Everyday it seems I am getting closer to bagging my search for a performance CC and returning to the Formula family. Yesterday I went boat shopping and have come across a nice higher hour (689) 99 312 Fastech with 454 MPI's (one motor (has approx. 150hrs) and both gimbals just replaced) and a really nice 95 252ss with a 454 MPI B3 (pretty much all new powertrain). I like the idea of getting into a twin engine boat again. The 312 was pretty impressive having not been in one of the newer boats. It seemed like there was more cockpit room than in my old 1990 292SR1 (even though they are both 31'). So, I did some surfing last night to see what kind of performance data I could find on the 312. I found an old "boattest" report but it did not list the year. However, the test was done on a boat powered with 454 MAGs (385hp). So, it had to be of similar vintage. The report said it topped out at 72mph and best cruise was at 40mph turning 3,000rpm. The interesting thing was it said that the boat logged 14.6 gal/hr or 2.75mpg at that cruise rpm!!! What? does that sound right? Do any of you all have any data regarding cruise/GPH etc? I know that a twin big block boat is gonna use fuel. But, if that Fastech hull design is that much better than the old SR1 stuff, than I am going to step up my game and look for a Fastech!!!

those numbers could be correct if you're willing to ride around at 3,000 rpms (I never was!) The boat you listed is also a 310hp version so the speeds will be much slower and the fuel burn likely higher (to achieve the same speeds)

BTW: My old 312 had 502's and 72 GPS was my typical WOT speed with rare runs to 74......I figure that old test you found showing 72 was it's best speed on it's best day. The 310 hp boat likely does 65 tops.

FYI, here in SW Florida along the Caloosahatche River (the ICW), there are speed limits (believe it or not). Plus, to get to some of the cool spots here, I would most likely "cruise" most of the distance and not be WOT. So, that is why the cruise RPM, speed and fuel consumption was of note. Heck, 14.6 GPH @ 40 mph is like what I would expect from a 26' Sea Ray bowrider with a 8.1 or 8.2 in it ! Also, it was similar to what I was expecting if I was able to get a 30 performance CC with outboards.

There is another 312 here for sale with a pair of 350 mags. Those are rated at 300 while the 7.4 mpi's on the other I looked at are rated at 310. With the weight reduction of the small blocks and the ability to turn more RPM, wouldn't that be a similar or maybe better performer than a 7.4 MPI boat?

also, with the 7.4 MPI, wouldn't the performance be the same (or similar) up to like cruising speed and then the hotter cam and heads of the MAG motor would come on hard after 3k rpm (or so) and leave the 7.4 MPI guy behind?

The 350 would have less torque and turn a smaller prop than the 310 horse 7.4, although to higher rpms. Top speed would probably be similar at low 60s with the 7.4 being a couple mph faster. But at a cruise the 350s would be slower for the same rpm because of the smaller prop.

A rough check on my 311 showed about 20gph at 38 mph cruising up the maine coast about 200 miles

my 98 312 will run 72mph all day everyday and in the right conditions has touched 75mph. twin 502 mag's

Those 25mph zones down there are killer down there in SWFL....had I not put the longer tabs on there would be no way I could stay on plane below 30mph. I can keep her up at 26.8mph now but I know I'm not being very efficient fuel wise. I definitely feel out of place down in SWFL as we were just there for 2 weeks and didn't see another performance boat the entire trip. Def in the minority down there I feel. The last few years of the 312 you'll see they switched over to the small block 6.2s from the 7.4s Similar amount of power in a smaller footprint. I have 350s in my 292, best cruise is right around 3300-3500 at like 38mph. She just dials in real nice and has a nice smooth ride almost effortless at times you just get that feeling that this is where she likes to be. I also get more out of a tank if I keep her in that range. Sometimes I can bump her up to 3800rpm and cruise 43-45mph, you'll notice that full tank will disappear a lot quicker in that 3800-4000 rpm range than if you were to just back off a bit.

[QUOTE=Splitdecision271;4513888]Those 25mph zones down there are killer down there in SWFL....had I not put the longer tabs on there would be no way I could stay on plane below 30mph. I can keep her up at 26.8mph now but I know I'm not being very efficient fuel wise. I definitely feel out of place down in SWFL as we were just there for 2 weeks and didn't see another performance boat the entire trip. Def in the minority down there I feel. The last few years of the 312 you'll see they switched over to the small block 6.2s from the 7.4s Similar amount of power in a smaller footprint. I have 350s in my 292, best cruise is right around 3300


Yeah. I spoke to the marine patrol about that because my old 292 didn't like going under 30 either. I explained that if I was expected to run at 25, then the boat would sit WAY lower in the water thus causing more potential harm to the Manatee. They agreed and just said keep it reasonable. I never had an issue with the speed limit.

I really like the 336 for sale across the state. But, after seeing and reading the reviews about the fuel economy on the 312, that really peaked my interest in the Fastech design. So, now its back to the drawing board. I'm sure if I wait much longer , the 336 will be sold and that will make the decision easier, lol.

Here is a clean looking boat albeit a 303 SR-1
https://loz.craigslist.org/boa/5924144541.html

[QUOTE=GLENAMY 242SS;4514057]Here is a clean looking boat albeit a 303 SR

Thanks! That is pretty nice. Although, as I expand my search, it makes me a little nervous buying a boat from up north this time of year because its usually too cold to really run the boat long enough to make sure there are no cracked block issues etc.