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Thread: 300R Prop Help
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12-21-2020, 11:23 PM #31
I have a 250 ProXS V8 with the TMII lower on my Key West 210BR (19 degree, pad bottom, 4 lifting strakes. It’s a very fast bottom for a CC) and it likes the B1 FS 23P. Runs 72 @ 6200. Amazing acceleration and cruises really nice at 55 mph turning around 4800 rpm. Not too shabby for a fishing boat . According to the factory it’s one of the fastest Key West’s on the water.
I did have to plug the top 2 holes on each side to get Max water pressure where the prop likes to air out but the TM has low water pickup in addition to the 5 side holes. Not sure I’d go as radical as Joe, that’s not a lot of flow for a big V8 IMHO. I get about 23lbs of water pressure at any speed above 50. Motor runs 138 degrees water temp at WOT.
The FS props are interesting, the castings are all even pitch so the lab adds cup to get the 23P so it’s a soft 23. The 24 is pretty spot on so you will see a bit more drop in RPM from 23P to 24P than normal. They also need to run about 1.5” higher than the Rev4 or Tempest Plus. It should be enough diameter for the 5.44 lower but I don’t think you can get your motor high enough without plugging some holes. You may want to consider a prop that’s made to run completely submerged like a base Bravo 1 or a 3 blade Tempest Plus 23P.Last edited by mjw930; 12-21-2020 at 11:41 PM.
Mark
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12-21-2020, 11:41 PM #325000 RPM
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Thanks for the explanation. I have a lot to learn on the logic used on the DTS engines. Unfortunately my 300R is a DTS. Let's assume for arguments sake, that at WOT my TPS sensor is reading 4.8V to 5.0V (just a guess based on some of the stern drives I have worked on, not outboards). Can I probe the wires to the TPS, turn the ignition on, and open the throttle blade by hand and read the voltage read out when the throttle blade is fully opened manually moving the TPM to its furthest travel and highest voltage? In other words if it only read 4.0V when I tried this, or some other value below the threshold for the system, then wouldn't I know that I really do have less than 100% WOT throttle?
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12-22-2020, 12:13 AM #335000 RPM
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Is your gearcase the 5.44" HD? I am only asking because the Torquemaster on my 300R only has 3 holes on each side plus the low water pickup holes?
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12-22-2020, 06:09 AM #34
No, there is no relationship between the TPS voltage and Demand throttle. The G3 setup is mandatory for the proper operation of a DTS motor. I did read somewhere of a manual DTS controller setup option but I’d need to dig for it and it’s only yo get it to run, not to provide proper operation. Every servicing dealer has the program so find one any pay for the service. Mercury will also not honor the warranty on a DTS motor if it’s not initialized by a dealer, or so I’m told.
On the gearcase, Mercury made a running change in late 2019 to add 2 additional holes in response to a number of overheating claims from bass boat applications. It seems that many were running in shallows and clogging the low pickups so they added the 2 upper holes to provide more water. The net effect for me was reducing the Max drive height I could run by an inch. I wish I had your case, then I wouldn’t have needed to plug the holes.Last edited by mjw930; 12-22-2020 at 06:13 AM.
Mark
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12-22-2020, 07:09 AM #35\\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\///
Checkmate Pulsare 2100 with a 2017 Merc 250 Pro XS
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12-22-2020, 07:41 AM #36Member
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Mark, the HD gearcase has 8 holes on each side and was thinking maybe closing up 3 or 4 on each side once I get the prop figured out. Hopefully getting the 24P FS by the end of the week and will see how that runs. Will see if I can find a tempest to try.
The boat was new build, should I assume the builder used the G3 to set it up? I live in Lakeland and could make the drive east to come see you.
That Key West is moving out! I don't see why I should not be able to break 70 once I find the correct prop.
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12-22-2020, 08:04 AM #37
Luckily there is virtually no difference in the setup between the two. I know, I have both sitting the driveway
I have a Tempest 23P sitting in the garage so maybe dragging it over or meeting half way like Eustis and doing a prop test session might be in the cards. Always looking to get out on the water when I can.
BTW, the KW @ 70 mph is quite the handful. The bottom design is set up to be optimal at around 50mph since that's considered "fast" by most fish boat standards, Bass Boats excluded. So, the pad and strakes are a bit oversized so it generates so much lift that by 65 MPH I'm basically balancing it on a 10" wide pad. if it had a smaller pad it would sit down a bit on the strakes and be more stable at these speeds. The side benefit is the same boat with a clunky Yamaha 150 I-4 motor runs 50+ which gives them bragging right within the Bay Reef market. It certainly isn't a boat that I would let an inexperienced driver run with this power.Mark
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12-22-2020, 08:35 AM #38Member
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First time I used the boat was Lake Eustis and Lake Harris. About 90 minute drive. Would love to meet you there and hook up the G3 and test that prop. Any excuse to get out on the water while I am in my slow season.
I can imagine the KW at 70 is a handful. The Concept gets loose trying to get the max speed out of her. Off course I have not owned a boat in 12 years and last time was stern drive 91mph boat so totally different. Only have a dozen hours on the boat and that is with 3 different props so still trying to figure her out.
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12-22-2020, 10:51 AM #39
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Boats&Taxes liked this post
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12-22-2020, 06:37 PM #40
So the first thing that needs to happen here is to throw a taller prop at it to get it below 6400. Anything above 6400 will pull throttle to keep it from going above 6400, regardless of whether it's a "mechanical" or DTS. All the mechanical gets you is an 8 lb heavier engine, and the DTS is now on the engine, instead of under your helm, and you get to deal with the idiosyncrasies of cables when you turn and trim. So both engines act exactly the same, one the signal is directly from your hand (DTS), and the other is from your hand, through the throttle lever, cable, over the transom, through the rigging tube, to a potentiometer on the engine, to convert everything back to electrical signal to the engine. Make sense?
As Joe said, the engine is trying to achieve and RPM based on what you are asking from the throttle lever. If you go over 6400 RPM, it will automatically change that request for you to stay off the limiter, and this is where the G3 tool is used for propping with these new engines. You need enough wheel on it to get it under 6400, then work on engine height.
I'd be trying 24P, 25P, and 26P Rev4, and the same with B1 and B1 FS. The Rev4's run really well, and if you don't need the stern lift, 5/8" to 1" off the tube will settle things down out back and usually net a 1 mph gain if you don't need the stern lift.
Hope this helps.A problem is only a problem when viewed as a problem...
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12-22-2020, 06:55 PM #41Member
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Tried Rev 22P, Rev 22P cut down bell and now the FS 23P. With both Rev props the boat ran bow down too much. I should get the FS 24P this week and will get out and test it as soon as it shows up. I hope the 24P brings the rpm down and I then see the speeds that I am looking for.
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12-30-2020, 02:30 PM #42Member
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So I got the Bravo 1 FS 24P and tried in fresh water today in some lakes that were too small so kept running out of room. With full water and fuel tanks I saw 67.9mph at 6,400 rpm. So going from FS 23P to FS 24P dropped me 100RPM and picked up 1.8 mph. I guess I will try a FS 25P next. If I can drop another 100RPM and pick up another 1.8MPH by going up 1 pitch again I will be right at my goal. Slip% is still very high.
Someone told me the 300R makes max hp around 6,325-6,350? Anyone know if that is correct?
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12-30-2020, 04:26 PM #43
You are saying all things were the same and 23 to 24p made that much difference?
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Checkmate Pulsare 2100 with a 2017 Merc 250 Pro XS
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12-30-2020, 04:42 PM #44Member
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Basically yes ran on same lakes and temps were about the same. Only difference was this time fuel tanks were full and last time they were maybe 3/4 full. So if anything that would have hurt me. I was told to expect 1-2 mph increase and that is what I saw. Now just wondering if I would see the same gain going up one more pitch.
Last edited by Boats&Taxes; 12-30-2020 at 04:49 PM.
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12-30-2020, 04:59 PM #45
I'm suspicious of the props only being 1" different... I'm sure somebody else will chime in.
Anyway, that's a Concept to be proud of! Every mile per hour from here is gonna cost you\\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\///
Checkmate Pulsare 2100 with a 2017 Merc 250 Pro XS
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