a Hydromotive Quad4 for that Hammer to handle correctly. There is major bow lift on the Hammer along with heavy chine walk. The Hydro. will solve the handling problems along with external steering like the others have said.

Here is a proven combo that a friend of mine has for his Hammer.
7.4 carb-300hp
performer rpm intake
stock carb tweeked
stainless marine manifolds
24p hydro. turbo prop (3 blade)
72.3 @ 4650 on radar in cooler weather and 71+ always.

Hope this helps a bit. Good luck!

as i recall tehhammer is a 21 degree hull. It will be fast but running at 80+ god forbid you hit any snotty water. You'll be flying for damn sure. you coudl biuld up your 310 a little bit maybe exhaust and a more agressive cam and run alegit 70mph. Save the big $$$ for bigger boat and hotter engine if you really want to go that fast.

I`ve already installed Stainless Marine Hi-Torque III manifolds, 5" outlet through 5" dia. tips (Yes...LOUD!!!) and planning to swap to RPM intake, 750 Edelbrock carb and a bigger cam. Hoping to see low 70`s. I will see how it handles and decide if I want to go any faster.

I have a 1999 Donzi 22zx. It has a whipplecharged 7.4mpi(310hp) which I estimate makes around 500 hp. It pushes it to 79-81 gps with a 30p Bravo 1 prop, Drive is a 1.50. This engine is reliable as long as you keep the mods to a minimum. Put a blower on it and leave the rest stock and you should be fine. That is if you get it tuned properly. Many members of this board have supercharged this engine with surprisingly positive long term results. For some reason this engine has gotten a bad reputation that I feel is unwarranted. I have about 50 hours on this setup and it has performed flawlessly. Compression is right where it should be and I have no blowby or oil consumption. Maybe I am lucky but I know several people who must have the same luck I do since they have no problems either. Supercharging this engine is in my opinion the best bang for the buck. The money it would take to swap some other engine could go towards a bigger boat, plus an engine swap most likely wont give you an extra 15-20 mph unless you spend lots of money.

The only issue is this engines L-29 heads. They have a fast burn chamber that is prone to detonation. Either swap to an earlier 7.4 head or have the L-29 chamber smoothed out. I swapped to a gen V peanut port head and have no issues.

donman,
i have sold baja's for many year's and would suggest for many reason's if your gonna sink that much money into the boat sell it and get one already done and a little larger. you would literlaly be throwing your money away on the baja.

Treadwell