OB on PC's?


H

HellRaZoR004

New member
Anyone think this will happen in the next couple years? With the massive 430 at 26,000 lbs, I would think at face value the PCs could do it. To be honest the OB's are starting to grow on me even though you sacrifice the swim platform.
 
It looks like all of the downeast boat manufacturers are now doing it: MJM, Back Cove etc. Someone even told me that the all might Hinkley has OB power now. So, yea it can happen. If designed like the 430, you don't give up swim platform at all, just stern access to the swim platform. I have far more swim platform than I did on any of my SRs or my 330 or 400ss. But if you have to bunk dock that requires a stern exit or want to carry a dingy, well that is an issue. Take into consideration the 430 is 26k and runs in the mid 60s, and maybe a 34-40PC only needs 3 OBs to run in the 40s and you just opened up some access if Formula extends the swim to the port and starboard side of triples?
 
I am not sure the noise is the downside. If memory serves, my 370ss with 496s was a lot louder than my 430 is. The 400 with diesels was very quiet but it was running only 2700 rpms. I am very curious what the actual DBs are of the 43 with quads at 4-6k rpm? Without any data both my wife and I find the 430 to be easy to have a conversation on at 30 mph in 2-4' seas. We just did this on Wed and were talking about how quiet it was.

I can tell you this, on the dock or putting around a cove, these Mercs are crazy quiet. I have a CC with Yammies that is louder for sure. The gas dock girl didn't know my engines were running.

As for fuel burn - nothing can compete with Pods and diesels. They are faster as well. Next is any diesel. After that OBs should be better apples to apples. They run very efficiently and that is a big reason why they are becoming so popular. My 320 Edgwater CC is getting 1.4+ MPG with twin 300 Yammies w/a fuel burn in the teens to low 20s. My 400 with D6s was very efficient at 1.2+ mpg and a mid 20s-30s gph burn. The 430 is a LOT heavier boat (8k lbs more) than the 400 with a foot wider beam - I am generally seeing .7-.8 mpg but with a burn of 50-60gph depending on how hard I run. Still learning best trims, etc to maximize that. I think this was in line with my 370 with 496s.
 
I could see OB's on smaller PC's (31/34 and smaller) because of their corrosion resistance in salt water and better efficientcy compared to gas I/O's. In larger PC's diesels with pods make more sense to me.
 
Just did a quick on line search and found the following according to BoatTest:
Best cruise DBs for the 430 with quad 400Rs was 77
Best cruise DBs for a 400ss w/ D6 Volvos was 83
Best cruise DBs for a 370 496s was 88

OBs were quieter.

Fuel
Best Cruise 430 ssc 42 mph .7 mpg 50 gph 327 miles at 5k rpm
Best Cruise 400 ss 38 mph 1.5 mpg 26 gph 328 miles at 3k rpm (D6 Volvos)
Best Cruise 370 ss 36 mph 1.1 mpg 35 gph 277 miles at 3.5k (496s)

At or near WOT
43 64.2 mph 154 gph (wtf??) 187 miles 7k rpm
400 47.2 mph 41 gph 259 miles 88 DBs 3590 rpm
370 54.3 mph 75 gph 166 miles 92DBs 5k rpm

Having had both a 496 370ss and 400ss w/diesels that is pretty close to my real world experience.

Net, the OBs are quieter even though there are 4 of them. The 430 is 26k lbs with a top speed in the 60s. Not an engineer but if you put only 3 of them at 1200 HP on the back of a 40/37PC I am guessing you get a quieter boat with similar fuel burn, gph etc as a 496 powered boat. But it should be faster at 1200 HP. It would seem twin 400s would be enough power (800hp) and then you get a boat with similar speed and fuel burn but a lot quieter. That should also help solve some of the swim platform issue as you could design one that comes out along the OBs like the Pursuits have. Of course I have no engineering experience but I did stay at a Holiday Inn Express last night.....
 
I wouldn't have expected the fuel consumption to be that much higher on the 430 even through it has 4 x 400 OB's. I looked up the 350 CBR on Boattest.com with 3 x 350 OB and while not quite apples to apples compared to the 370 SS (2' shorter, 3" wider beam, 190 more total HP, and non-FasTech hull) it did have slightly better fuel efficiency (1.2 mpg) compared to the 370 SS w/496 HO's.
 
generally OBs have terrific fuel consumption. Its a 26k lb boat vs 16k and 18k lb boats. That is a LOT more boat to push. Even a 40 PC is almost 4k lbs lighter! And its 4 motors pulling on that fuel plus they are 400Rs. Probably an apples to apples would be the 525s on a 400 or maybe 300s or 350s on a 430. Also the WOT number is extreme - realize at 49 mph I am pulling 73 gph and .7 mpg. That is right between a 370 SS 496 top speed and a 400 D6 top end - and pulling the same GPH as the 496s. BUT it is 10klbs heavier, 1+' wider beam and she still has almost 20 mph to go. I'm guessing the twins would be enough to push a smaller PC with similar performance and better economy. I can't see why triple 300s or 350s at 900-1050 hp couldn't move a 37/40PC all day long. We live in an interesting world for boating innovation so it will be interesting to see. I will say the big issue for the PCs is lack of a tender and swim platform access. I don't need a tender so that isn't a big deal but I am very curious to see how I am going to deal with the first time I am asked to tie up to a bunk and get on or off the boat.

As for pods - I'm a fan. But having owned pods, joystick I/Os and joystick OBs. The joystick OBs are easier around the dock than the I/Os are. Less clunky and more responsive. Much closer to the true pod experience.
 
This is an interesting discussion; one thing to keep in mind when comparing the weight of the 430 to current I/O models is that it's only available with O/Bs, so presumably the weight of the Armstrong bracket is already figured into the equation.

In the Boattest review of the 350CBR O/B boat, they point out in the article that it weighs about 7,000lbs more than the I/O-powered 350CBR due to the engine brackets (and one more engine). In fact, I think they put that sentence in bold because it's rather significant.

I'd have to think a 40PC w/ 3x O/Bs and the hardware to support them would come close to the 430 on the scale.
 
7k additional lbs - HOLY SHIT! That is nuts. The OB only weighs 700lbs. Guys talk about not being able to put a wave runner on the swim platform without altering the running attitude or damaging the swim - how the hell do you add 7k lbs mostly to the stern of the boat? WOW.

Regardless the engines have to move that weight and that has to account for a huge piece of the lose of efficiency.
 
Just took a peak at the Formula site - they only have a 400lb difference between the I/Os and the 3xOBs. 13470 vs 13850 lbs. If that added 7k lbs according to the BoatTest, what was the total weight? The I/O is 13k lbs - I cannot imagine the 350 comes in at 20klbs? Not sure which is accurate (its online so they both must be true right?!?)

Interestingly, if the factory site is correct and the 350 Merc weighs just under 700lbs, then the boat with is actually lighter with OBs and the bracket if you only had twins on it. A quick search tells me why - 496s weigh 1100lbs and that does not include the outdrives. So OBs are a lot lighter.
 
Just took a peak at that 350 BoatTest - definitely something wrong there. I see the line you did '6k lbs heavier' but then in the data section it has the boat at 13k and change. I think that was a typo and should have read '600 lbs heavier'.

For our original thread's purposes it does compare top end and fuel burn in 350 OBs, Ilmor and Merc 496s. Basically says they are all very close in MPG/GPH despite the 300 hp difference. It also did state that the OBs were in fact the quieter option as measured by DBs. A quieter, faster PC? Seems like they have to be thinking about offering an OB option.
 
boatweiser said:
Just took a peak at that 350 BoatTest - definitely something wrong there. I see the line you did '6k lbs heavier' but then in the data section it has the boat at 13k and change. I think that was a typo and should have read '600 lbs heavier'.

For our original thread's purposes it does compare top end and fuel burn in 350 OBs, Ilmor and Merc 496s. Basically says they are all very close in MPG/GPH despite the 300 hp difference. It also did state that the OBs were in fact the quieter option as measured by DBs. A quieter, faster PC? Seems like they have to be thinking about offering an OB option.
Click to expand...

I agree that 6k is a *bit* much, but there has to be a weight penalty on the O/B looking at WOT speeds:

* 860hp I/O is 56.5 mph
* 1050hp O/B is 58.2 mph

So with 190hp extra, there's basically a 1.5mph gain. The O/B model *must* have some extra fat on her. It does carry quite a bit more fuel, but that's of course a variable weight factor.

(For reference, my 350CBR has 700hp and its WOT is anywhere between 50 and 51.5 mph -- those engines are 300lbs lighter each than the 8.2s.)
 
400lbs is not insignificant so there is some impact there. But when it comes to HP, there is almost never huge gains. I think the WOT on a 430 with 350s is about 2mph vs the 400s. 200 more HP, 2 mph top end.

400ss D6 Volvos 740 HP WOT is 47.2 mph
400FX 525 Mercs 1050 HP WOT is 52 mph

310 HP gets you 5 mph
 
I'm loving the discussion and very curious to see how things progress with the O/B's...they even announced the 400 SSC so the O/B are here to stay.
 
Can someone show me a pic of where the ladder is when you have 3-4 outboards on these things? Even the ladder on my 292 feels like a crappy after-thought, and I've not yet seen these in person or swam up to one.

thanks! Sometimes I think I'm the only person w/a performance boat who actually likes to SWIM...
 
SabrToothSqrl - you don't want to see it. Actually you do as it will make you feel like your after thought is the most brilliant engineering feat you have ever seen! Not sure on the CBRs but on my 430 there is not traditional ladder. I have a stored ladder similar to what you see on center consoles. Its a center post with steps on both sides that is removeable and stored in the engine compartment. Not super convenient. The good news is that it can be used on the port or starboard side. There is also an emergency plastic drop out swim ladder mounted into the swim platform. This is one of the quirks of this particular boat that I cannot really figure out. It seems easy enough to incorporate a real folding ladder similar but it might be that the access hatches for the rigging on the OBs gets in the way. I will try to grab a pick and post it.

The other good news is that the swim platform literally sits on the water. it is super easy to get on and off.
 
that's a shame. If the platform is mostly water level, a slide out step like the ford tailgate would be sweet. You could even do the folding handrail piece. Copy it nearly exactly from stainless and call it a day!

Have you guys seen this: https://www.youtube.com/watch?v=cA3FBBwJt1w

I love the split (dual) shaft design. Brilliant. keeps the torpedo small, but handles the power.
 
If I get really lucky maybe I can re power with twin 627s - I have more HP and all the swim platform I need for a ladder! Picture attached of the ladder. It attaches to a small slit on either side of the platform.
formula_430ssc_ladder_2017.jpeg
 
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