DIY_EFI Digest V4 #216

Shannen Durphey shannen at grolen.com
Fri Apr 9 04:14:24 GMT 1999


Stuart Hastings wrote:
> 
> I'm interested in improving the performance of my boat.
> 
<snip>
> Most marinized car
> engines have water-jacketed exhaust manifolds, because anything as hot as
> an exhaust manifold is a fire hazard on a boat. I think this means that an
> EGO is pretty much out of the question on a boat engine, 

Mount your sensor in the exhaust crossover of the intake.

 I gather (from reading the DIY-EFI archives &etc) that
> balance-shaft V6 TBI systems are fairly common (read "cheap") in
> junkyards; they were used in El Caminos, Caprices, and Astros. I haven't
> actually seen one, so I don't know if the intake manifold is Aluminum or
> Iron. 
Aluminum.

>Said donor vehicles probably all have balance shafts underneath
> their intake manifolds, and roller camshafts for reduced friction.
Worked on an early "Marinized" 4.3, roughly 88 vintage.  Had
aftermarket roller cam installed by Mercruiser.


> I'll interject something about my own capabilities here. I'm a programmer
> by trade, and while it sounds fun to disassemble ROMs and tweak BL tables
> with a laptop while under way, I don't have time for such a big project.
> EFI for my boat is only feasible if I can get a stock system from a junked
> car that will tolerate the marine environment and "bolt-up" readily.
> Ideally, I'd like to buy a complete system from one donor car, including
> distributor, intake, TBI, computer, sensors, and fuel pump.  I can
> probably deal with some throttle bracket fabrication, new fuel lines, and
> I think I can add a fuel pump to my boat's gas tank. However, if an EFI
> project gets any bigger, I can't handle it at this stage of my life (I
> have four kids, oldest is 8; they are why I have the boat :-).

Marine Holley system an option?

> 
 I presume that a
> properly-installed TBI system won't leak gas or fumes into the bilge.
> Correct?
EFI systems need a vapor handling system.  If hot fuel circulates back
to the tank, you get vapor build up.
Putting the return line close to the tank may cure this problem, but
may allow vapors to form in the TB supply system.
> 
> 5. My Prestolite non-electronic "marine" distributor has fine metal
> screening glued over the bottom vent holes. Can I "marinize" an electronic
> TBI distributor by duplicating this screening? A distributorless system
> elegantly avoids this, but then I presume I need the flywheel pickup that
> may or may not fit my heavy, clutchless marine flywheel. And my marine
> bellhousing probably doesn't have any provision for a crank sensor either.
> 
GM TBI as used on the 4.3 uses the distributor for the reference
signal, not a crank sensor

> 6. Are there any blatant misconceptions in my thinking, outlined above?
> 
> 7. If an appropriate TBI system exists (cheap, powerful,
> marine-compatible), what donor cars should I look for?

Pickups, S-10, Astro vans are the best choices IMHO.
Again, is aftermarket an option?
> 
> 8. Would I be smarter to grit my teeth and buy a used 4bbl for $450?
Ummm.. Do you really enjoy making changes to a working system?
> 
> 9. Would I be smarter yet to forget the whole project, because the
> existing 2bbl works fine, and an additional 30HP (17%)  won't improve the
> boat's performance by very much ;-) ?

Depends on your willingness to invest time, and your level of patience
if things don't work out as planned.

> 
> My research so far has been a few Fuel Injection books, and the DIY-EFI
> archives, and the DIY-EFI stuff is much more useful. I'm very impressed
> with the depth of the technical discussions on this list; thus far, the
> price of my research has been inversely proportional to its value :-)  .
> 
Somewhere around here there's an address to send donations. ; )



> Thanks in advance,
You're welcome.
Shannen
> 
> stuart hastings
> stuart at hastings.org




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