40 hp Merc

[Rick-D]

I have had nothing but trouble with this Tohatsu 50 hp power engine. Long story short spent about 1000 dollars by two different authorized dealers and still keeps doing the same thing. I am looking into getting a 40hp merc and was wondering how this engine would perform on this boat. Was wondering if would be giving up a lot of speed going 10 hp less. Would appreciate any advice.

Thanks in advance.

Rick

[Rick-D]

Sorry, forgot to say that I have a 1997 macgregor 26X, and I believe the engine is a 98. Reaches 4000 rpm and bogs down to 2200. Will run at 3000 to 3500 rmp steady and that's it.

Thanks,

Rick

[mastreb]

I seriously doubt 40hp is enough to get completely on a plane, which means you'll be limited to about 9 knots, be very inefficient, and somewhat dangerous in plowing mode.

[Ormonddude]

I have a alarm go off on my 40hp yamaha, I am going to check the prop specs you may want to do the same - this is a cool little prop calculator even if you dont buy from them -
http://www.philspropshop.com/index.php? ... ry&path=89 in case it takes you to the home page click the prop wizard and enter your information only other thing I can offer is make sure the breather is open on fuel tank

[c130king]

I have a 40-HP Mercury 2-Stroke. I think it is a great engine.

No ballast and no wind I can get 15 knots with just me. 14 knots with two folks. Not sure about if it is "on a plane"...don't think so...don't really care.

Somewhere between 3 and 4 gallons per hour at full throttle.

Cheers,
Jim

[Divecoz]

Are you buying a New or a Used Mercury? 2 stroke or 4 stroke Standard Prop or Big Foot EFI or Carbs?
Ball Park Numbers? I get depending on wind and waves, 15=18 MPH Full Ballast moderately loaded with my 50 HP EFI Merc Bigfoot / 14x10 Prop..

[Rick-D]

It is a used 4 stroke merc in great condition. Still may be leaning toward a 50 hp or even a little more. I do a lot of fishing and need to go about 15 mph. New motors are just so damn expensive and they don't last. I have a 25 hp Johnson on another boat from the 70's runs like a top. I had a 18 hp Evinrude from the early 60's and started first time and ran great, until somebody stole it. It just seems things are so expensive anymore and don't last.

Thanks for all the advice.

Rick

[Seapup]

It is a used 4 stroke merc in great condition. Still may be leaning toward a 50 hp or even a little more. I do a lot of fishing and need to go about 15 mph. New motors are just so damn expensive and they don't last.

My father in law has one on his 16' bass tracker, bought it new about 10 years ago as a package and has had zero issues with it. He is very happy with it. I have run it a few times and it is very smooth and quiet. For his boat its a nice match. With only two people on it it scoots, but with 5 it won't get on plane. I doubt you would see 15mph on an X unless you were running a completly stripped hull.

Not sure where you are at and what price you are looking at. I wached prices for awile before swapping 50 to 90. In the south east there was usually only $500 or less price difference between similiar year and hour 4 strokes.

[mastreb]

I have a 40-HP Mercury 2-Stroke. I think it is a great engine.

No ballast and no wind I can get 15 knots with just me. 14 knots with two folks. Not sure about if it is "on a plane"...don't think so...don't really care.

Somewhere between 3 and 4 gallons per hour at full throttle.

Cheers,
Jim

At that speed, you're definitely planing. So retracting my doubt!

[NiceAft]

Rick,

You peaked my curiosity. What happens at 15 mph when fishing Will 13 or 12 mph work

According to Jim, You should be able to achieve your goal. Actually, he says he can do 17mph.

I don't believe an will plane until it hits 20mph. I've had mine close to that, and it was not on a plane. (To all Mac board members, please refrain from airplane/Mac jokes ) I don't know what the planing speed is for an , but I would not be surprised if is about the same as an .

Ray

[RobertB]

I don't believe an will plane until it hits 20mph.

I believe the and other similar boats are technically on plane when they go past thier displacement speed of about 6.5 knots (1.34 times the sqrt of the waterline length).

[ualpow]

I have a 30hp 2002 Merc 4 stroke EFI on my 2000 It was on the boat when I bought it. It is identical to the 40hp except for the air restrictor and ECM programming. I had the ECM reprogrammed and removed the air restrictor and I get 10.5 knots full ballast and 13.4 knots empty ballast.
If I had to buy a new/used motor I personally would go with more than 50hp just for the reserve power if I had to push through some heavy waves.

[mastreb]

I've had mine close to that, and it was not on a plane.

You were definitely on a plane at that speed, although a much wetter one than a bayliner would have been on at the same speed. Macs are "semi-planing" hulls, which means that while they get on a plane, the hull is not optimal for planing so its quite a bit wetter. In the specific case of Macs, and more especially the X, the stern is flat like a planing hull and the front is deeply Veed like a displacement hull. Once the bow is completely out of the water, the boat is planing.

There are three "modes" of movement through water:

Displacement: (nearly no wake, high efficiency) From standstill up to the "hull speed" of the boat which is 6.4 knots, all of the water through which the boat travels is displaced around the hull and there is little to no wake. The boat pivots through the water on it's daggerboard and requires large rudders to steer. A significant bow wave is not present.

Plowing: (Maximum wake, minimum efficiency) Beyond displacement speed, the force of the boat through the water creates a bow wave. The bow of the boat raises as it climbs this wave, but there is not yet enough energy to push the boat up over the the bow wave. The boat is between displacement and planing modes. Stability is compromised because the boat is both pivoting and side-slipping, and very inefficient because the energy of movement is going to creating maximum wake. There are boats designed to travel in this mode called "wake boats" so that they create wakes for wake boarding skiers. Their hulls are designed not to get on a plane, and they have a hull shape and control surfaces designed to handle the plowing mode. On an empty Mac X, this mode is dominante between 7 and 12 knots. On an empty Mac M, it's between 7 and 14 knots by my calculations (which are based on fuel economy at different speeds). This is why an X can get away with a smaller motor than an M.

Planing: (less wake, moderate efficiency) Once the boat gets up over its own bow wake, It's on a plane. Control is no longer performed by pivoting but by sideslipping and rotating into (rather than out of) corners. Efficiency improves dramatically because the boat is mostly out of the water and not creating as large a bow wave or wake. That said, the more your boat weighs, the more power is required to get up on a plane. Control surfaces under the water must be very small so as not to limit the boat's ability to pivot into a turn, which causes dangerioius instability.

You can determine when you're planing by watching the fuel efficiency of your motor sensor. Once you're on a plane, efficiency more than doubles on my boat. You can also see it by measuring how far back your bow wave is being generated.

Granted, on an M it never really feels like you're on a plane because of all the spray, but you are.

[NiceAft]

I have been educated

Ray

[Divecoz]

Actually Rick.... These new outboard last for ever, when used and maintained properly.. I say that having First Hand Knowledge and having spent a lot.... of time associated with the Tourist Dive Destination Of Cozumel MX. That Said .. Anyone who knows anything about motors knows that letting them sit for months and months is the worst / hardest thing you can do too them..

New motors are just so damn expensive and they don't last. . It just seems things are so expensive anymore and don't last.

Thanks for all the advice.

Rick