What prop to get on plane on one engine?
 

32 Sunsation Dominator twin 496HO. 6500lb dry.
We plan to do some longer runs to the islands and would like to be able to get on plane on one engine if we had a problem.
Current props are 30 labbed Bravos and runs in the max rpm range.
I have a 24 Rev 4 I will try but if anyone has a suggestion let me know. My buddy owns a prop testing service ;-)

We also may add a fuel bladder.

https://cimg7.ibsrv.net/gimg/www.off...3d2a696576.jpg

I am assuming that you will carry this as a spare and change out if needed. The Eco Enertia has incredible bite and is 3 blade with big surface. Carry an 18 and that should do it.

Joe

Never thought of doing that. Any other experiences with doing this? Probably would work on a heavy boat, right?

tried that on my 28Saber. 650's bravo with imco lowers. Nothing i tried would get it up on plane. no prop would bite and everything just blew out and cavitated.

That`s not happening .


EDIT: It`s happening!!

Join Sea Tow

They will come to you and instruct you to go full gas on one engine and pull you up on plane and run at 25-35. They wont do this on inland lakes and waterways but offshore they will.

Maybe........I think Sydwayz said he could get on plane with one engine on his 37 AT.
Might be possible with a 22-24" 4 or 5 blade prop.

Yep, I've done it several time in different 37ATs.
I ran stock 28 Bravo1 4 blades on my boat, and I know Pat has done it with 30s. You would be better off with a meaty 5 blade for this task, but a 4 blade has worked.

Bury the tabs, and ease the boat up. You may have to waddle the steering wheel a bit back and forth for it to surf it's way up. I've been on plane as slow as 17mph in the 37AT hull with the tabs buried.
I've run as fast as 30mph with only a single screw, WITH the second downed side prop on. Realize, you are putting TREMENDOUS stress on the drive that IS working.

If you "have anything left" with the downed side, it would be beneficial to reduce the torque/weight stress on the good drive to get on plane. The last thing you want to do is break the good side.
I did this once with a drive that was knocking really bad. I used as little as possible to pop the boat up on plane.
I got everything moving and set with the good engine/drive, and started the engine with the knocking drive; engaged forward for a few seconds, just long enough to pop it up on plane. Then killed that motor and trimmed it out.

Taking the downed side prop off is a tremendous drag reduction. But I've never had to do it.

Couple questions to help you get in the ballpark:

What’s the slowest the boat will stay on plane?
What’s typically your cruising RPM?
What gear ratio are you running?

Just got my buddies Formula 330 SS on plane on 1 a couple weeks ago, when we were pulling it for the winter. Does have B3 drives though.
Was also able to get my old Bravo driven 33AVS on plane on 1. It did take a lot of finessing though.

Play with the prop slip calculator on the Mercury site. Just for haha’s I put in these parameters:

1.5 ratio
20% slip
Wanting to achieve 25mph at 3500rpm gives you a 14P prop.

I think it more depends on the boat and its setup. Ive been on and witnessed first had a 2000 38' powerquest with twin 500efi's get up on plane on one engine! Blew me away! But me trying to get my old 1984 30' scarab II with twin mildly built 454's there was no way it would do it! I eve tried to test it while running....ran the boat up to about 30/35mph...trimmed one side up till it was blowing out then killed that engine and kept trimming up to try and get the drive as high as possible....boat instantly started dragging and i'd say in under 30sec it fell off plane...even with giving it more and more power it was either too heavy or the drag of the drive being offset tot he side (TRS) was too much...

Dang, that's impressive. Ever try to surf behind one at 17mph?

Never thought to. But we have tubed behind a 37AT.

I had a drive failure on a Sunday boating in New Jersey on the way back to the ramp. This was our 27' Magnum Sport "the Hairy Canary", with twin 454 cu.in BBCs, TRS drives (raised X-dimension), with 27" Mirage props with added cup and thinned leading edges/labbed props. I thought a transmission on the starboard side failed. At first, with the port drive tucked down all the way and the starboard drive elevated a bit I could not get the boat on plane.

My weight at this time was 200 lbs., and my friend who was 200 lbs., I figured bow weight would make the boat plane, and it did. I had my father put the throttle down on with me and my friend on the bow, the Magnum did as expected, came on plane and we were on our way; the 400 lbs/. of added bow weight allowed the boat to plane and stay on plane as we crawled back to cockpit while the Magnum was underway on plane.

When I thought the transmission had failed I was incorrect, it was a broken prop shaft. When I raised the drive when to see if in fact it was the transmission that had I failed, I would look at the prop stay stationary while my father put the drive in gear, forward and reverse, and there was no propellor movement, and the prop was there at that time - clearly visible before we put the boat on plane. So, the assumption was transmission failure, due to the fact we raced the **** out that boat every weekend.

When we arrived at the ramp and pulled the boat out of the water, the propeller was gone, and half of the prop shaft was gone. The water pressure, force of water while on plane extracted the blue-printed Mirage prop I bought, with the shaft, that was a something I will never forget.

The 34' Phantom with Bravos drives and 34" labbed Bravo props would not plane on one engine (540 cu. in EFI motors), no matter what I tried, no way could we get the boat on plane (water hose burst that day while boating on the Elk River, in Maryland/upper Chesapeake Bay), that was a long idle home to New Jersey that day!

I thought of this before for same reason.
Never did it though.

My guess is:
Way down on pitch, as much diameter as will fit, and as much cup as they can hammer into the blades.

On the way down on pitch part, I’ve seen bent valves from too much load while trying to do same.

As in, WFO nets 20 mph @ 3k RPM, you probably ain’t making it back to dock under your own power anyhow.

One tidbit for thought......is your boat setup with dual (actively plumbed) power steering pumps or the typical Merc setup where one motor pressurizes steering system and the other's pump is just looped to return line and useless? That is how my boat was setup, and both times I have needed to come home on 1 engine, the dang power steering motor died. Without the power steering (and dual external add-on rams) forget about trying to get on plane when your arms aren't strong enough to keep the wheel straight at anything above 2200 rpm (8.2 mph on mine).

just a thought, the steering went out on my boat and I thought if I just had a ratchet strap I could have pointed the boat in the right direction and locked the steering down and gotten myself closer to the dock. Now I've got a ratchet strap in my small tool box.

I wouldn't trust the steering cable/wheel to hold that much force. Would save your arm if you are still easy with the sticks.

the power steering system still worked, I stripped the cable at the helm.

I think something like a 14P would be your starting point..

Got my 33 avanti on plane with 1 454/hp500 clone. The motor deffinatly didnt like it but i was so mad i just hammered down. Took about 2 minutes 😂. Had a 26p bravo1 prop on it

You guys are totally missing the point of this guys post. He wants to carry spare props with the sole intent of getting on plane with one engine. I take that as when he looses an engine, he will take off his normal props and put on the prop that is going to be used to run on one…..

He’s not asking if the boat will get up on plane with one engine and it’s normal props…

lol..

I seldom post, and I wanted to chime-in with a response. Maybe learn from the success of others. I do understand the call of the question.

If it were me, I'd invest in a set of 24P 4blade bone stock Bravo 1 props. (Or maybe 26s)

Good enough to swap BOTH of them on to get you home if you tore up two props.
"Meaty" enough to likely get you up on plane on one, should you need to do so.

Carry an extra couple of prop nuts, and thrust washers. (It would suck to have a prop with you, but drop all the nuts and washers you have into deep water. :D )
If you have the hubs with the inserts, go ahead and carry an extra set of those two (in the props in the box).

What prop math gets you to 24P with a single 496 in a 32 Sunsation? I’m not being a ball buster, just want to know what gear ratio, rpm, and speed you think he would see and what would be easier on the remaining drive train a 24P with the throttle pegged going 40 at 3500 or a 15P with the throttle pulled back spinning 3500 at 27-30???

To me the key to doing this is setting the boat up to run on plane with the least stress possible on the last remaining drive/engine.

I didn't use any math. :D I was just suggesting a prop that has some bite, but not too much so it would have some slip to not overstress the components.

I couldn't get my 37' AT on plane with 2 props, let alone 1. lol
I believe I have a real aggressive X-dimension.

Very interesting idea. I'd be concerned about stress on the drive too. a single bravo 1 pushing my 29 might be ok, no idea how much push before something breaks though.

A couple years ago I blew the upper gear set on my port drive causing to lock it up along with the engine. This was on the second day of a two week boating vacation - bummer... For the rest of the trip we just putted around on the starboard engine keeping it below 16-1,700 RPMs to minimize the stress on that drive. Last day came and it was time to put her back on the trailer. I said screw it, let’s see if she’ll plane on one engine. So with just me on board, half tank of fuel, k-planes buried, port drive up as far as it would go (due to the tie bar), I eased into the starboard throttle. At first it was just a whole lot of spinning and cavitation, but then it started to bite. I got her up to 35 MPH on just the starboard drive before backing it down. I probably took years off that drives life... This was in my Baja 342 with 500 EFIs on a 28P lab finished prop.

Yeah, nothing I did would push mine over 6-7 MPH on a single engine, so to minimize issues I just go home at 6 MPH. Still faster/easier than a tow.