G21 motor

[vanhanbr]

Let me clarify some things,:

According to the 2014 owners manual the maximum cruise speed for the 343/409/450 is 4000 rpm. That is different from cruise speed, which is typically the term used to describe the most fuel efficient speed to travel to get from point a to b.

I used 14 pitch as an example because more than one poster mentioned propping down to improve pull times. I agree that it takes real world testing to find actual speed, but you can not go any faster than the calculated theoretical speed (0% slip). Slower, yes, I used 10% slip because that is pretty much best case real world and what I experienced on my own boats as well, 0% will never happen.

The 343 might be ok for surfing, but what if I just wanted to go for a boat ride? or drive to a surf spot? 19 pitch prop, max cruise speed 32mph or you can still cruise at 24 mph and 3000 rpms. I think it is safe to say the 343 will not spin a 19" prop.

Tallredrider 30 mph with 17 pitch prop 2.00 tranny 4000 rpm is 7% slip, 29mph is 10% slip What you said sounds about right.

Straight from owner's manual :

Best all-around performance and maximum engine life is achieved when the engine is propped to run near the top of (but within) the recommended full throttle RPM range with a normal load.

The potential buyer should load the boat up at whatever elevation, crew, ballast, etc. is "normal" and make sure the 343 can still spin to 5000 RPM WOT (per manual.) Then we would know if engine damage could occur.

[Sailfun]

[QUOTE=xrichard;n538039]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.

The above would only be correct if the prop slipped to the point the engine was on the RPM limiter. Back in the days when waterski magazine actually did real boat tests they did acceleration tests with boats dragging a sled. The results were interesting. I also owned the exact same hull design with two different motors. Next time you are out on your boat have someone video the boats speed and RPM as you accelerate. You want peak torque at the RPM the engine is spinning the prop as the boat cones out of the hole. RPM comes down on most boats because the throttle is pulled back not because the prop hooks up.
The other thing to keep in mind is where peak torque occurs is one data point. You need to look at the entire curve. Often the engine with the higher peak still makes more torque from 3000 on up.

[xrichard]

@sailfun....could be that where the motor is spinning relative to the RPM limiter is key, but it's not making sense to me given the prop has no idea where the rpm limit is. It's just spinning without reference to how fast the motor can potentially spin. I think the bottom line of what you're asserting is that more revolutions even with huge slip equals more acceleration? It's true: some additional torque will be usable even with massive slip (which is why I pointed out the analogy to cars is not perfect), but likely not much. If there's a link with actual evidence otherwise, that'd be great.

I'm interested in your experience with the same hull and two different engines. Was everything else the same (e.g. prop and tranny), you experienced similar slip on both (meaning similar rpms during acceleration) and you found the one with the larger engine to accelerate faster? Was the only difference in the RPMs (e.g. slip) and you experienced more acceleration? Did you measure it or was it seat of the pants? I wasn't sure from what you wrote. The same concerns for waterski magazine tests....it could be they show a larger motor accelerates faster, but I doubt that would be a larger motor by itself. Perhaps....if even more slip adds a meaningful amount to accelerations. Typically, it would be because the larger motor can spin a larger diameter prop (or one with more pitch). Perhaps not, though...I haven't seen their test data.

I also wasn't sure what you were getting at re: throttling back. Of course rpm comes down because we pull the throttle back to maintain the speed we wish. Otherwise the boat would continue accelerating until the torque generated does not exceed the torque required to move the boat through the water. Which is why the 343 might have a lower top speed than the 409 given the 409's torque curve is higher than the 343 past about 3500 rpm (though I don't know if that's true at max RPMs). It's also the reason why I expect the 343 to accelerate more slowly than the 409 above +/-20-25 mph. (BTW, I haven't looked back, but my recollection is that the 343 outperforms the 409 wrt torque below 3500 rpm.)

I don't have a dog in this fight, 343 vs. 409. However, first hand accounts are that the 343 does everything you want it to do in the typical application for the G21....surfing, wakeboarding, cruising, top speed. The only reason I got involved in this discussion is because I see quite a bit of FUD surrounding the 343 and the G series and I think it's unfortunate.

[Sailfun]

Basically it comes down to you need Torque in the operating rpm range the engine is at while accelerating. Given the exact same slip be it 10 or 50% with more torque you can spin a more aggressive prop and will get better acceleration. My 2001 VLX had a base motor with the torque curve lower in the RPM range. The 2002 had a hammerhead with less torque at 3000 but a lot more at 4500. Same prop and tranny. We could carry more weight and accelerate quicker with the hammerhead.

[vanhanbr]

I think the point I was trying to make is that you can't take the same engine that was in the OG210 / 196s and toss it into a new boat 2000 lbs heavier and expect the same level of handling, acceleration, top end speed, etc. A few people chimed in saying the 343 worked for them (mostly surfing) and that's great. The engine may be overworked to to point of early failure, we're not sure, but that really isn't the point either.

I was just asking why? I wouldn't buy a corvette and then "cheap out" and get a V6.

If money is the issue, buy a 230. It is cheaper, lighter, will handle better, has better acceleration, top end speed, comparable room, and probably has a better surf wave.

[xrichard]

Basically it comes down to you need Torque in the operating rpm range the engine is at while accelerating. Given the exact same slip be it 10 or 50% with more torque you can spin a more aggressive prop and will get better acceleration. My 2001 VLX had a base motor with the torque curve lower in the RPM range. The 2002 had a hammerhead with less torque at 3000 but a lot more at 4500. Same prop and tranny. We could carry more weight and accelerate quicker with the hammerhead.

No argument that more torque lets you move a more aggressive prop. If propped accordingly, a more powerful engine will deliver more power to the water.

But the whole issue here is the 2014 G21 came with a 17x17 and both the 343 and 409 appear to be adequate in both surfing and wakeboarding applications....as well as cruising and likely top end. The OP was concerned for his friend re: the 343. The evidence is there isn't really a concern...except wrt resale value.

[vanhanbr]

But the whole issue here is the 2014 G21 came with a 17x17 and both the 343 and 409 appear to be adequate in both surfing and wakeboarding applications....as well as cruising and likely top end. The OP was concerned for his friend re: the 343. The evidence is there isn't really a concern...except wrt resale value.

What evidence? No one has come on this forum with a loaded up G21/343 combo and stated their RPMs at WOT. It needs to hit 5000 RPM or the engine is being pushed too hard. Blowing an engine is a pretty big concern.

The "evidence" thus far:

mlsurf said he had no problems surfing only (didn't mention wakeboarding, etc) and showed a pic where he didn't fill the factory ballast completely and only had 2 people in the boat. He didn't mention elevation.

scottb7 said he knew of others that had luck, didn't mention specific names. He also said you could prop down if need be.

Unless I missed something, no one said the 343 with 17" prop would be a wonderful do everything boat, in fact, the opposite was posted:

The OP mentioned the seller stated right off the bat that the boat struggled at wakeboarding speeds.

Others in the 550/ 2.0 tranny prop thread that you reference mention either wanting to prop up because they hate running the high rpms of the 17" prop, or mention that they don't think their bigger (h6, etc) engines have enough snot to pull anything bigger than the 17" prop.

[xrichard]

Evidence of no problems from people with first hand experience: mlsurfco says surfs fine with large crew and extra ballast. Jeff (edited...I originally wrote Dave...sorry about that) says G21/343 wakeboards w/o problem with short setup and full load of media in the boat. Are they lying?

I think those two data points are meaningful especially when combined with the known facts re: the torque curve vs. the 409.

What you're calling evidence, 1. the seller referenced in the OP is a dealer who likely has no first hand experience (in my experience, most dealers are clueless wrt how these things are actually used)...and might have the "343 isn't enough" bit running through his head. Who knows....might be good evidence? 2. The reference to the thread on the 550 prop selection was entirely to point out that a person with a 409 moved to a 3047 and did not see performance declines. Not sure the value of untested personal opinions are re: the H6 and the 3047. (FWIW, my guess is the H6/3047 would be a great combination) 3. Scottb's comment was simply what we know about motors/props: if it needs more umph, you can always prop down. He didn't say it needed more umph and also didn't say he had experience with it. He said his views on it are his personal opinion and he thinks it might not be adequate.

I'm also not sure why some have their panties in a wad over this. My recommendation is try it out...but don't prejudge just because you have a bias toward a bigger engine. The assertion that the 343 is inadequate and the 409 is adequate in most stock G21 applications doesn't make sense on the face of it. Plus the few first hand experience we've seen say the 343 is not a problem. I haven't searched in other threads....maybe there are more first hand experiences out there?

So...believe as you wish. If you think the 343 won't cut it with full ballast at lower elevations, then don't buy one. But the recommendation to others should be to try it out and be aware of resale issues because there is a bias against the 343.

[vanhanbr]

But the recommendation to others should be to try it out and be aware of resale issues because there is a bias against the 343.

I guess we're going to have to disagree on this one.

[DocPhil]

the 2:1 v-drive was not available in 2014 my.

wrong

[DocPhil]

Ok so I actually went out on the boat and I can say the following with 100% certainty.

I HAVE ZERO CONCERNS ABOUT THAT MOTOR IN A G21

It performed amazingly well. I even had the dealer take a video of the boat coming up to speed fully ballasted wakeboarding and it took about 7-8 seconds to reach 23.6 mph. I will have him post it up on youtube and I will link it here.


CRUISING-the boat comfortably cruised at about 28-30 mph around 3800 RPM. I have no problem with that


SURFING-fully ballasted it got up to surf speed in about 4 seconds and surfed 11.3 mph at 3000 RPM


WAKEBOARDING-As stated above it planed out and got up to 23.6 mph in about 7-8 seconds with zero issues at all


For those of you that have been talking so much trash here without ever being in that boat with that motor, you need to experience it. The motor does just fine and has more than enough power. Another thing that I noticed was that it was super quiet. Much more quiet than my H6 in the G23.

[Evening Shade]

Ok so I actually went out on the boat and I can say the following with 100% certainty.

I HAVE ZERO CONCERNS ABOUT THAT MOTOR IN A G21

It performed amazingly well. I even had the dealer take a video of the boat coming up to speed fully ballasted wakeboarding and it took about 7-8 seconds to reach 23.6 mph. I will have him post it up on youtube and I will link it here.


CRUISING-the boat comfortably cruised at about 28-30 mph around 3800 RPM. I have no problem with that


SURFING-fully ballasted it got up to surf speed in about 4 seconds and surfed 11.3 mph at 3000 RPM


WAKEBOARDING-As stated above it planed out and got up to 23.6 mph in about 7-8 seconds with zero issues at all


For those of you that have been talking so much trash here without ever being in that boat with that motor, you need to experience it. The motor does just fine and has more than enough power. Another thing that I noticed was that it was super quiet. Much more quiet than my H6 in the G23.

That's awesome. I didn't expect that. That old school 350 still getting it done. Pretty cool.

I wonder what makes it quieter than the LS based GM engines?

[DocPhil]

That's awesome. I didn't expect that. That old school 350 still getting it done. Pretty cool.

I wonder what makes it quieter than the LS based GM engines?

Direct injection is louder isn't it?

[xrichard]

@DocPhil....I'm glad you tried it out. That's +/- the same performance as a 409 in a G23. I run about 8-9 seconds to 23.5 and cruise at 3500 rpm / 25mph (...at least I'm pretty sure of the cruising bit...I can double check today). Stock 17" prop and 450' elevation.

BTW, when you mentioned video, it reminded that there was a video posted by a dealer back in 2014 showing a 343 and 409 accelerating side by side with full ballast. The 343 pulled slightly ahead of the 409 by 23 mph.

There is still the resale issue, so the price has to be right....you've seen the bias here.

Out of curiosity, what's your elevation?

[DocPhil]

@DocPhil....I'm glad you tried it out. That's +/- the same performance as a 409 in a G23. I run about 8-9 seconds to 23.5 and cruise at 3500 rpm / 25mph (...at least I'm pretty sure of the cruising bit...I can double check today). Stock 17" prop and 450' elevation.

BTW, when you mentioned video, it reminded that there was a video posted by a dealer back in 2014 showing a 343 and 409 accelerating side by side with full ballast. The 343 pulled slightly ahead of the 409 by 23 mph.

There is still the resale issue, so the price has to be right....you've seen the bias here.

Out of curiosity, what's your elevation?

Yeah, it's amazing the misinformation out there. Mostly perpetuated by people that have never experienced these boats it seems.

We are at about 750 feet elevation.

I have no doubt that elevation would play a role and who knows? The performance may be completely different at high elevations. However, for most people I think the 343 in the G21 and as you stated the 409 in the G23 would do just fine.