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  1. #1
    Join Date
    May 2017
    Location
    Alberta, Canada
    Posts
    176

    Default Heavily Weighted (6500 lbs) Ballast - Engine Wear & Additional Maintenance

    I've finished installing some custom ballast and put on a new propeller to help with the extra weight. After talking to Indmar about engine wear, they suggested I try and get through to Aaron/Roger at Skier's choice service/warranty, but so far I haven't been able to talk to them, (left messages).

    Aside from increasing the frequency of oil changes, and generally being more vigilant about all of the boat maintenance tasks, (fluids, etc.), I'm trying to get feedback on what other tasks or things I should be watching for when running a heavily weighted boat.

    The goal is to get as close to nameplate (4000 + 2500 = 6500 lbs) as possible. I've put on a 15x12.5 Acme and we're at 2800' elevation with the Raptor 400 and running a 10 degree pitch for my wave (Wake9 settings). The boat is performing well, but with this lower pitched prop we're bumping up to 4800-5000 rpm to hold 11.2 mph.

    Talking to Indmar, they didn't seem to think it was an issue at all but also noted that Skier's service/warranty would be the better people to discuss it with. Reading the Indmar manual it mentions that it has built-in rpm cutouts but I wanted to try and get a sense of where the "too much" line was from those who've gone this heavy (or more).

    Anyone have some solid feedback to give on this?
    2021 Mojo, 6.2L Raptor 400 1.76 trans, Acme 2775 15x12.5, G6, Flow3, 6500 lbs ballast
    2005 Mobius LSV (sold)
    Windermere Lake, B.C., 2800' Elevation

  2. #2
    Join Date
    Nov 2019
    Posts
    27

    Default Heavily Weighted (6500 lbs) Ballast - Engine Wear & Additional Maintenance

    Just curious if you use cruise while surfing? If I have my cruise on I cant get above 4,000 RPMs. I am assuming that it is built in that way to protect the motor from running any higher for long periods of time. For reference I have a 2020 max with a 400 at 5,000 ft. I have 5500lbs of ballast and only struggle getting to speed when surfing port side. 15.5x14 prop.


    Sent from my iPhone using Tapatalk

  3. #3
    Join Date
    Jan 2021
    Location
    Columbus, Ohio
    Posts
    590

    Default

    I did not realize elevation was that bad of a performance killer for your '21 mojo.

    I have a 2015 Mojo 400 with 1.5 trans and 15x13 prop.
    Went surfing with full ballast plus lead at 4000#.
    People, gear and fuel was right around 2000#
    Boat weight on scales with no fuel, no gear, and no lead is 4148# (had to go through scales for trailer tag).
    so 10K all the way in water.

    I can run 11mph like this at 3200-3500rpm at 900 ft elevation. Is the starboard tab at 100% down, creating that much more drag surfing port? If you only go to 60-70% can you get the same wave and not have to run near 5000rpm?

    I would think at a minimum you would be changing oil every 25hrs instead of 50hrs and maybe spark plugs every season (if not sooner). Same goes for v-drive and trans oil changes also.

    And please don't take offense, just comparing my experience at no elevation to yours. Just surprised more than anything.
    2015 Moomba Mojo Surf Edition
    4,000lbs
    Manual Flow

  4. #4
    Join Date
    May 2020
    Location
    Nashville
    Posts
    170

    Default

    Interesting. My 2018 Mojo with 400 is loaded with 4780# ballast plus fuel and at least 2 adults every trip. I’ve got oj945 prop, 500 feet elevation. At 11.0 it’s 3600 and 11.6 it’s 4200, I aim for 10* pitch.

    @hayden what custom ballast did you install?
    Last edited by jnr4817; 07-15-2021 at 01:36 PM.
    2018 Moomba MOJO
    4100lbs. ENZO's, Center Tank, IBS
    680lbs. Lead Wake
    Raptor 400
    Surf Prop: OJ 945
    2019 Ford F150 FX4
    5.0L V8

  5. #5
    Join Date
    Jan 2021
    Location
    Columbus, Ohio
    Posts
    590

    Default

    I know there was a hull change and that is also something to take into consideration from my 2015 to 2018 to 2021.

    I am wondering if this is part of the drag issue also.
    2015 Moomba Mojo Surf Edition
    4,000lbs
    Manual Flow

  6. #6
    Join Date
    Aug 2020
    Location
    Middle Tennessee
    Posts
    599

    Default

    5000 does seem really high.
    My SA is heavier than the Mojo by 1000 lbs and I surf 3500-3900 from full stock ballast +600lbs of lead and then depending on people from 500-1500 additional people weight. (16x15 prop)
    You're about 1800 ft higher than me.

    Can you come back up in pitch and go up in diameter to 16"? You may want a little plate on the bottom to avoid gel burn.
    2020 Supra SA

  7. #7
    Join Date
    May 2017
    Location
    Alberta, Canada
    Posts
    176

    Default

    Quote Originally Posted by Bmac View Post
    Just curious if you use cruise while surfing?
    I do use cruise, yep. 11-11.4 works pretty good for us so far.

    Quote Originally Posted by Holdmybeer View Post
    Is the starboard tab at 100% down, creating that much more drag surfing port? If you only go to 60-70% can you get the same wave and not have to run near 5000rpm?
    I’m running 10deg pitch and 60/70 port/stbd for the surf tabs. No offense taken! Looking for constructive feedback.

    Quote Originally Posted by jnr4817 View Post
    @hayden what custom ballast did you install?
    I upgraded the stock rear 1400 lb bags with fatsac rear bags 1800 lb. I will post a video and a pdf explaining the measurements.

    Quote Originally Posted by SONIC View Post
    Can you come back up in pitch and go up in diameter to 16"? You may want a little plate on the bottom to avoid gel burn.
    I measured the altitude/surf prop (OJ 930 15.5x15) before I put the new prop on and I barely have 1” clearance with 15.5. I also called Nettles and talked to them about it and they mentioned that whenever they’re doing their measurements on OJ props, the listed number is always ” over what it actually is. They said the RPM’s would go up for sure with the lower pitch but it would give me what I need to get the boat on plane, (the stock OJ 930 15.5x15 could not hit 11 mph).

    Couple points I’ve found in my testing also:
    1) I was seeing a shift of 500-600 rpm gain going from 10.8 to 11.4mph
    2) The 10 deg pitch really makes the boat work, if moved weight to the front and pitched down to 9 deg or even 8.5 deg the rpm’s would come down as well
    Last edited by Hayden; 07-15-2021 at 02:25 PM.
    2021 Mojo, 6.2L Raptor 400 1.76 trans, Acme 2775 15x12.5, G6, Flow3, 6500 lbs ballast
    2005 Mobius LSV (sold)
    Windermere Lake, B.C., 2800' Elevation

  8. #8
    Join Date
    Aug 2020
    Location
    Middle Tennessee
    Posts
    599

    Default

    Quote Originally Posted by Hayden View Post
    I do use cruise, yep. 11-11.4 works pretty good for us so far.


    Im running 10deg pitch and 60/70 port/stbd for the surf tabs. No offense taken! Looking for constructive feedback.


    I upgraded the stock rear 1400 lb bags with fatsac rear bags 1800 lb. I will post a video and a pdf explaining the measurements.


    I measured the altitude/surf prop (OJ 930 15.5x15) before I put the new prop on and I barely have 1 clearance with 15.5. I also called Nettles and talked to them about it and they mentioned that whenever theyre doing their measurements on OJ props, the listed number is always over what it actually is. They said the RPMs would go up for sure with the lower pitch but it would give me what I need to get the boat on plane, (the stock OJ 930 15.5x15 could not hit 11 mph).

    Couple points Ive found in my testing also:
    1) I was seeing a shift of 500-600 rpm gain going from 10.8 to 11.4mph
    2) The 10 deg pitch really makes the boat work, if moved weight to the front and pitched down to 9 deg or even 8.5 deg the rpms would come down as well
    Gotcha.
    Yes lower pitch will be higher RPMs but I don't know why you'd go down in diameter that gives less surface area, easier for the motor to turn it but less efficient overall.
    Personally I'd go to a 15.5x13.5 or so and see how that does.

    You're under warranty so running 5k doesn't really matter much at the moment but if you plan to keep it long term those numbers would bother me, that's running the engine near full load very near redline for long periods of time.

    1" of clearance is plenty. 3/4 is fine 5/8 is pushing it but I ran my last boat with 1/2" clearance without issue. Long term it would probably pit the gelcoat without some protection though.

    I only see 800 extra lbs of ballast, where's the other 1700? People?
    2020 Supra SA

  9. #9
    Join Date
    May 2017
    Location
    Alberta, Canada
    Posts
    176

    Default

    Here is a vid of the custom bag size difference:
    https://www.youtube.com/watch?v=XoNT...l=HaydenBreeze

    Here is a vid of the bag placement and piping/venting:
    https://www.youtube.com/watch?v=STAF...l=HaydenBreeze


    Hopefully get some wave footage when I go out tonight/tomorrow.
    2021 Mojo, 6.2L Raptor 400 1.76 trans, Acme 2775 15x12.5, G6, Flow3, 6500 lbs ballast
    2005 Mobius LSV (sold)
    Windermere Lake, B.C., 2800' Elevation

  10. #10
    Join Date
    May 2017
    Location
    Alberta, Canada
    Posts
    176

    Default

    Quote Originally Posted by SONIC View Post
    Yes lower pitch will be higher RPMs but I don't know why you'd go down in diameter that gives less surface area, easier for the motor to turn it but less efficient overall.
    Personally I'd go to a 15.5x13.5 or so and see how that does.

    I only see 800 extra lbs of ballast, where's the other 1700? People?
    The prop was cheap and available, so we grabbed it rather than waiting for something to be shipped across the border. Our water level is already dropping and with the heat we had at the end of June, many are worried the season won't go far into August. It was the quickest solution but I agree, not the most efficient.

    Check those vids I posted, they show where all the other weight is going (2x 400 midships, 2x 150 bow, 500 leadwake).
    2021 Mojo, 6.2L Raptor 400 1.76 trans, Acme 2775 15x12.5, G6, Flow3, 6500 lbs ballast
    2005 Mobius LSV (sold)
    Windermere Lake, B.C., 2800' Elevation

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