Tahoe540

It currently idles around 950-1000 but after taking the motor apart I have had this thing super rich. I will be putting my 850 Demon instead of the 950 I currently have and see if that helps.

Also, why I am at it I was thinking of changing the the advance on the cam. I have an adjustable timing chain and I currently have it at 2 degrees advanced per the cam card (but that says for 11:1) but I was thinking of retarding it back to straight up 0. My reasoning is for I have plenty of low end torque and would this help with reversion? Any thoughts on this change?

ezstriper

you really need to tune the carb with a wideband, just swapping carbs not going to achieve much most likely, just pissing in the wind

Baja Rooster

iTrader: (1)

If the carb was super rich it can wash the cylinders and the rings won't seal. A different carb won't fix that but different jetting will.

Tahoe540

I have IMCO Power Thumper exhaust on my motor what do you guys suggest for an O2 sensor installation? I looked online and found different options but it looks like most options for my manifold style I would have to drill and tap my manifold which is not an issue. Anyone have a setup they really like?

I don't believe it was that rich to wash the cylinders. It was broke in on a dyno and they said it only needed one or two drop in jet sizes to spot on.

Baja Rooster

iTrader: (1)

I have an excellent local welder that I gave him this link and he welded in bungs for me.

http://www.offshoreonly.com/forums/g...html?styleid=5

The top of the riser at 12 o'clock seems to be the best spot for it.

SB

iTrader: (1)

I mentioned it earlier in this thread. How can these exhausts not revert ? Not all that different from stock Merc exhaust.

Here's a pic for those not familiar with them.

Baja Rooster

iTrader: (1)

I'm no expert, but those look good for about 400hp with an rv cam.

dereknkathy

hell, it's even the standard merc shape where the water comes out above exhaust gas. figure out how long your straight rubber hose is. 2 foot? weld 3 or 3.5 inch stainless tubes about 18 to 22 inch long on the end of the risers running right down the middle of the exhaust hoses. and I agree. doesn't look like anything over 500 tops...i'll take a used set of 496 merc gils over them any day. http://www.ebay.com/itm/Mercruiser-496-8-1L-V8-Exhaust-Elbow-Riser-2-Rise-/202022525417?hash=item2f097b19e9:g:rxIAAOSwVvpZk6U c&vxp=mtr http://www.ebay.com/itm/New-OEM-Merc...lV-yJu&vxp=mtr somebody should jump on those risers. 200 a pair they don't often show up that cheap.

Tahoe540

This is what my exhaust looks like in the boat and I have 19" of soft wall exhaust tubing. Believe me when I first got this boat and was rebuilding it I have been drooling over real headers. This is my first boat and really I am just trying to get this thing right so I feel like it is at its best with what I have. I still want to completely redo my interior this winter and at some point get headers but at this point I can't buy them. I am open to any suggestions to help this system work. I looked into maybe changing the elbows but I don't think anything else would work?

dereknkathy

alum risers? get 3 or 4 feet 3.5 or 3 inch alum tubing. cut back of risers 90 deg from exh hose angle. weld em in. buys you 18 to 22 more inches of reversion insurance. cam you are running now is reverting a little. those manifolds make good power, but need more riser length. hell every boat needs more riser length.