sporte77

Cavitation vs. trans slipping? Swap out prop to different size before you give up.. Mine cavitated a lot with the stock prop - I swapped out to a 16x13 and no more "slipping" (was actually cavitation) - but totally feels like it's slipping (RPMs go up fast/boat doesn't accelerate). Just a thought to consider - if you haven't already.

I hope this isn't a dumb question from me... But- have you tried a different prop? Are you sure it's not cavitating. I had what felt like slipping when I first got my 2018 Fi21. I switched props (bigger) and it went away. It was the prop cavitating. I now have a 16x13 prop. I've only had it cavitate once - during some rough water on a surf start.

First, you need to see what the trailer manufacturer is. Is it a Boatmate - or Extreme trailer? Mine is an Extreme (2018) and I had to replace the axle and the trailing arm. Lippert Components owns Extreme now - so you could go through them. However, all the trailer axle parts are manufactured by UFP. Soo.... If you knew the model number of the axle - or the trailing arm (and their capacity) - you could buy one on amazon or ebay. Below, I have listed 2 links. I don't know what your trailer is - so these LINKS do NOT (probably don't) fit your trailer - I only posted them here so you could see examples of what you may be looking for. What you need to do is find out the ratings of your trailer. Hub bearing diameters could be different also - so best you can do is get the manufacturer info - OR you could take it to your boat dealer and they can order the parts for you. Heres some examples (but may not be the ones for your trailer) - just to show you pricing, etc, : https://amzn.to/3DexPp4 boat trailer trailing arm https://ebay.us/VnhvnH boat trailer trailing arm Locally, (i'm near Portland oregon) - I've used Potter-Webster for trailer parts. But you have to know what you have before you go in: www.potterwebster.com Here's Extreme Trailers contact info: Extreme Custom Trailers (extremetrailers.com) Here's Boatmate: Boatemate Parts (boatmateparts.com)

Old post - but wanted to update. I’m using 16x13 prop, have 200 hours on the boat now. And getting 5gph average. Seems that between the break in hours and bigger prop- I’ve seen gains in efficiency

Oldish' post - but I ended up installing a Raymarine i40 display and a transom mounted paddle wheel to show true water speed. While you can just add/subtract the 2-3 mph everytime you go up or downstream - this made is easy to just glance down and adjust. I usually start off at speed of 12 for surfing - then adjust shortly after. The install was pretty clean - but tight - because the only place to put the wheel was between the stinger and the plate. May end up having the dealer put in a thru hull wheel sometime - so there won't be as much erratic readings in the chop. I decided to try the transom mount first - because it was the least risk - as far as hole size/screws - vs. thru hull. Also, transom mount was less cost for this experiment.

I did mine using Marine Nano Shop. Easy wipe now. We will see how durable it is after this coming summer is over. Cost me about $300 (plus I bought a couple DA buffers). Took me about a day to polish the previous coat of wax off with MNS's polish & then their wipe down (mostly alcohol). The application went faster, about 6 hours. I had leftovers - so I did my trailer. The stuff goes a long way.

I was told that you can - but you have to have the braces that come delivered with the boat to do it safely. They are black and about a foot long. They screw into the bolt holes on the base of the tower. But I've not done it. Call the dealer - or maybe a dealer can chime in here? Before you do it.

I've been investigating this issue. I am also on the Columbia River. GPS speed is a pain in the A**. Without a paddle wheel, every time we go out - I have to screw with guessing and calculating. On the river, we have tide movements of anywhere from 0-3 mph; we have wind (affecting RPMS); we have current. So, I thought - "I'll just add 1.5mph going downstream & subtract that going upstream. But having driven the Fi21 for 4 months now - I'm constantly screwing with the speed based on time of day (tides) & wind. Changing speed (especially for someone who doesn't drive your boat much) is a pain every time you turn around. Anyway, I think I've found a solution - but Centurion (in my short term as a convert from Malibu) has been mostly unresponsive answering my questions. My dealer is great - but has no idea on this issue - and has the same crappy response times from the factory as I do. So, I usually end up calling Centurion directly. Here's a copy of the email I sent. I think this would work. Of course if I call Murphy/Enovation Controls - they'll just tell me to talk to Centurion. Usually Centurion tells me to call the dealer.... ---------Email to Centurion------------------- "….. questions of GPS vs Paddle Wheel retrofit possibilities on an Fi21.My goal is to disconnect the GPS (because it’s a pain in the river to get a consistent wave due to changing current, winds, tides).Will you please forward this to engineering?Is it possible that Airmar’s UDST800 (ultrasonic speed,depth,temp) could replace the current Airmar Temp/Depth transducer - if we disconnect the GPS puck? That way, the speed input is provided by the transducer instead of the GPS.I think the interface would support it. Please let me know? My alternative is to mount an ugly, stand alone paddle wheel & raymarine i40 display. Yuck."-------- --------------------- Ok - so the basic systems/brains on these boats are a common interface (NMEA, etc.). So, the ZeroOFF boat brain that's tied into the BUS of the display and engine controls shouldn't care if it's "GPS", a paddle wheel, or an ultrasonic transducer that measures speed. It's simply a value that goes into the speed input as a signal. When I called Centurion, one of the customer service guys thought the Fi still has a paddle wheel plug on the harness. He theorized that if you plugged one in - then unplugged the GPS - the system would use that input. I haven't gotten a response from Centurion's engineers yet. I wish they were more responsive. My '12 Malibu had RPM speed and a paddle wheel control - which I could dial my wave in exactly every time. YES, a sunflower seed can stop your paddlewheel. I don't care. When I go under one of our many bridges - my GPS cuts out and the boat almost stops. You all know, your speed is critical to dial in the wave and is sensitive within 1/2 MPH. I know Malibu is a lot bigger and has many more employees (which correlates to their higher price!) - but this issue is something that anyone who operates on a river would PAY to have resolved.

I had the stock 1235. So I chose the 2277 15x15.75 prop (Fi21 -409 - at sea level). Ran it today. It lowered my surf RPMs (mostly full ballast/11mph) from 4100 to 3600. No noticeable loss of holeshot. About 1 or 2 mph increase in top speed. But I know if we go to altitude- I’m going to have to get a 16x13 to bring. So I’ll probably just keep the 15x15.75 on, and get a 16x13 as my spare.

I wanted to start a thread for Fi21 owners who have upgraded their stock prop. I've got a 2018 Fi21 with the PCM L96 (409) engine. My stock prop is the ACME 1235 (14.5x14.25). At sea level, I'm seeing about 4100-4300 RPM surfing w/ full ballast & about 10.5-11mph. Top speed is about 33-34 at 4900 RPM. Also, the holeshot is just fine. Anyone gone with a bigger prop to get the RPMs down? Please share your actual experience.

Wow! 4 gallons per hour. That IS amazing. We must be doing a lot less cruising back and forth to our ride spot. Also, I've heard guys have changed out their stock prop and seen good gains. I'm running the stock 1235 (14.5x14.25) and seeing 4100-4300 RPMs surfing btwn 10-11mph with full ballast. Thinking about getting a bigger prop to drop the RPMs. One other guy said his Fi21 experience is that the fuel consumption goes way up passing 4000rpms. I don't think I should go all the way up to a 16x13 though - I've got the 409 engine and the shaft is 1-1/8" vs. the HO engines that have the 1-1/4" shaft. Maybe look at a 15.5 or 15"

Yep, 23' vs 21'. I'm happy & it sounds like you are too. :-D

Oddly, even using the profile with transom bag zero - it was still filling up on it's own when that profile was activated. So, like I ended up doing with my Malibu, I've reverted to just using the ballast screen. Too many variables (rider levels, people levels, fuel levels, etc...).. But I did end up just deactivating the transom bag through the dealer option screen.