G2 vs Optimax

[powerabout]

300ftlbs at the prop from an engine that makes 300hp is way too low unless it had a speedmaster on it
300 x 5252/6000 = 262 which means at the powerhead
any reduction will increase that number
2:1 will make 262 x 2
therefore G2 could make 600@the prop especially at a lower rpm
300hp @ 5252 = 300 ftlbs
x gearbox ratio
1.85 x 300
=555

[baja200merk]

Makes sense to me and that's what I gathered but I'm not gonna be the one to contest bushs dyno sheet. Going from 3.3 to 3.4 is worth ~30ft lb. 3.0-3.4 extra displacement alone will be worth a bunch.

[Turborr]

300ftlbs at the prop from an engine that makes 300hp is way too low unless it had a speedmaster on it
300 x 5252/6000 = 262 which means at the powerhead
any reduction will increase that number
2:1 will make 262 x 2
therefore G2 could make 600@the prop especially at a lower rpm
300hp @ 5252 = 300 ftlbs
x gearbox ratio
1.85 x 300
=555

Different lower unit ratio's are not going to increase or decrease the hp of the engine. No way a g2 makes 600 ft lb of torque.

[powerabout]

read the post crikey..
BRP are saying its at the prop, nobody is talking powerhead

[racer]

Like my dyno Dave can plug in the gear ratio and the computer will give readings without the ratio multiplier.

[seahorse]

Remember that this is propshaft torque, that the ICOMIA 28-83 standards were followed on calibrated eddy-current dynamometers,and that it is engine not propshaft rpm in the graph.

[baja200merk]

The land and sea dyno we used let you set gear ratio and use the weather station prop shaft torque never got near 600 even on 450+hp 3.3s.

[racer]

I could get a modified 3.0 to make 340 plus pounds of torque if you multiply times the 1.86 ratio it gives you well over the 600 number.

Just remember another engine, Lances injected 3.3 which made 421 at what I remember 7200 which is 307 torque with peak at 5800, engine was over 300 from 5k to over 7200. If you use the 307 times 1.86 you get 571 with peak numbers much higher. What I am saying is when is says op shaft numbers are used the factories are using gear ratio

[baja200merk]

So if you made a pull and type 1:1 in the land and sea software you'd get the torque after the gear correct?

[seahorse]

Keep in mind that the Land n sea dyno is basically a load comparison device and not an accurate or calibrated dyno used by engine manufacturers or the EPA.

The hydraulic International Dyno is the same type of load device, not accurate for determining actual power or torque but close enough for determining a power curve shape and peak torque output rpm.

[ar300johnson]

I believe that that the new E-Tec makes more low end torque than a Optimax. My 250 Ho had a little more low end torque than my 300XS. Above 4000 RPM the Mercury was a lot stronger and was at least 5 mph faster. I regularly get 4 mpg from 30- 55 mph with the 300XS. The 250HO would barely get 3 mpg from 30-45 mpg. The E-Tec was a good motor. The 300 XS is better. The new E-Tec may be a much better than the G-1, but it has a long way to go equal my 2016 300XS. I hope that the E-Tec is a good motor because they will be the only 2 stroke left before long.

[blackeye]

One thing I haven't seen discussed is weight... I recently installed a G2 250 HO on my 24 Superboat. Having switched from a 99 Promax I'm figuring that I've gained about 50 lbs in the back based on her attitude when sitting and when running. I was hoping the weight would be about the same since I was eliminating the remote trim pump and reservoir, oil tank, manual jack plate and steering ram with linkage. But after I was all rigged up and launched she is sitting almost 2 inches lower in the stern. On a boat like mine which weighs about 2000 lbs., it isn't a small difference. I've added 25 lbs to the bow and and 25 lbs on the port side in the cabin (which offsets my weight on the starboard side a bit). With that change the boat has a more normal attitude when running and at rest.

As far as performance goes, I never had the Promax propped right so she was never in the sweet spot. I have gained a few mph on the top end but the most dramatic improvement is in fuel and oil consumption. I average about 4 mpg now which is about double the economy and I think my oil consumption has dropped by even more. One thing I'm still struggling with a bit is stability at wide open throttle. With the mercury (which had a sportmaster unit) I could use properly timed wheel input to work her out of a rhythm of oscillation without having to pull back the throttle. I haven't been able to get the same technique down with this new setup. I've been reading that this engine with the power steering requires a power/pressure bleed process and I'm going to pursue that to see if that give me more control when she's running up and out. It is a difficult thing to sort out and it's not like I can just stroll to the back of the boat and take a look when I'm doing 67 mph... ; )

[powerabout]

Go pro?
Does BRP give a recommended max speed for a g2 which would be criteria for the steering for sure and maybe the gearbox?

[baja200merk]

Make sure the steering is as tight as possible. The g2 Gearcase diameter is substantially larger then a sportmaster but a sporty really shines above 80. So neither case is ideal for your boat. I would also try addding a bit of torque tab to the g2 case. I added one to my m2 case (similar to g2) with jb weld stick and it helped a bunch but it ran 100+.

[blackeye]

I never heard anything about a max speed. BRP claims that though the lower unit on the G2 is bigger it is somehow more hydrodynamic. I've seen some testimony from G2 owners with power steering like I have who get to speeds over 70 and have been very happy with them with no mention of stability issues at the high end. I would love to hear from other G2 owners who are going high 60s and above with their rigs. Before I bought my unit, I spoke to someone at BRP who owned a G2 for his bass boat and said his only regret was that he didn't do the power steering and that influenced my decision to go with the DPS as Evinrude calls it.