DavisIslander Posted October 18, 2019 Report Share Posted October 18, 2019 Having a great time with my 04 RF18 and my mis-firing went away (knock on wood)...hopefully. Hauling back to the ramp the other day I checked my rpm's and speed and I thought it was great. '04 115 4 stroke with a no-name 4 blade SS prop. WOT is 4600 with 33mph. However, reading over the WOT literature I'm seeing it should be 5000-6000 for my model year engine. Does it really matter? I always back off slightly and still cruise at a wonderful 30+. I'm not buying a new prop until I need one (knock on wood again) and everything else is ducky!http://mbgforum.com/forum/73-hewes-prop-discussion/?do=add# IMG_1042.MOV Quote Link to comment Share on other sites More sharing options...
HoneyB Posted October 18, 2019 Report Share Posted October 18, 2019 I think props could get the rpm up but 115 on a 18 Redfisher might not see much more speed. It probably loves the 4 blade prop to get her out of the water and keep it riding high Quote Link to comment Share on other sites More sharing options...
DavisIslander Posted October 18, 2019 Author Report Share Posted October 18, 2019 26 minutes ago, HoneyB said: I think props could get the rpm up but 115 on a 18 Redfisher might not see much more speed. It probably loves the 4 blade prop to get her out of the water and keep it riding high Exactly! Nothing to worry about here, I love my boat and it's perfect for me! Quote Link to comment Share on other sites More sharing options...
lurem Posted October 18, 2019 Report Share Posted October 18, 2019 Imo, you need to be up 1400 RPM's and running 45 mph. That's just me, I like to get the max performance from everything I drive. If you are happy with the RPM's and speed then leave it be. dc 1 Quote Link to comment Share on other sites More sharing options...
DavisIslander Posted October 18, 2019 Author Report Share Posted October 18, 2019 19 minutes ago, lurem said: you need to be up 1400 RPM's and running 45 mph. 15 more mph? Wow! I'm not sure how to accomplish that - gonna take more than a new prop. *** - 45 is eye-watering speed. Quote Link to comment Share on other sites More sharing options...
HoneyB Posted October 18, 2019 Report Share Posted October 18, 2019 So to speed up you have to have the power to turn props to higher RPM. If you lower the pitch the rpms will go up but that’s not going to corollate to 14 mph faster. yes there probably are gains in mph that could be had. But you have to be willing to do the dance. Quote Link to comment Share on other sites More sharing options...
geeviam Posted October 19, 2019 Report Share Posted October 19, 2019 Lurem is right. Your RPMs are too low (most likely over-propped), so your motor does not have a chance to develop its maximum horsepower. Speed may not be important to you, but the extra strain on the engine would be a consideration, if it was my rig. An outboard motor pushing a boat is similar to your car's engine pushing the vehicle uphill constantly, with a single-gear transmission. With a prop that is too large (or has too much pitch), your outboard is always pushing the boat uphill in high gear! Fuel economy should improve with the correct prop as well. Your 4-blade prop is probably a 19 pitch, or higher, when it should be closer to 16 pitch, or less. If you want expert prop advice, ask Marcus at PowerTech Propellers (aka Funky Monkey on this forum) for a recommendation. Just my two cents. Quote Link to comment Share on other sites More sharing options...
HoneyB Posted October 19, 2019 Report Share Posted October 19, 2019 Looking at a couple of charts I see the 90 and 115 two strokes rpm range to be 4500 to 5500... at 4600 I would agree there probably is a prop better suited for your rig. Since you stated your not wanting to spend money on a new prop there is not a lot to debate. 4600 is on the low end but in the operating range suggested. Yes personally I would tinker my butt off to max rpms out. Once max rpm is achieved you know the mid range economy is as good as it can be. But if your plumb happy with the set up don’t go down the rabbit hole of prop testing. Quote Link to comment Share on other sites More sharing options...
geeviam Posted October 19, 2019 Report Share Posted October 19, 2019 6 hours ago, HoneyB said: Looking at a couple of charts I see the 90 and 115 two strokes rpm range to be 4500 to 5500... at 4600 I would agree there probably is a prop better suited for your rig. Since you stated your not wanting to spend money on a new prop there is not a lot to debate. 4600 is on the low end but in the operating range suggested. The OP stated it's a 4-Stroke 115 Quote Link to comment Share on other sites More sharing options...
HoneyB Posted October 19, 2019 Report Share Posted October 19, 2019 Wow, it is a four stroke ... and I went back and read the year model a couple of times. I stand corrected on the 4 stroke. Quote Link to comment Share on other sites More sharing options...
DavisIslander Posted October 24, 2019 Author Report Share Posted October 24, 2019 Thanks Guys! I plan on keeping this motor/boat for a long time - "until death do us part", so in 2020, I'll make the investment in a newer (More appropriate) prop. As it stands now, gas mileage is super and hole shot excellent, but with less than 400 hours on this 04, no need to add constant strain. On 10/19/2019 at 12:39 AM, geeviam said: Your 4-blade prop is probably a 19 pitch, or higher, when it should be closer to 16 pitch, or less. If you want expert prop advice, ask Marcus at PowerTech Propellers (aka Funky Monkey on this forum) for a recommendation. Just my two cents. I will definitely do that! Too much strain is NOT a good thing, especially with the frequency of me taking this baby out. Thanks all! 1 Quote Link to comment Share on other sites More sharing options...
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