Will your twin powered boat plane on 1 engine?

[Trav4011]

Back-in-Black - 1/26/2008 11:41 PM

25 Contender with twin 250XS. I'm runing 24" Bravos now and it won't plane on those props with 1 motor. When I first put these motors on I was running 23" Mirage+ props. With no wedges and full fishing load with 4 guys, up on plane fairly easy. The only problem was getting out of the water without the props blowing out. Once up, how fast you wanta go? Could run 35 mph at about 3/4 throttle. The blowout problem was why I went to the Bravos. The Mirages would blowout while up on full plane with both motors.

I'm having my Mirages tweaked so I can keep them in the boat for emergencies. I also have wedges now, so hopefully getting up won't be a problem. As far as overloading my one engine... why would you think that? I've seen this exact same boat for sale, factory rigged with single 250's, so why would running my boat on a single 250 be stressing it?

That's exactly what I'm doing.. I'm putting a pair of 225 opti's on my 25' Wellcraft.. which is way more power than what it's rated for. But, I want the ability to cruise at 40mph @ 3500rpm, and run in on one engine at 40mph if I need to..

[boats742]

Buddy of mine had this happen to him with his brand new 38 Fountain with tripple Verados...........

his middle engine goes out 60 miles offshore due to a "computer problem"
He figures no problem, he will come in on the other two......he did it during the sea trial
Boat would not plane with 6 guys, gas, Ice, gear........
Gets home at 2 AM....not happy............

[jfwireless]

My Hydra-Sports 2390 can get up one engine using the 175 Ficht, now that I have just re powered with a pair of E-TEC 175's I haven't tried it yet. My guess is if the Ficht could do it , than most likely the E-TEC with more low end torque will too.

The reason I stayed with a 2 stroke is to be able to get up on one engine, and take advantage of the lower weight of the engines. If I had put a pair of 4 strokes on the back the added weight and loss of torque would most likely make it impossible to get up on one engine.

I have been out 30 miles a couple of times and came back one engine at 30 MPH with the Ficht 175, didn't really bother the Ficht. Of course one of the reasons I repowered is so I didn't have to do that anymore.

The Ficht engines had lots of power and liked to run near the top, idling was their issue, and keeping them running. I had lots of little issues with them like oil pumps, coils, just could not keep them running. But running them hard did not bother them at all, if fact I think it helped keep the carbon down, their biggest problem.

Jim

[saltfever]

We have a Polar 23CC with twin F-115 Yamaha's. We can plan on one engine at 26 MPH. We had one engine shut down just past the sea buoy out of Lockwood Folly N.C. with 150 gal of fuel and 2 people, she got up and came back in with no problem.
This is why I just can't go with a single engine past the breakers. Most dealers and boat buillders are not considering twins on most boats under 24' because of the relability of the four strokes.

[jethro1]

ClarkLLC - 1/26/2008 9:30 PM

Plane with one engine or no plane...........the one instrument that you probably do not have on your panel...
MANIFOLD PRESSURE.........yes you will plane a boat with one engine in some cases or not...either way ....you are
pullling down the good engine and really looking at a serious problem with the good engine in the future by putting
that much stress............any pilot will tell you...single aircraft or twin....power up and climb without watching the
manifold pressure .....is trouble looking to happen..................twins on a vessel....and have a motor go down...
and ask the good engine to respond and put you on plane....is asking to much of a piece of equipment that is not
rated to run in such conditions (weight/speed).......I have lost an engine off shore....but took my time coming in
being concerned of the stress that the good engine is under.....

Most don't/won't/can't get it. One comment above related manifold pressure to superchargers. How silly is that?

The engine makers need to start installing instrumentation that captures manifold pressures and RPM's. That way, they can see if a motor is over propped or if a twin powered boat has been run on one motor and void the warranty if this is the case.

[flukin nuts]

272 grady with 2 225's. Not even close. Tried it once.

[2550 Pursuit]

CaseyP - 11/9/2007 5:23 PM

25 pursuit with twin 200s can plane on 1. Needs tabs and have to lift the dead motor out of the water. With the motor down, no dice. Tops out at 4500 RPM.

Same boat but with tired 225s without tabs, not a chance. Had to try 3 times in the last 30hrs of running time.... BTW, what make motors do you have and how many hours? Im curious how sorry and tired mine are. At WOT I can do 40kts, what can you do?

[DoneDeal]

On the surveyors sea trial last wed. he asked if my 25 seaCraft with twin 200's optis would plane on 1 engine. I had no idea so we gave it a shot, leaving both legs in the water. With 19p rev 4's, the thing jumped on plane and got to 4900 rpms with no trim and the corrospnding leg still dragging. I was shocked, we were running the icw at low 40's. Would have been good to know when offshore but never needed to find out.

[CapnDean]

Twin Vee 26' Weekender twin suzuki 115's will plane with one out and one in. Full load of fuel, no ice, 4 passenger. I tested this on purpose and it worked with either engine trimmed out. That being said: I concur with Jethro somewhat. If I lost one engine and was 60 miles offshore would I plane all the way in on the one engine? Probably not. Would be safer to travel displacement speed (unless it was rough..TV Cat's ride safer on plane). IDEALLY: I would keep a spare prop handy that had 4" less pitch for this precise situation. Typical outboard (2 or 4 stroke) is NOT designed to LUG for long periods. That is why we all strive to properly pitch our props.

[GWcpa]

Grady White 232, twin 200 HPDIs, 19" Mirage + props, no problem. Pull back the throttle and run at 24 knots, max around 30 knots.

[Gvit]

kaneroy - 11/9/2007 4:18 PM

tried once ,not a chance. and the boat is maxed in power and will run 60.

Same boat, same power (23 Contender, 200 hpdi's), same results.

[RUDE Attitude]

No chance with the 200 hp 2.6 liters and 19 pitch props that seem to gie best performance in double mode.

I now carry smaller diameter props for each motor, 14 1/2" x 15 x 3, and have tested both motors in single mode. 5300 rpm at WOT and 27mph.

[The Pig]

My Edgewater 245 with twin small block 200's will easily plane on on engine and tops out at about 33 knots.

[The Pig]

My Edgewater 245 with twin small block 200 Etecs will easily plane on on engine and tops out at about 33 knots.

[darbikrash]

jethro1 - 1/27/2008 6:08 AM

Most don't/won't/can't get it. One comment above related manifold pressure to superchargers. How silly is that?

The engine makers need to start installing instrumentation that captures manifold pressures and RPM's. That way, they can see if a motor is over propped or if a twin powered boat has been run on one motor and void the warranty if this is the case.

I'm nut sure I understand how to relate an engine overload conditon to manifold pressure if the engine is naturally aspirated. Can you help with this?

Naturally aspirated engines by definition can see no more the 14.7 psi absolute or 0 psi gauge pressure. Most gauges read in, well, gauge pressure so all we really see is vacuum. (0 psi gauge) which is more typically callled boost. Even boost by itself does not tell you that an engine is overloaded, just that is is under boost. As maximum boost is usually regulated by either a waste gate or electronically, the fact that an engine hits maximum regulated boost (as seen by the boost gauge) in and of itself does not tell you that the engine is overloaded. Running at max boost is a duty cycle issue, not an overload.

Aircraft engines are for the most part turbocharged, and pilots use manifold pressure as a means of expressing % power output indepedent of altitude, which is important for reasons of air density. Turbochargers (but not superchargers) are decoupled from air density, as they just spin faster and compensate for the decreased air density by increasing the volume of air flow.

It is my understanding that another piece of infomation is needed to determine overload, and that is EGT. Another way of saying overload is lugging. The classic definition of lugging is when the EGT is RISING and the boost (manifold pressure) is DROPPING, which will quickly create a runaway heat cycle and fail engine parts in a hurry.

Not sure this works if all you have is manifold vacuum on a naturally aspirated engine.

Isn't the vacuum gague really just showing you throttle position on naturally aspirated engines?

[CapnDean]

Darbik: That's why I agreed with the caveat "somewhat". It is my understanding that the 'manifold pressure' warning was simply a chap expressing his fear of lugging & or overloading. True we do not do manifold pressure on outboards as they are naturally aspirated. Yes EGT would be a better indicator but for the most part you can look at your tach and tell. E.G. Throttle is firewalled and the tach is -1000 rpm from normal. Houston you got a problem.

[kerno]

jethro1 - 1/27/2008 4:08 AM

Most don't/won't/can't get it. One comment above related manifold pressure to superchargers. How silly is that?

The engine makers need to start installing instrumentation that captures manifold pressures and RPM's. That way, they can see if a motor is over propped or if a twin powered boat has been run on one motor and void the warranty if this is the case.

Well, I guess I just don't/won't/can't get it. I've written books on high performance engine design and I drove blown gas hydros for many years and here I am, lost. I am pretty familiar with a manifold pressure guage. Gee, I even have one in my F-250 diesel. If you can make true (above ambient) manifold pressure without a blower or turbo, I'd like to see it done.

The comment about engine makers needing to put in software to babysit our boating is interesting, at best. Here's a fun scenario: We're cruising along at 1200 and nail the throttle. The rev's are still down, but the throttle is open. The engine load is high and "OH NO!!!!!!! The manifold "pressure" approaches atmospheric and suddenly the engine warranty delete lights up.

If I may ask, Jethro: If you have an outboard powered boat, does it have a manifold pressure gage on it? As an alternative, have you ever seen a manifold pressure gage on a naturally aspirated outboard boat?

[wigsplitter]

Mine will get on plane with one motor no problem

[ABiggrBoat]

My Robalo 24' CC has no chance with twin Yami F150's. I've tried it several times.

Steve

[ul412al]

2500 Hydra Sport CC with Twin 225 Merc EFI's. It will do 40mph with one engine. Use the trim tabs and the hole shot is pretty respectable.