Hi,

Found what appears to be a good deal on a 3 circuit 1150 Dominator, for my set up but I'm not sure if going the 3 circuit route is right for me. List number 9377, so its an older 3 circuit, with no PVs.

My boat is an 89 baja force 235 that runs in the mid 60's at about 4700 rpm with a 24p bravo1 prop at about 6500 ft elevation on Lake Abiquiu in New Mexico

Motor is 8:1 compression 454 with a B&M 174 running 7.5 lbs boost at WOT
Cam specs are,
238 int./248 exh. @ 50
540/540 lift.
114 LSA

Current carb is an 850 boost referenced vacuum secondary with 3.5 PVs. Reason I feel it's far too small is that I ended up having to increase jets from 78 primary/82 secondary all the way up to 97 primary/98 secondary before I got rid of the lean condition at WOT.

Anyhow, I know merc ran a 2 circuit 1050 with 6.5 PVs and some pretty fat jets on the 525SC and it seems to me that I should maybe just copy them....At this point, I've been going back and forth with this guy on the carb and I'm in uncharted territory with the whole 3 circuit no PV thing but I hate to turn down a good deal....

Any advice towards 3 circuit carbs on top of small blowers??

Thanks,
Travis

Stay Away from the 3 Circuit , complete pain in the ass to tune. And with out power valves that thing will eat fuel.
You probably had to go richer to cover the heat made by the blower .

Anybody up on his cam specs?? 8.1 and 7.5 boost should be a pretty decent motor and in my mind at 4700 rpm, shouldnt he have another 4-500 rpm in there?? is the 24 a tad to much prop?

It would be a solid 550hp engine, but he is at 6500' of elevation.

IMO, an 1150 is way too big. Even the 1050 on the 525SC was on the large side.

^^^^^^^^it is almost not posable to overcarb a roots blown engine.

Mike I hear what your saying however I bought a set of pro systems 950 carbs that were built and spec'd for 177 engines. It kinda through me off a bit but I even talked with Patric before purchasing them and his comments were they were perfect for the 177 builds but a little on the small side for my use but would work.

mercury marine would have used a smaller cheaper carb but they spent the extra money for a reason.on engines like the sc525 fuel distribution is not real good but the dominator 1050 helped.the sc525 came with 7.5-1 compression ratio and a whimpy hyd flat tappet cam,without boost it would not get out of it,s own way.the small 177 blower would not move enough air with a 4150 carb,it made less than 500 hp so the dominator was the answer.

3 circuit carbs are designed for drag race cars using a trans brake where there is no accel pump shot left on starting line leave

Pro systems built me two 1150 dom carbs last year. 3 circuit. He had the intermediate circuit very soft. Power valves were the high flow style (I had a ton of PVCR). Clean idle, clean cruise (around 13.5), just a hint of fattening up when the PV's opened. Otherwise they were perfect. I monitored via O2's...I quizzed him on the 2 vs 3 circuit debate in marine. He laughed and responded that it's 2016. Old days are well past us... FWIW they can and do work. [ATTACH=CONFIG]563200[/ATTACH]

Thanks, I've seen this response a fair amount regarding 3 circuit carbs and it seems to make sense to me from what I understand about how the intermediate circuit works.