Outboard motor in a direct drive?

[Dacon62]

@GAJ0004 and @EdObermeier commented in another thread (Aluminum slalom boat maybe soon) about a lighter smaller aluminum V6 for improved power to weight ratio. I have also pondered the same thing almost since the day I owned my first tournament boat (1987 Centurion tru trac II).

Why has one of the larger outboard makers not approached a ski boat manufacturer with a direct drive version?

These high tech aluminum block engines are lighter, more compact and have a higher wide open throttle or max. rpm range. Possibly being able to push speeds into the 50 mph range. Important if you also like to barefoot.

Yamaha makes a high tech 350 HP 5.3 liter DOHC 60 degree V8 (W.O.T. 6,000 rpm) that would likely be a little more compact than a regular low tech by comparison cast iron block push rod 90 degree V8 (W.O.T. 5,200 rpm). If you don't need as much power or you have a lighter aluminum hull Mercury makes a supercharged inline 6 with 300 HP (W.O.T. 6,400 rpm). Although I would suspect that the torque would not be there as it doesn't have the displacement at 2.6 liters. Bet that would skinny up the motor box.

 

http://www.yamahaoutboards.com/outboards/V8-5_3L/specifications

 

http://www.mercurymarine.com/engines/outboards/verado/pro-fourstroke/?model=1

[A_B]

I built a 13 foot Glen L kit boat when I was in College, and bought a 750 Honda engine, and my drag bike racer neighbor punched it out to 900cc, and planned to have a little hot rod for the river. Ran out of money, so sold it, and don't know if it ever ran or not.. The thought was aluminum engine, air cooled, and could get wet, high rpms and high hp/weight ratio. I had short stack singles for the exhaust, and it sounded bad ass!

[BraceMaker]

I few things I would initially question.

 

One - Outboards almost universally have the crankshaft angle set on a vertical axis, and I would assume the lubrication system is designed such that the engine can be trimmed to still have lubrication at a trimmed up attitude. But it may not be designed such that it can be trimmed to the attitude that a direct drive inboard sits.

 

Two - Outboard engines/bits are quite expensive. - I would be curious what maintainance costs for a Yamaha outboard - they may be super reliable. Been awhile since I've had an outboard.

 

Three - Aren't there any other sources of modern 350+ horsepower engines that would be appropriate?

 

Four - What about that whole evinrude E-Tec 2 stroke with valves and wet sump lube?

[Ryno]

There's plenty of options in you want a smaller engine that will still deliver the power. Just get a modern alloy V6 and turbo charge it! You wouldn't necessarily have to pay the premium for the yamaha or mercury engines you have outlined above, as you could use a modern car engine with a closed cooling system.

At the end of the day boat manufacturers are using big block V8's because they're cheap, simple and deliver the power. There's no question you can make a slalom boat better by stripping as much weight out of it as possible (engine included) but there's not going to be much of a market for a boat that costs just as much, but with less creature comforts.

[Dacon62]

@bracemaker - While the Evinrude 300 HP E-Tec is a viable option I left it out because it is a 90 degree V.

[Ed_Obermeier]

I concur with @ryno. IMO their are 3 primary issues in play here. 1) The price point the boat would sell at, 2) is their enough profit margin in it for a manufacturer to be worth messing with it, and 3) what level of tradeoff of creature comforts versus lighter weight would be acceptable to the target market for this particular boat. Like most things, there are a number of ways things can be done IN THEORY and make a completely workable product. Where the rubber hits the road is in sellability. If it's not price competitive considering all the tradeoffs, if it's too stripped down, if you can't make any money building and selling them likely it ain't happening.

[A_B]

dilithium crystals !

[Wish]

I think there were several low cost stripped very light waight tugs in the late 90s early 2000s that didn't sell well. Moomba Bumerang, Malibu Tantrum, SN 176, Gekko GTS come to mind. Not a lot of longevity in these models standing the test of time. The idea of sales for a stripped tug....that ship has sailed (punn intended). Outside the box thinking may prevail at some point. There's boats on the intercostal golf coast rivers that have outboards under the box midship like an inboard. They use them for blue crab fishing I believe. I think I've even seen them up on plane.

[BraceMaker]

Aztec Marine...

[BraceMaker]

Problem is this thread is really a premium boat issue. Do our boats need different engine tech? Would you pay more for a narrower hatch?

 

On the other side would you buy a small light boat with ~200 hp for 14k new?

 

 

[GAJ0004]

When I was thinking about using the powerhead from an outboard(just the engine portion at the top) I forgot to mention a different transmission to adapt it to an inboard would be needed. Not sure if the powerhead from an outboard could generate the same amount of torque as a regular V8 engine. I see a couple of advantages with an outboard powehead, and an aluminum hull. Theoretically you could have a smaller boat with the same amount of interior space. It may be possible to build and 18 foot boat that has the same interior space as a 20 foot boat we use today. The hull would need some type of frame/stringer system and a foam that would provide sound dampening, floatation, and vibration dampening. The ride may not be as smooth in rough water, and it may be harder to make the boat track properly through the jump and slalom courses. The other possibility is a rotary engine/wankel for less vibration. Not sure if they would produce enough power. It would be an interesting experiment.

 

[Wish]

My dad and I just talked about the Wankel engine this afternoon. Mr. Wankel got a patent for that thing in 1929. Developed it for production in the early 50s. They can be found in cars, motorcycles, snowmobiles, chain saws and other applications. It's physically quite a bit smaller and much lighter. Although, the Mazda Rx-8 utilized the high revving engines in the mid 2000s, they also replace the motor free of charge for yrs under warranty do to the lack of reliability. I think they have improved that though. Not great on gas mileage for that car either. Supposed to be fast and responsive. Top Gear liked it... a lot.

 

[6balls]

@wish, my RX8 went thru gas and oil like a fiend and I went through 2 engines on warranty. Very short on torque, ok on HP at high RPM. When warranty was done and my check engine light came on...I traded. Great handling car, looked cool, but I don't see a wankel in a boat (or in any future cars).

[BraceMaker]

Those wankels are fun in suped up form - modded out they rev to infinity and make crazy numbers. But in a very unuseful configuration.

 

But I think this brings up something we really do not see in boats. Transmissions, there was atleast one wakeboard boat that had a 2 speed, forget who was offering it now. But what about CVT's?

 

Why not a smaller (comparitively) turbo diesel, set up more like a generator - constant RPM @ peak power. With a CVT that would then adjust your prop RPM in relation. If you didn't need power it could cut engine RPM for efficiency.

 

I think many of the concepts that work for cars are opposite for boats - boats are more like tractors or generators than they are cars.

[Wish]

@6balls. what portion of the engine failed? Always wondered. Not that many moving parts to go bad. Accept one all important baring yes?.

[BraceMaker]

http://www.speed-industries.ch/wordpress/wp-content/uploads/2011/04/Hoon-build-17.jpg

[eleeski]

There is a lot of weight reduction possible in a ski boat. Some of it is in the engine. Weight reduction starts cheap and gets very expensive. Stock modern auto engines have undergone significant weight reduction - adapt one of these and it's cheap. Get a bit more exotic (like an outboard) and it's expensive. A Wankel? Not only do you have to adapt the engine, you have to make the engine work - incredibly expensive.

 

I'd love to see an aluminum V6 replace the heavy steel V8s. HP seems to be there. Physical size and weight is less. Hopefully, fuel burn will be less, lighter weight will make the wake better and the boat will be towable with a smaller car. Since some powerful V6s are in cars, the costs should be reasonable (are current engine prices reasonable?).

 

Mated to a light efficient boat (the 200? Just kidding. 84 American skier! with careful construction techniques) we could end up with a great ski and family boat.

 

Eric

 

 

[gregy]

There are all aluminum gm engines out that would bolt-in. Cadillac northstars and shortstars had great power to weight ratios. The flat opposed Subaru engines could be interesting.

[RichardDoane]

@wish - the apex seals (pictured by @bracemaker) were typically what would fail in the rotary engines we used to run in our RX-7's, destroying the rotor housing and putting you out of the race, but oil starvation was also a problem if you didn't go with a larger volume system

[6balls]

Yep, apex seals. They never bothered fixing, just stuck a new one in there. After two and numerous reports of others going through at least 2 motors I asked if there had been any fix or design change in the one they are sticking under the hood. Nope. Became time to move on.

[DW]

It really boils down to demand & cost. The iron small block V8 is dirt cheap, all the tooling has been paid for many moons ago and the assembly is really inexpensive (plant location) so very difficult for any other type of unit to compete. Boats, believe it or not given the price, are pretty price sensitive. There are no regulatory drivers to make them comply to economy, weight, emissions issues so there is no priority to invest $$ for those issues. Only a small handfull really care about weight, so also not a priority. So, in the end, for the manufacturers, the super cheap iron small block is the choice. BTW, the aluminum small block costs several times that of the iron one, so not a reasonable choice by the boat manufacturers.

 

The one aspect that is looming, is the long term plan to stop production of the iron small block, that will drive alternate options down the road. Mercruiser is already manufacturing a big block version of the GM unit as that is at the end of the road also.

[BraceMaker]

@6balls - I think that Toyota thought they had solved the problem when they brought the RX8 into production with the new version, different seal material. Ultimately no go on it lasting, its a tough seal, doing the same job as piston rings.

 

@DW - do you see a reason we aren't going towards a transmission instead of a more exotic engine?

[rodltg2]

How did the Toyota perform. I've read their wakeboard boats consumed a lot less

[Dacon62]

Didn't Mazda have the RX8 and wankel motor?

Toyota made some boats with a Lexus motor. Heard they were great engines.

[BraceMaker]

Ya Mazda - my mind was elsewhere.

 

 

[BraceMaker]

@Dacon62 - Engine was called a Toyota VT300i - it was the block from a Lexus 400.

 

Unknown about the lifespan of the engines, just recall the warped hull issues.

[Dacon62]

@Bracemaker - Thanks for clarifying.

What was the scoop with that engine. Was it a variable valve timing 3 liter as the name suggests?

[DW]

@Bracemaker: again, probably a cost issue. In addition, any system that puts power through a set of gears to alter the ratio incurs some power loss or efficiency loss. Direct drive mitigates that. A transmission simply attempts to more effectively match the power curve with the requirements at that point in time, so for start up a lower gear allows the engine to be in a more optimum power band to deliver the needed grunt (in a car). The transmission in a boat simply allows the manufacturer to tune the chosen prop size (diameter and pitch) to a specific point in the power curve. The chosen prop needs to be more efficient than the trans losses to come out ahead or put the engine in a more efficient spot on the power curve.

[BraceMaker]

I agree with all that of course @DW - And I've taken apart velvet drives, including the gear reduction housing.

 

And obviously as 1:1 transmissions have slipped from vogue and the norm being somewhere around 1.2x:1 - they have determined that it is more efficient to swing something bigger/steeper than a 13x13.

 

I still feel as if using the throttle to control boat speed is not really matched well to boating. We have an engine that predictably makes power at one spot, and uses the least gas at another spot. It would seem that with something similar to the metal link belt CVT's (Subaru/F1) with the input/output ratio electronically managed - that we could utilize more of a constant RPM engine set, and then vary our ratios to get to speed - and in doing so go to a smaller aluminum blocked diesel or similar, and get better $/hr to run, and still good pulls.

 

 

 

Although I am of the mindset that I would buy the cheapest boat that I knew to be useful - so this would probably cost more initially.

[A_B]

Toyota Marine sort of missed the mark with the engine. It was 300hp and 310ftlbs of torque, but at higher rpm ranges.

 

VT 300i Specifications

* Horsepower 300 hp 6,000 rpms

* Maximum torque 310 lb.-ft. 4,200 rpms

* Cylinder block & head aluminum alloy

* Weight (with/without transmission) 628 lbs./566 lbs. without fluids

* Engine layout V 90/8 cylinders

* Valve mechanism 32 valve twin DOHC, belt & gear driven

* Exhaust manifolds Stainless steel

* Displacement 4.0-liters

* Power to weight ratio 0.53 lbs. per horsepower

 

It also had some oddities, like changing the impeller required partial disassembly of the engine (so I heard).

 

I think the molds were left out in the sun and they developed a hook or something, that made them unstable.. so the story goes..

 

 

[usaski1]

What happened to the Toyota boats? Obviously they did not catch on, did they have a slalom tug? Was it any good (wake?)

[jcahlmn77]

Has anyone thought of turbocharged V6 engines? I know turbo/superchargers have always had reliability issues, but in the case of FORD, their ECOBOOST V6 engine has been proven to be extremely reliable over millions of miles of pre-production road testing. Fords website says "EcoBoost engine underwent over 1,900 hours of testing at full-boost conditions, as well as thermal testing to simulate 10 years of operation in the harshest environments". This engine would be an awesome candidate for a V6 ski boat because of its excellent reliability, great fuel economy, small size, light weight, and high power (365 hp and 420 lb ft. of torque, all available at only 1,500 RPM).

[Ed_Obermeier]

Reliability in Ford's ecoboost engines remains to be proven IMO. Ford's record with turbos to date, particularly in their diesel engines, is spotty at best. With anything marine you want fail-safe-as-possible reliability. Torque in a small turbo equiped engine comes on at higher rpms, not exactly ideal for a marine application where you want low end grunt. I'll pass, thank you.

[GAJ0004]

I was talking to a marine mechanic a while back, he said many engines would work in inboards, but most are not cost effective to marinize..

[dbski]

I have a Focus ST with the 2.0 ecoboost. I've owned other turbos before and yes there was turbo lag. The ecoboost is a lot different, it develops its full torque by 2500 rpm. Comparing it to the Audi A4 I had prior is night and day. The ST pulls hard at low rpms. Although I doubt it will ever happen, I bet the 3.5 would make a great boat engine. Off subject, if anyone is looking for a great small car go test drive a ST.

 

[bogboy]

Which is why I thought the proven marinized g.m. 4.3, or g.m 3.0 in a direct drive, matched to new smaller light weight methods, while still keeping creature comforts might work. Or is it an answer to a problem that nobody asked?

[BraceMaker]

@usaski1 - History of Toyota boats is pretty much.

 

Talk comes out mid 90's, Late 90's think around 98 the first boats are in private owners hands.

 

Fairly small dealer network - with limited amount of product on hand - tough sell.

 

Then comes the warped mold, and a number of tweaked hulls going out, which of course the dealerships that were selling the boats had complaining customers, and in turn complained to toyota, who eventually recalled/replaced all the boats made out of that mold. And that brings you right up to the end of the line in 2001 - so I would imagine a pretty fair engineering/design cost to bring the product to market, new hull, new engine/drivetrain, and at a 500/yr production, from the late 90's till 2001, I bet there are fewer than 2000 boats made.

[Dacon62]

From the limited info I have I think most of the smaller engines posing in place of larger displacement offerings are usually supercharged instead of turbocharged. No lag, fewer bearing issues as you are working on the cooler intake side as opposed to the hot exhaust side.

Over the years engine hp has gone up from the bullet proof PCM 351 - 240 hp to todays 340-350 hp and at the upper end 400+hp engines. Even considering that the old boats weighed about 2,250 and todays tugs are at 2,850 the weight/hp ratio in todays boats is, as expected, better. Leaving the drag of a larger wetted surface out of the equation for now the old 240 hp had to push 9.4 pounds for every 1 hp were the 350 hp only has to push 8.1 pounds. Todays elite athletes are doing better partly because of newer technology. Stronger pull, straighter tracking, carbon fiber, etc.

While I am all for a smaller fuel efficient motor to power todays boats. I don't think I would vote with my wallet to pick a boat that would be slower out of the hole and give up some of that solid pull todays thundering V8's give us. The only way thats going to happen is if that supercharged 6 pulls as hard or harder, has better fuel economy, frees up a bit more interior space and gives me an ever so slightly smaller, softer wake before it gets the nod. Check, check, check...and check.

[DW]

Marinizing a turbo unit will add additional cost to the package, you will need to add cooling since the engine box will tend to be a close fit, turbo's generate additional heat which is trapped under the lid, so some R&D and validation will be required. The power curve of a blown smaller displacement engine is not ideal for a DD ski boat (unfortunately). Biggest challenge would be the off idle pull up power needed. There will be newer stuff tried as the iron small block dissapears over time. . .it will add to the cost which is the biggest challenge for the manufacturers.

[estrom]

The solution seems simple to me - give it a little burst of NOS off idle to assist holeshot! (And have your skier sign a waiver absolving you from any shoulder injuries!)

[rok]

@Ed Obermeier hit the mark - skiboat engines need torque down low, which brings to mind the old hot rod axiom, "there's no replacement for displacement"... You can turbocharge an engine, but it will typically make power at higher rpms only. Supercharging (pulley or gear-driven forced induction) will help a smaller displacement engine make big power in the low-rpm range, but with added expense and complication, I don't see it as a viable substitute for a big-cube V8. Wankels and two-strokes are characteristically high-rpm power, lower torque engines as well. You can re-engineer them to bring on the power lower in the range, but it's against the nature of their design - I guess that's why we still see 99% of our slalom boats driven by big V8s.

Refining the current V8 engines' management systems, as well as better combustion chamber design are the short-term future for better economy & power (where we need it, i.e., in the low rpm range), IMO. Turbodiesel power seems like a possible alternative too, if the cost of diesel oil becomes significantly cheaper (and cleaning up their emissions too).

Another aspect is the weight. Sure, lighter is better, but up to a point: slalom boats benefit from the inertia to keep the pull constant.

Great post!

[sixball]

The Ford Ecoboost reaches 90% of its peak torque down at 1,700 RPM. Something like 430Lb-FT

It holds over 400 Lb-FT out past 4,000 RPM. I don't think it would be a big fuel saver pulling big torque numbers all the time. It cools the turbos even after key off witch is the cause of many turbo failures. It may be a good choice!

 

 

[XR6Hurricane]

I would think today's direct-injected two strokes could probably be installed horizontal without much of an issue, though I'm not sure if it might affect the oil routing through the rods and mains, which is where it first travels before getting re-routed back into the fuel mixture. The D.I. 2-strokes are also horribly expensive to repair and are much more temperamental and fragile than what outboards used to be. A four stroke outboard would probably need the oil reservoir and pickup reworked.

 

I'm an outboard fanatic and there's a good reason why I grabbed one final carbureted 2-stroke Merc 150 in 2005 before they pulled the plug.