marinized 4.3L (was DIY_EFI Digest V4 #216)

[M. Jones]

Stuart Hastings wrote:
>
> I'm interested in improving the performance of my boat.  (snip)

Hi, Stuart--

I added an aftermarket (Holley 4D) system to my 351W-powered inboard, so I can 
share a few generic tidbits.  Shannen Durphey suggested mounting the O2 sensor 
in the intake crossover.  I did this, and it seems to work just fine.  If I 
were to do it again, though, I would devise a short, unjacketed section of 
exhaust (externally insulated) and mount the sensor there.  The Pleasure Craft 
Marine manifold design would make it relatively easy to fab an adapter;  don't 
know about your OMC's.  Less worry about whether or not you've done the right 
thing!  Or don't use the sensor at all.  I've run with mine disconnected and 
notice no discernable difference in performance.  (I can't say whether or not a 
stock GM system will allow this; somebody else on-list surely can.)

An external aftermarket TBI pump will likely work fine;  mine feeds 280 hp or 
so with no difficulty even down to the last few gallons in the tank.  I used 
the original pick-up which penetrates the top of the tank.  (My tank is 
vertically mounted at the transom.)  My return line is mounted at the level 
sender flange.  Through one complete season in some very hot whether, running 
for hours on end I've never noticed an increase in vapor coming from the tank 
vent.  Never had any hot-fuel problems of any type.  No start problems or 
lean-out or anything of that sort.  BTW the Coasties say that the pump is 
supposed to mounted on-engine or within 1 foot.

As to will it be worth it, If your boat is typical you probably won't see more 
than a 2-5 mph top speed increase.  Where you'll notice the difference is in 
pulling skiers up and acceleration in general.  The instant starts hot and cold 
make it all worthwhile, IMO, even without any performance increase.

I have an aluminum Edelbrock, with a zinc anode mounted in an unused water 
passage tap.  Even without the anode, in fresh water it will take 20 years 
before you run into corrosion problems -- especially if your boat is trailered.

HTH,
Mike Jones