GN boats in action......

[2manymustangs]

The GN24 looks great with the flames!

I love that GN47 boat though, that paint scheme is super nice, what a great looking 21'r.


2MM, what's the HP on the GN24/47 boats?

Btw, that's for all the great pics!

HP? I would only be guessing but I would GUESS that these guys are in the 800-900 neighborhood... UNless it has Paul Grichar power, then it is MUCHO higher... Kidding about that, kinda... GN7 BOB would be a better one to ask but I do know they run pretty high PSI manifold pressure for what they do...

The GN class is my absolute favorite of all the classes, when you know a little about building engines and then see what kind of torture these guys endure in the LONG runs, with such a heavy hull, in comparison to a K or an SS hull... These guys could break an ANVIL in these boats, its some serious torture and GN7 had the whole engine combo figured out... Going fast is cool BUT finishing the FINAL is even cooler, there is MAJOR fallout in this class due to the torture...

The first time I heard the Plan B 305 boat really crack on it I got an erection like a 18 yr old kid...

[gn7]

HP? I would only be guessing but I would GUESS that these guys are in the 800-900 neighborhood... UNless it has Paul Grichar power, then it is MUCHO higher... Kidding about that, kinda... GN7 BOB would be a better one to ask but I do know they run pretty high PSI manifold pressure for what they do...

The GN class is my absolute favorite of all the classes, when you know a little about building engines and then see what kind of torture these guys endure in the LONG runs, with such a heavy hull, in comparison to a K or an SS hull... These guys could break an ANVIL in these boats, its some serious torture and GN7 had the whole engine combo figured out... Going fast is cool BUT finishing the FINAL is even cooler, there is MAJOR fallout in this class due to the torture...

The first time I heard the Plan B 305 boat really crack on it I got an erection like a 18 yr old kid...

Manifold pressure is not that high. In fact its pretty low. Compression on the other hand, we don't discuss even among friends.
You need to bring 1000-1100 HP to the table, or you are back marker, and they only have 475 inches to make that, with roughly 10 psi boost. They are stressed.

[FormulaZR]

Manifold pressure is not that high. In fact its pretty low. Compression on the other hand, we don't discuss even among friends.
You need to bring 1000-1100 HP to the table, or you are back marker, and they only have 475 inches to make that, with roughly 10 psi boost. They are stressed.

Making that much horsepower with the CI/PSI you have...seems like the static CR would be kind of in the N/A pump gas type range?

[gn7]

Making that much horsepower with the CI/PSI you have...seems like the static CR would be kind of in the N/A pump gas type range?

Yep. Cylinder pressures are stupid. Specially when you consider a roots goes to full boost on the hit, regardless the RPM. So coming off a corner in one is hell on the lower end. Even at Puddingstone where Bill never lifts, in the corners the engine is pulled down about 2000 RPM by the boat being deeper in the water plus the rudder blocking the prop. Full load at 5000 thru the whole corner just torments the crank and rods. That is the only place we ever tore the snout off the crank.

[2manymustangs]

Yep. Cylinder pressures are stupid. Specially when you consider a roots goes to full boost on the hit, regardless the RPM. So coming off a corner in one is hell on the lower end. Even at Puddingstone where Bill never lifts, in the corners the engine is pulled down about 2000 RPM by the boat being deeper in the water plus the rudder blocking the prop. Full load at 5000 thru the whole corner just torments the crank and rods. That is the only place we ever tore the snout off the crank.

This is why I have such respect for the GNs, I recognize it takes a planning and skills to put one together AND keep it together, MORE than in the other classes that make 5 laps and are done...

[Sharp shooter]

MORE than in the other classes that make 5 laps and are done...

Done? You make it sound like they go home after 5 laps.... What about testing, heats, semi's and the final? And keep in mind that many of the GN boats aren't running the entire race at "full" throttle.

I'm not saying your point is wrong, but give the other classes a little more credit.

[2manymustangs]

Done? You make it sound like they go home after 5 laps.... What about testing, heats, semi's and the final? And keep in mind that many of the GN boats aren't running the entire race at "full" throttle.

I'm not saying your point is wrong, but give the other classes a little more credit.

No, no, no, no, I didn't mean it like that at all... No DISrespect for the K's or SS/PS or cracker class is meant in any way...

It's just that the GNs are my fave and partially due to the abuse that they endure and the water conditions that they can run in...

Watching TY and Robbie in the SS shootout of the century at Long Beach, gunnel to gunnel lap after lap, two years ago was like poetry in motion, The crazily overpowered K's are amazing and wild... BUT the GNs and the conditions they endure are amazing to me...

[FormulaZR]

Yep. Cylinder pressures are stupid. Specially when you consider a roots goes to full boost on the hit, regardless the RPM. So coming off a corner in one is hell on the lower end. Even at Puddingstone where Bill never lifts, in the corners the engine is pulled down about 2000 RPM by the boat being deeper in the water plus the rudder blocking the prop. Full load at 5000 thru the whole corner just torments the crank and rods. That is the only place we ever tore the snout off the crank.

I guess I have lot of questions about the engines...how do you control detonation? I mean, all I can think of is backing the timing down or run pig rich....but if you did, you'd never crest the 1k hp mark. Very high octane?

[gn7]

I guess I have lot of questions about the engines...how do you control detonation? I mean, all I can think of is backing the timing down or run pig rich....but if you did, you'd never crest the 1k hp mark. Very high octane?

Lot of water flow thru the heads with a few tweeks to keep them as cool as possible. Piston oilers to keep the heat down in them along with a with other things I don't really care to reveal online, and yes, C16 fuel.

[Sharp shooter]