I have a 1985 mercruiser 350 that I want to convert to Holley TBI injection
and I was wondering if they make an exhaust manifold that has a place to
mount an oxygen sensor or can the original be machined for one?

Two problems.....

If they are cast manifolds, they are water-jacketed. You could machine
them, however, you would also need to manufacture a special sensor adapter
to thread into the jacket and seal. (difficult)

Second, the Holly system is not marinized or certified for marine use, that
I am aware of.
Don't let the Coast Guard, Sheriff, or DNR see it..........

Best bet would be to update your engine with later model Merc direct
injection.
"Michael Letchworth" wrote in message
ink.net...
I have a 1985 mercruiser 350 that I want to convert to Holley TBI
injection
and I was wondering if they make an exhaust manifold that has a place to
mount an oxygen sensor or can the original be machined for one?

I installed the Holly Throttle Injection on my 350 Chevy Marine engine.It
worked ok ,but the problem i had (and in a boat its a BIG problem) is if i
turned on the key without starting the engine,the spray nozzles would spray
So hard the`d fill the carb. with fuel and run gas in the bilge in about 10
seconds.Holly blamed everything but their unit.After talking with some
engineers that helped design the unit they told me i`d have to install
another battery just for the injection unit and keep it over 11 1/2
volts..didnt feel safe with it so i fought with them and they finally took
it back.that was 5 years ago,maybe the`ve updated it since then.



"Michael Letchworth" wrote in message
ink.net...
I have a 1985 mercruiser 350 that I want to convert to Holley TBI
injection
and I was wondering if they make an exhaust manifold that has a place to
mount an oxygen sensor or can the original be machined for one?