Thank you for the interest, actually I had a couple o2 sensor codes so I replaced them all and they seem to be working fine now however, I was in the process of trying to eliminate the o2s purchasing that o2 eliminator box as well as exhaust manifolds to remove the cats and everywhere I was reading they said to call whipple they can do some custom tuning to the ecu or there was one other guy to build tunes as well. So I figured If I could do the exhaust manifold maybe a set of heads, larger injectors, cam etc however when I spoke to the rep at whipple he told me Mercruiser slapped them with a law suite and until they work out this issue they are no longer capable to do any tunes nor will anybody else on these black model engines without getting themselves in trouble as well. basically they were making as much power as the 525 with exhaust, new throttle body, and a cam so i'm thinking they were taking $$$$ out of Mercruisers pocket not to sure. But sucks for our stock engine weekender.

They use the same computer module, and Edlebrock suggested I could upgrade the intake to the XT if I wanted to. they are wicked cool looking too!

jdr

Ordered a pair of the bung extensions. Ill let you know how they work out. May not know until next year as Im replacing my Bravo 3s with Arnesons. Rooster tails for next year!

So I got the bungs today! man these are not junk, but really well made. they indicate their use as being for high temp usage such as turbos, and other power adders. Bbut it makes sense given the design tht these would work really well in keeping water from getting to the sensor.

More to come as I test!

What brand/model did you get.
I need to look into some. Figure how to put on some fairly new Eddie Marine elbows that dont have a bung.

THESE are what you want, I was tuning a twin with lightning headers, was only thing that would make o2s last more than minutes. I tried them on my dyno and in boats, there was no diff on dyno in afrs or response time, directional, they keep water off o2s great! not cheap but well worth it
https://www.ebay.com/itm/27498899266...iABEgLQBfD_BwE

I had a local guy weld the bungs in. Not cheap, but I could not find an adapter for my NoS Smooth side Gils headers. Hardin does have some good options here though:
https://www.hardin-marine.com/c-391-o2-sensors.aspx
-jeff

I’m just going to keep this as the shortest post so far I feel. If I had Smitty tune it and I had issues, I’d reach out to him and resolve the issue as he’s a very sought after tuner and customer service is second to none before I blew his name out as working on it then looking for internet ideas. Just a thought.

Chad, tune wise, on the water the afrs were pretty close to target, we dialed them in even better. So both motors have right timing, afr's, fuel press etc yet one pulls much less rpms and lags behind the other one hence OP "snorunners" post. He has also swapped all the efi components from one motor to other with same motor still not pulling rpm. At this point Im confident its NOT in the tune or injectors I provided, If it was up to me, that motor would be out of the boat and getting dissected or dynoed, smitty

I didn't read this whole thread but has the OP swapped props?