A friend wants to put a LS1 in a jetboat. The only thing we are wondering about is the O2 sensors. Since water runs through the exhaust manifolds, what's the solution? Is there a way to tune without O2s? Any ideas?

 

Well actually the water only goes into the exhaust at the risers. The manifolds before it are on water jacketed. Also, There are only a couple of solutions for manifolds currently (unless he is going with water injected headers).

Most boats don't use O2 sensors.

 

Search on speed density tunes.

 

Yes...you can tune it to run quite well without O2 sensors. Also, if you decide not to go the injected route a carb could be used...but yeah, if you want to stay injected then O2's aren't required. Running no O2's also allows you to run leaded fuel, if you care.

 

all you would need to do is weld a sleeve thru the jacket with the proper threaded insert on one end for the O2 sensor

 

As long as it is before the exhaust riser.

 

well how do the ski boats using inboard ls1's work it? regardless could always run dry exhaust, depending on how it's routed (i.e. not through transom) most the olds/berkley setups run dry exhaust I believe.

 

placement would be irrelavent (to a certain extent), but would be more favorable closest to the cylinder head

 

If its after the riser I believe it would give false readings. The riser puts a LOT of water into the exhaust.

You could only do dry exhaust if you have an open engine bay, and the headers go over the transom. You need a muffler then though (water in the exhaust is considered a muffler).

Your O2s would hardly ever get used though, usually when cruising in a boat, you are in PE mode, ignoring the O2 sensors anyway.

 

you're absolutely right, I thought you meant riser extension not the riser elbow...it would definetly have to be well before the riser outlet into the exhaust as the water would kill the O2 sensor in short order


PE entry could be tailored to prevent premature calculation entry

 

here's an option but a dry setup it looks like

 

Merc has been running SD tunes and no O2 sensors for years;
https://ls1tech.com/forums/pcm-diagn...2-sensors.html

 

True, but on most boats I've seen, the elbow and riser are 1 piece.

Those end up to be around $1K or more after they are shipped from Austrailia.

Here is a cheaper option:
https://ls1tech.com/forums/conversio...manifolds.html

The manifolds are about $250 each and are the same for left or right side. The risers/elbows are about $150 each.

 

Aother option, 351 cleveland manifolds, I've got a pair, cheap but not always easy to find.
https://ls1tech.com/forums/conversio...ttom-boat.html

 

Nice find!

Here is the PCM manifolds a little cheaper
http://www.skidim.com/prodinfo.asp?number=R028023

 

How would you weld the inner side of the manifold for an o2 bung?

I want to EFI my volvo/penta 280 by using an old TBI set up and megasqirt. I would run it speed density but need my wideband for initial tunning.

How else could I tune it?

 

welding would be the tough part, unless you have extension between the riser and manifold that's easier to get to. I have a set of Moore Performance alumium manifolds on my 350 in my boat, they have a 1/2" NPT port in the manifold for an external EGR crossover. If you had something like that it would be easier.


The area circled in red is the EGR crossover port

 

Could you do it with the boat out of the water? Just jimmie up a temp exhaust manifold with the WB in that.

You could also take the motor to dyno shop and get a first class tune.

 

have to tune in the water to load the motor for proper fuel scheduling/timing

 

another option, little pricy tho



http://howellefi.com/customer/produc...cat=285&page=1