Motor Ideas - what would you do?

[Footloose]

I have a 14,000 lb vessel with twin 502s, crane cam, rollers, holley 850 carbs and the heavy duty internals of all the late 90's 502s. I made a mistake when I repowered this vessel (project boat needed everything redone - a hull basically with arneson drives when I got it) with motors that are supposed to make 420 HP and high torque numbers. Builder was a flake so no dyno, no build documents, very little info and I have been fixing a number of things to get reliability.

Now I want to add HP and more importantly torque since the motors are laboring to get the vessel on plane. Whatever I do - I do not want to pull these motors out of the boat again so I am looking for reasonably cost effective top end things to add another 75-100 HP.

Another site of gofast guys rwho tend to be going for top speed numbers recommends baby blowers, improved cooling system, upgrade carbs and fuel pumps. I have done my homework and know I can do it for about $5k for both motors and would be seeing about 525hp and decent torque numbers.

What would you guys do?

[MOP]

I take you are still running the Arnesons, are you running vent tubes to air out the wheels to get it out of the hole. If you do not supply air to the props it is extremely hard to plane a bigger boat, you may very well want to research that aspect. HP will add top end but may not do much for getting it up on top!

Phil

[Footloose]

Still running the arneson ASD8s and upgrading to 4-blade clevers next weekend which should help. I tried some temporary snorkles (PVC) and it helped a bunch to get on plane....I immediately noticed that the valve covers were not puking oil anymore. I 'm having a freind make some metal ones for me next 10 days.

The internals I think are solid at this time and I am being told by my motor guys it is 8.5:1 or 9:1. I am picking up a compression tester this week - tired of relying on others.....I have about 50 hours on them pushing this beast around and cruise at 3500 rpm is about 28-30 mph depending on wind and load. However - you really get a sense the boat wants to run/cruise at a higher speed and that it wants the hull dryer. The blower solution is attractive because it is cheap, can be done in the water, and the dyno sheets of seen on low boost baby blower motors shows lots of torque from 2000 rpm up to nearly 4000. Perfect for what I am trying to accomplish. Down side is that I have no blower experience and fuel in the keys and bahamas can be questionable quality....could be the kiss of death. Anyway if it blows up in 20 hours - doesnt make sense.

It came with two blown and completely rusted/seized motors that were supposedly 500 HP Farera 454s with head work and oversized oil coolers....I should have gone 550 or 600 from day one. Live and learn.

Can cubes be changed in the water?

[Forrest]

43', 14,000 pounds with ASD8s? Sounds like she's askin' for a pair of diesels.

[Cuda]

43', 14,000 pounds with ASD8s? Sounds like she's askin' for a pair of diesels.
That's my thought also, but I'm sure the price would be prohibitive. Not just for the diesels, but to change everything fuel related on the boat. A guy told me it wasn't hard to power a performance boat with diesels from the get go, but it was pretty expensive to change a gas powered boat to diesels.

[MOP]

Blowers may or may not be the answer, you still may have to tear into the engine to run blowers. You say you heavy internals, what about pistions. They are one of the big keys in building a blower motor, I would be quizing the piston maker as to if they will survive!!!! Careful you may be throwing more wood on a fire that will burn the bottoms out of your pockets!

Phil

[Cuda]

Can cubes be changed in the water?
No, it either has to be bored or stroked to get more cubes, both of which necessitates the removal of the rods from the crank(bored), or the crank removed (stroked).

[Footloose]

Thanks guys - diesel was about a $100k changeover - I did the math and the boat is not worth it. Great info on the growing the cubes thing. I have had conversations with quite a few guys who have small blowers (177 or 174s) with 4 pounds of boost on stock 502s and they have gotten 4-500 hourds without issue. Some then went in and changed the exhaust valves to iconel (sp?) heavy duties, got some head work done, and some changed the cam out so that they could up the boost and go for more power.

Again - if I can get a reliable 525-550 hp out of these pigs - it would be ideal.