Was watching Ship Shape TV....

[BQUICK]

...maybe that was my first mistake...
Anyway they were talking props and said vent holes were used in for 2 strokes due to their lack of torque planing off. Ha? I think 2 strokes have better holeshot. The 4 stroke powerband is higher....not much happening until 4000. Drove a 28ft boat with twin 150 Suzuki 4 strokes and you practically had to nail it to plane off and if rpms went under 3800 it would fall off plane.

[pstephens46]

Somebody is trying to start trouble!

[boscoe99]

Quite true that the Vmax propellers for the two stroke Vmax models use vent holes whereas the Vmax propellers for the four stroke Vmax models do not. To help the motor be able to spin up to speed.

In the olden days two strokes had relatively low bottom end torque.They had to wind up to create power. They were also really really fuel inefficient. Much has changed.

In my life I had a Mercury 175 EFI motor (two stroke) and a Yamaha F200 (four stroke). Maybe it was the added 25 HP but I could not detect a dimes worth of difference in engine power between the two. However, the qualities of the four stroke were so superior to the two stroke that is was damn near unbelievable.

I fail to see the need for whatever added torque a two stroke may offer. Maybe some need it.

The only indisputable fact, which drives two stroke advocates crazy, is that four strokes are much, much more desired than two strokes. Why? Only the buyers know for sure.

But I do agree that watching ShipShape TV is a general waste of time. I might as well be watching the show where the guy hawks the vegematic machine.

[JerEazy2]

unrelated video - but interesting none the less.

http://www.boattest.com/engine-revie...-4-Stroke_2018

But I have been told the 4-stroke power band has to do with the generally larger props that 4-strokes tend to use. So the hole shot isn't as nice, but it makes up for it on the top end? My experience with the 4's is the same as you, less lower end, not as nice of a hole shot. But, i have only ever owned 2-strokes. So i might be biased.

[BQUICK]

Not sure what that video proves except that in that situation the 4 stroke is a dog. A better test might be two identical boats drag race (time to plane, top speed) them then load them down and see how they react. Based on that video I bet a four stroke powered boat loaded down is still going to be a dog.
Another thing is that is you look at boat tests the 4 strokes have to rev to 6000 for top speed but the 2 strokes 5500.....and the 2 strokes can run there for extended periods. I doubt many 4 strokers are running 6000 for more than a short time.. Plus they start to get as loud or louder than 2 strokes over 5500. Not trying to start trouble.Just discussion.......
I'm sure people who dumped tens of thousands of dollars into getting 4 strokes are going to defend them. Human nature. Similar to some people who buy new cars....

[pstephens46]

You'll probably find many more people that give a sht over at THT. Always a thread on this topic over there. Say hello to Whaler27 for us.

[zenoahphobic]

I don't think the video did a fair test.

It was demonstrating a dual engine setup boat performing on one engine. Therefore in single engine mode the props used were not pitched for WOT max revolutions, and I don't understand why no attempt was made to do this. Clearly the Yamaha performed like a dog, so why did he say the 18" prop was the lowest he could go for safety?

The test should have at least tried a prop on the Yamaha that brought the boat up onto the plane, as at that threshold a few ponies can make that significant difference.

I suppose there is a limit to any test. But a dual 200 Yamaha setup comparison with a dual 150 Evinrude setup would have been far more
usefull.

It does however make me worry about the lack of low down grunt of 4st Yamahas though, to the point that I am concerned if I replace my 175 v6 two stroke Yamaha with a 4st Yamaha, that a 225 (the max I can go) may still be disappointing in the hole shot department.

[TownsendsFJR1300]

I re-powered from my V6 Evinrude 150 to the F150 back in 2006.

The rude was about 10 years old and starting to give me issues. (carbs, fuel issues-wish I knew about RF and Gas Shok back then)

The F150 was improperly propped (big time), trim tab set incorrectly and would barely get on plane.

Once re-propped CORRECTLY, the Yamaha MIGHT BE a second slower on the hole shot compared to the Rude), a knats hair slower on the top end but the mileage is EASILY 3 times that of the rude... An entire days outing, on and off with the engine, NOT 5 gallons...

I don't like the extra weight, more maintenance on the Yammy but it's 12 years old and short of some fixes (balancer, starter relay, T&T relay), it's not broken in yet, and I trust it. It'll be the last engine I purchase for my lifetime.


Just had it out today, in rough water, ran like a champ (not run since Hurricane Irma((9-2007))-out in the river). Short of my T&T relay sticking up (and got replaced once home today)

I love the two stroke and wish I would have purchased another but the performance of my F150, I can't complain about at all.

[zenoahphobic]

I know this 2 versus 4 stuff debated a lot. My experience pretty much 2stroke, sat in a boat with 200 4st Yammy once or twice but these were largely tourist boats, Thailand Fiji etc and I wasn't impressed.

I wonder if there is a parallel evolution as there was with motorcycles. Cubic capacity was the comparison not actual HP between motorcycles, and of course two strokes won hands down for a couple of decades. Weight, like with outboards, was a significant factor in performance (power to weight ratio).

However, unlike outboard motors, 2st did not run parallel with 4st as much. Overnight 4st replaced 2st on the road. And gov legislation drove harder for motorcycle change than it did for outboards. Motorcycles today are powerful, light and fast.. fast, and have low end grunt.

It has often been concluded that outboard development is lagging behind cars and most certainly motorcycles. And I wonder that some more evolution has to happen, before it truely will be accepted, that 4st will be better than 2st, as it seems to be without a doubt in the M/C world.

BTW I have had no trouble from my 17 year old 175 two stroke saltwater Yammy (slight leak on tilt ram only, no need to hurry to fix). And maintenance, what maintenance? Bit of oil, grease, plugs every ten years, impeller now and then, carb clean once.....and it still fires instantly. When warm a blip of the key, the starter you can't even hear before engine idl es.

Minimal maintenance requirement, reliability, long life, and grunt are the hallmarks of Yammy two strokes. The four strokes is fuel economy and quietness (below full power).

[rodbolt17]

the 200 2.8 l 4 stroke will smoke any 200 two stroke smoker.
when Yamaha started playing with VCT, it made the 4 strokes wake up.
yes the vent holes allowed enough ex gas to vent the prop allowing the engine to spool up quicker.
typically only flats and bass boat type rigs used them. most tech still have no clue.

[Keith Ohanesian]

So how would a vented prop work on a 4 stroke? If their power band is higher up than a 2 stroke I feel it would be like putting a looser converter in my drag car.

[walleye1]

Mercury built there bravo 1 fs for there verrado. that is what i run on my 225 opti pop.

[walleye1]

I had a 2011 2100 skeeter with a f300 that got shiped with a 21p 3 blade turbo prop, what a dog. I put a 23p bravo fs on it with all the plugs out
and gained on top end and hole shot.

[rodbolt17]

what you do not understand is when that leg is buried the air pump(powerhead) has to overcome a lot of ex gas back pressure when the throttle is opened rapidly.
almost all the ex gas then has to shove the warter out of the ex tube and out the prop at a slow hull speed. eats up time.
the vents simply allow ex gas to ventilate the prop blades allowing the prop to spin up faster cause it is "cavitating" although it is VENTILATING.
I mentioned cavitating cause you may understand that concept better.
once up at planning speed it is a tad different.
think about it.
the gearcase leading edge and body displace water.
this can create a vacuum behind the case as the water has to move back.
that is the whole reason for through the hub exhaust. without that vacuum the case moves more efficiently through the water.
this stuff aint rocket science. in fact it is about 8th grade earth science.
and that is why most auto or diesel techs suck at outboard and stern drive work. a drag car may have to use max HP/Torque for maybe 12.5 seconds or less.
go to any auto shop and tell them it only acts up after 45 min at 5900 RPM.
the marine engine duty cycle is somewhat different than automobile.

[oldmako69]

Coriolis effect is greater on 4 strokes.