G21 motor

[vanhanbr]

What is the point of owning a slow moving turd of a boat that's propped to top out at around 20 mph? Hope he doesn't have to travel far to get to a good surf spot. Need to save some money? Just buy a 230 then (and not one with a 343), it will be cheaper and probably have a better surf wave. LOL

[vanhanbr]

Top speed can be calculated. Say you prop down to a 17x14 prop, at 3800 rpms, max speed is 23 mph at 10% prop slip.

[GMLIII]

What is the point of owning a slow moving turd of a boat that's propped to top out at around 20 mph? Hope he doesn't have to travel far to get to a good surf spot. Need to save some money? Just buy a 230 then (and not one with a 343), it will be cheaper and probably have a better surf wave. LOL

Took the words out of my mouth, LOL

[OKWAKEBDR]

Right but the G also has a 2:1 tranny and 17 inch prop.

The 2:1 V-Drive was not available in 2014 MY.

[Tallredrider]

Top speed can be calculated. Say you prop down to a 17x14 prop, at 3800 rpms, max speed is 23 mph at 10% prop slip.

Max RPM is around 5200 RPM...so it seems strange to say Max speed is 23 MPH. The slip must be highly variable because my G23 with 17 X 17 surfs at 3800 RPM if I have a lot of people on board.

The tranny ratio needs to be verified as well, here. I was also thinking it didn't come until 15.

[vanhanbr]

Prop slip is highly variable, 10% is pretty much best case scenario. Max rpms may be 5200, but max continuous is 3800 (maybe 4000.)

[Wayward]

The 2:1 V-Drive was not available in 2014 MY.

My 2014 G21 definitely had a 2:1..... and a 17x17.

[Laptom]

2:1 was available in 2014 for the non charged engines.

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[scottb7]

Jeez...Lot's of people are having success with 343 on a g21...So if you re-prop you will be fine to pick up some more power and lower top speed a little bit....If you re-prop to 17.0 x 15.5 or 17.0 x 14.0 you are not going to lose much top speed. Rpms may go up a bit.

I think people are putting 17.5 and 18.0 diameters on g23, so maybe can put one on g21. I don't know if they fit, easy to measure.

I do agree that there will be a large re-sale issue. So basically it is a pay now or pay later.

[xrichard]

I wouldn't reprop until trying it out. In fact, we've had a thread going here discussing putting larger-pitch / diameter props on Gs with 550s in order to de-prop it. Wayward said his buddy with a G23/409 combo used a 3047 and didn't notice a difference except in lower rpms and less fuel consumption. That bodes well for a G21 with the 343 stock setup.

In any event, a couple of things about some of the comments above.

First, the 2014 had the 2:1 transmission as others have noted.

Second, the assertion that the motor spins above 3500 rpm coming out of the hole and, therefore, takes advantage of stronger torque at those rpms (e.g. 343 vs 409) isn't actually true though it sounds correct. The reason is prop slip. The prop is slipping +/- 50% when the boat is moving toward wakeboarding speed. That means much of the torque of the motor, even if it's spinning 4500 rpm, is lost to slip. You can compare it to a car: if you lose traction (e.g. spin your tires) accelerating full throttle to 60 mph, the motor that can spin your tires faster doesn't get you to 60 mph any more quickly. Once you lose traction, the excess torque is no longer transmitted to the ground in the form of forward motion (...of course, if you can modulate on the edge of traction, a stronger motor will perform a bit better. But that doesn't apply here as we're not modulating throttle on our way to 23 mph) EDIT: this analogy isn't perfect, but the idea holds: if you're slipping massively, more torque doesn't help acceleration.

Third, the discussion about top speed was oddly irrelevant. Top out at 20 mph?....that completely ignores everything others have written wrt actual performance of the 343.

From what I've experienced, and what first hand accounts are telling us, is that the 343 performs well in most typical applications for this boat. There is probably an issue wrt higher elevations and perhaps very heavy loads, but I haven't seen anything that addresses how high or heavy you have to be before a bigger motor matters. I could notice my 343 struggling at a 1200' lake....but, frankly, don't know if a 409 would be any different in the same boat.

When I was looking at G21s, I decided I'd go with the 409 not because of performance but because of the unsubstantiated bias most people have against the smaller motor. I was afraid it would affect resale and decided it was one of the very few times one would get a return on a motor-upgrade premium. I never moved forward with that decision because I bought a G23.

[OKWAKEBDR]

My 2014 G21 definitely had a 2:1..... and a 17x17.

I stand corrected. Sorry about that.

[vanhanbr]

Maybe some of us just have different expectations.

When I bought my 210, I wanted it to be as "fast" (term used loosely) as my older Sport Nautique even though it weighed 1000 lbs more. So I upgraded from a GT40 to a ZR6 and I still lost a little overall performance. If I buy a G21/G23 in the future and want one as "fast," it would need a bigger engine to make up for the 1000+ lbs difference in weight.

I think top speed is in fact very relevant. A 14 pitch prop will not go faster than 24mph at 4000 rpm. If anyone tells you they are going faster, they are either lying or running the motor at a higher rpm than PCM rates the engine for. A 19 pitch prop at 24 mph is only running at 3000 rpm (10% slip.) The resale should be poor on a 343 powered G, the engine is going to be run at max rpms its entire (short) life.

[mlsurfco]

That is awesome to hear from someone with actual experience with the motor. Do you know what your RPMs were at surf and wakeboarding speeds and what you topped out at? Also what was your surf setup?

From memory, the RMPs were just under 3k. But I could be wrong.

Everything else though, we didn't put any weight up front.

• Year: 2015
• Model: G21
• External Ballast: 200 Lead in back left corner
• Internal Ballast: 2850 available but only putting weight in the back corners
• People's weight in boat during picture: Driver at 205 and passenger at 140
• Surf Settings: NCRS - 0, NSS - 0

Picture here - https://wakesurfnation.com/boat_setu...-nautique-g21/

[xrichard]

@Vanhanbr...I agree, top speed is definitely relevant as is cruising speed (which I think is what you might actually be referencing because you just mentioned 4000 rpm...?) When I said "oddly irrelevant" above, that was directed at the odd example of a "turd of a boat that's propped to top out at around 20 mph." (And the follow on post referencing top speed of 23 mph). The implication of that statement is that to be a good wakeboarding or surfing motor, a 343 needs to be propped down such that its top end is 20-23 mph. Which is counter to real world experience and might lead people to false conclusions wrt a G21/343.

What's relevant is that the OP asked about a 2014 G21....which is not running a 14" prop with a 2:1 transmission (the assumption used in your calculation above). The fact is the cruising and top speeds on a G21 with a 343 will be the same as with the 409 if they're turning the same prop through the same transmission. WRT top speed, both would have to achieve the same max rpm to achieve the same max speed. I don't know if the 343 can--I've never looked into it. Perhaps the 343 has a slightly lower top speed given it produces less torque at high rpms.

From what I've seen thus far, the only reason not to get a 343 in a G21 is resale value or (maybe) if you plan to run at elevation. In terms of resale, it simply means you have to take that into consideration in terms of how much you're willing to pay for the boat.

[Tallredrider]

Random thoughts:

I think that calculating speed is far more complicated than plugging in some RPM, pitch, slip and a tranny ratio. It depends a lot on the hull shape, NCRS, cup on the prop, etc. The slip is a total guess and needs real world experience to see where it is at. I am a science/math geek as much as anyone, but I think this stuff has a ways to go before it computes in the real world.

14/17 = 82% So everything else being equal (see comment above) a 14 pitch prop would cruise at 82% of the speed that the 17 pitch prop would. If I cruise at 30 in my G with the 17 inch prop (which I do), then I could cruise at 24.7 with the 14 pitch prop.

Guys who have actually had this boat/motor combo say it did fine for them, and didn't complain they couldn't cruise fast enough unballasted.

The torque curves are very close for the 343 and 409, and although they separate at higher RPM's it still isn't night and day difference. So shouldn't the question be 343 vs. 450 anyway?

I am not convinced that these motors are going to die an early death if you run them at 4000 RPM regularly anyway. There is a reason for the very short oil change intervals compared to your car. Break in suggests going 5200 RPM right out of the box for short intervals.