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

[Hayden]

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?

[Bmac]

Just curious if you use cruise while surfing? If I have my cruise on I can’t 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.


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[Holdmybeer]

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.

[jnr4817]

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?

[Holdmybeer]

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.

[SONIC]

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.

[jnr4817]

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?

I just got home from lake. I over estimated my rpms.
11.0 is 3200 and 11.6 is 3600.

[Hayden]

Partial crosspost here but it's related to safety/durability so I believe it's worthwhile:

I missed this in the user manual (is it in there??) but from this point on, I will always have engine at 2k rpm when filling or draining G6 ballast. When running heavily weighted, your fill times bump up to almost double, you need the alternator to be 100% assisting with this. (I would occasionally, just run the boat to middle of lake and fill while at only 700 rpm (idle). I don't think you can do it like that, has to be higher ie. 2000 rpm.)

[Hayden]

Just curious if you use cruise while surfing? If I have my cruise on I can’t 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.

This sounds like you're hitting the limit of engine/elevation/ballast/propeller, no? There shouldn't be an rpm limiter at 4000 rpm.

[Bmac]

Sorry I don’t want to hijack this thread but you all have me questioning myself. If I have my cruise on my boat will not go above 4,000 RPMs. There are often times I just need to rev to 4200 to get up to speed but my boat won’t do it. Am I up in the night? I just figured it was a safety feature.


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