turbosonoma

i have an 89 lightning with two 454's in it, turns out they popped the frost plugs when the last owner had it, i pulled both engines, and was going to go through them cause they had 427 hours on them, was also gonna add the weiand 256 blowers, problem is, i dont know much about boats at all, this is my first project, what should i do as far as freshening up the engines? compression? cam? carb? stock heads decent? a guy in town has a set of new 525 heads that he removed from his boat to upgrade, are those a good head for me to upgrade to at a good deal? or should i just keep stock ones?
Thanks for ANY help.

Griff

The biggest question is how much HP do you want to make and how much do you want to spend????

You should be able to make a reliable 600HP engine with the stock rect port heads, 8:1 compression, and 5lbs of boost and run on pump gas.

What kind of drives do you have????? Going much beyond about 600HP with a TRS or Bravo drive is asking for problems, especially in a heavy boat.

Pwrbt33

Like Griff said, big heavy looooong boat! Its a drive killer with big power. You might want to change over to 502's if you can, less $ to make 550 to 600 hp. If not leave your 454's in, do some nice head work by a reputable shop and stick a 256 Weind on top or something smaller like a 174 and make 525 to 550 hp. Theres a lot of 525sc's still running today.

Good luck!

John S.

KAAMA

Exactly what model of Merc 454's do you have in your 89 Lightning? Are they the 330hp, 365hp, or 420hp or something else? Even though these engines are all 454's they have different parts in them and may have an effect on what you want or may want to do with them. What length is your Lightening? I agree with Griff, if you already have the GM rectangle port heads and you want to add blowers then those heads will make 600+ horsepower, BUT be warned that they do have a tendency to CRACK between the seats which is not a good thing.

Are the heads your friend is removing from his engines the old Merc 525hp heads from Merc's supercharged engine? Or is it from the Merc 525hp EFI naturally asperated engine?

turbosonoma

i would like it to be between 575-600, must be reliable, and run on pump gas, i dont wnat anything to ridiculous, hence to 575-600. the boat has trs drives which im hoping will last if im nice to them, they are new, as the previous owner had them rebuilt/replaced a few years ago after he hit a log, and they havent been in the water yet so im hoping they are decent.

turbosonoma

they are the 420's, boat is a 42. what heads would that motor have on it?

badluck

I did the 420 to SC conversion in my previous boat.
Used the B&M 174, Holley 850 boost refered, MSD AL6 and IMCO exhaust. Kept the boost low (4psi) due to the 8.7:1 comp for the 420's. The internals were stock, but new bearings, rings valves etc.
Troble free package if done correctly. I picked up 600rpm over the old 420's in 8000lbs 38' with TRS.

bl

KAAMA

Well, you off to a pretty good start with the 420's then! And YES, they come stock from Merc with the rectangle port GM heads, and the 420's come with a 4-bolt main block and all forged parts....cranks, dimpled 7/16" rods, pistons! They also come stock with the Crane Gold roller rocker arms and cast aluminum valve covers and Holley carbs if I am not mistaken. If I am remembering right the only thing that may be a compromise is the exhaust system that came stock on that engine model----it's a cast heavy cast iron system that would leak. You'd be better off with an aftermarket aluminum exhaust manifold system like Stainless Marine, GIL, Dana Marine or something along those quality lines.

With that many hours on the engines they should be refreshened and have a cam installed that is a little more user friendly towards an engine that is destined for a supercharger. If your wallet can afford it you might want to look into a hydraulic roller cam/lifters. RMbuilder/Bob Madara of Marine Kinetics can help you with the cam application. He has helped many guys here on OSO with cam selection for about $60-$70 additional for the cam. Bob's a great guy and full of integrity.

Make sure you choose an honest, reputable machine shop that is familiar with marine offshore performance engines---so pick a good one. Just remember, those GM rectangle port heads have a tendancy to crack between the seats....it's a roll of the dice if you decide to continue to use them.

If those heads that your buddy is removing are from the Merc 525hp EFI engines then they are made of aluminum and would be a better choice over the GM rectangle port heads---you wouldn't have to worry about them cracking. I believe they're about the same CC size, but perhaps someone else can chime in here.

turbosonoma

the boat already has gil exhaust/manifolds on it...
i have a good machine shop lined up already.
what is reccomended as a good complete rebuild kit? or is it not really neccesary to do all new internals after that many hours?

badluck

I don't think you will find a complete "kit".
I suggest new bearings, rings, valves (inconel exhaust), rings, and good head gaskets if the engine is in good shape. You can keep the 420 flat tappet cam (same as the 525SC), but you would be better off with a hyd roller.

bl