motor builders advice
 

As you may or may not know of all the problems I have had with the new gm 454 HO
motors this year. I am now having the new motors rebuilt by a professional machine shop. I am looking for some professional advice on building these new motors. The boat is a 42' wellcraft excalibur eagle (go fast with a full cabin). the boat weighs approx. 11000 lbs. dry, so I figure about 15000 lbs. with gear, water, fuel and passangers. I am looking to build the motors with the most hp to get the most speed but with more emphasis on reliabilty. I am willing to sacrafice speed for more reliabilty, but I want it to go. with the 2 454 420hp I was getting approx. 55 mph gps. I am thinking about installing prochargers on the motors, is this a good idea or not or is there something better. I am looking for what type of pistons, valves, ect. to install. I would apreciate your help so i don't have to spend another whole summer dry docked

Re: motor builders advice
 

Not sure what your budget is but heres something to chew on. The bigger and heavier the boat, the more important torque is. You may end up spending lots of time and money on those 454's and never get the improvement you could see with a pair of 540's. Since you are clearly concerned with reliability, the bigger cubic inches would be less strained than the smaller ones developing the same hp. On to your question.

You need lots of torque, bottom end torque. Prochargers or any centrifugal blower really dont shine until they are spinning some. If you go the blower route, it would seem to me that a more positive displacement blower would be better for your application. Pistons? Forged. Valves? Dont skimp here, go inconel on the exhaust and severe duty on the intakes.

Re: motor builders advice
 

As many others will tell you here, it all depends on how much money you're willing to spend.
You could install mild camshafts and superchargers. With these changes you could reasonably expect 600 to 650 horsepower with a very nice idle.
If you still have the TRS drives you need to keep the horsepower at around 600.

Re: motor builders advice
 

Formula is right about centrifugal blowers. They belong on high RMP race application. BUT! You must take a look at the whipple chargers. You get off idle full boost. A very nice flat torque curve. Check out there web site. Cut and paste this link http://www.whipplesuperchargers.com/....asp?PageID=68
Hope this helps

Re: motor builders advice
 

From what I have been told the Whipple superchargers come on with off idle boost----which is much earlier than other superchargers designs. The Whipple will give those little 454cid engines the kick in the pants throttle response your boat needs.

Make sure it's a REPUTABLE machine shop that is acutely familiar with accurate machine work and knows what the hey they are doing when it comes to clearances and tollerances for a marine engine.

Also, althought it's not totally necessary, I would also add a set of aftermarket Stainless Marine exhaust manifolds. The aftermarket exhausts will help all the mods work together nicely by helping the engines breath much better thus giving even more performance once you add the Whipples. Just remember, torque is what moves the MASS---not horsepower! And torque is what you are going to need with a big HEAVY boat as you have.

Re: motor builders advice
 

If your are running Bravo 1's , the next thing to figure into the budget is a pair of good drives. Those B'1s will not last with Whipples and 15000lbs

Re: motor builders advice
 

Make sure your cooling system is up to snuff. Those engines will be under a huge load all the time. I remember when those boats were new. The guys that owned them were running 4000 rpms with the 420's all the time to get a decent cruise. The engines were lasting about 3 years between rebuilds.

Use the Eddie Marine 3 x 18 oil coolers with a thermostat. I run a plug in the oil filter bypass to make sure all the oil is cooled and filtered. Use a crossover in place of the circulating pump,(i know this will stir up some controversy but I've used them for years with no problems). Put in a 140 thermostat with 3-1/8 or 3/16 holes drilled in it. Make sure to use a crossover with a bypass hose to the thermostat housing. If you find you have too much block pressure, install a pressure relief valve. I've never had a milkshake oil problem. Good luck with the new engines.

Re: motor builders advice
 

A knock sensor would keep things together, it indicates harmful engine knock that is caused by lean fuel mixtures, bad fuel, too much spark advance or too much manifold pressure. 5 to 7 pound is all you need with a 8.5:1 pistons.
Don't get sucked into big boost. Only run the boost that your fuel and your timing can handle. This will all be determined by you engine designer. The more you retard the timing the hotter you get and then shorter the life of the motor. This is one of the biggest problems with the blower guys.

Re: motor builders advice
 

led...i have never heard of a knock sensor. where would i be able to get one?

Re: motor builders advice
 

Check out this link. http://www.eddiemarine.com/cart/deta...CategoryID=109