I know it’s not the same dyno, so not an exact comparison, but the R seems to make in between what the X and XS made...
http://www.davebushracing.com/mercur...0x-update.html
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I know it’s not the same dyno, so not an exact comparison, but the R seems to make in between what the X and XS made...
http://www.davebushracing.com/mercur...0x-update.html
Torque is on an R is way more then an X or XS and probably close to what a 3.6 XS is. They are an incredible piece that runs on anything more then swamp gas.
Joe
Any idea what the tq and hp numbers are on the 300 sea pro? Do the base seapro and xs have the same Length intake runners? Thx, Rm
There is a thread on here about the the prop shafts. They (merc.) are well aware of everyone that breaks (it cost them a ton of $$) to cover warranty claims when expensive propellers are lost in the process. The fix for this adds additional cost to the company which changes product profit estimates etc. etc. etc. and when you are owned by a massive corporation, anything that changes production processes and or alters profit forecast becomes a process of signatures and approvals to be implemented-much like the US congress, nothing happens fast. Its just part of operating with thousands of armchair warriors, board members and stock holders that look at paper and numbers to gauge their success.
You can guarantee that if the guys on the front line could make the call it would have been done before the fourth or fifth one broke.
Joe
According to the Carb report below 300 SeaPro is detuned to 276hp@5500 and 298ftlbs@4500. Yes all 200-300hp V8s besides the 300R share the same parts except the throttle body, the 200-225 uses a smaller throttle body and the 250-300 gets the larger one. The rest is up to the computer tuning, the peak hp numbers of the 250Pro XS is the same as 300 Sea Pro for example though the 250 Pro XS makes 312ftlbs at the same Rpm.
https://ww3.arb.ca.gov/msprog/offroa...w-001-0490.pdf
I agree, the 4-stroke will be easier to prop for holeshot. A properly propped 2-stroke that ventilates to the powerband would still give it a good run I imagine. It’s like a big block that doesn’t need a loose converter, but the hotter small block makes the same peak torque it just needs a higher stall to cut the same 60’. Once they’re moving down track, the hp as you said is what’s going to determine the top end speed.
No, they’re the same part#s as can be seen below. Only the 300R has different cams, the two different size electronic throttle bodies 64mm and 80mm are what ultimately are limiting the amount of air able to be ingested which determines the peak hp number and why the lower hp engines peak at lower rpm than the higher hp ones as they’re essentially an airflow restrictor.
https://www.mercurymarine.com/en/us/.../parts-catalog
I would look at cam times as well. 3* +- is up to 20-30 hp.
I agree advancing or retarding the intake cam 3* would change the output and shift the powerband up or down ~300rpm as that’s how Yamaha does it on the SHO with VCT, but Mercury chose a simpler/more reliable design in my opinion which I applaud with fixed DOHC. Being this is engine has an electronic throttle body like the SHO to limit airflow like it’s counterpart does as well for it’s 200-300hp versions of the same 4.2L V6. My guess is Mercury then uses torque based engine management to keep the powerband flat from peak onward with the lower hp models as noted in the carb reports. This keeps the engine from needing to be propped lower if the intake cam was only advanced to lower peak output as that would only cause the powerband to fall off faster at higher rpms resulting in a boat that wouldn’t run as fast on the top end. Torque based engine management has been around in the automotive world for some time...
https://www.sae.org/publications/tec.../2001-01-0269/
Variable valve timing will be coming at some point "assuming the market is willing to pay for the horsepower that it will be capable of creating". We are just seeing the tip of the iceberg for this platform.
Joe
Agreed, it’ll help with emissions as well which unfortunately is going to continue to play more of a factor with the feared climate change propaganda. Making more power is easy these days, but stipulations make it more challenging and the complexity then adds cost as you’ve alluded to. The other thing that is not as big of a deal in the automotive world, but is in the outboard industry is weight. I’ve always been a fan of natural aspiration over forced induction weight being one of the reasons as well thermal, efficiency and the linear powerband. With more cubic inches comes more fuel burn and more RPMs creates more heat, so there has to be a balance. For reference the 350 Verado only makes 25hp and 9ftlbs more (341hp@5800 and 320@4500ftlbs according to CARB report) than the 300R, but weighs 156lbs more...
https://www.arb.ca.gov/msprog/offroa...w-001-0477.pdf