Propping my 311
 

What's up folks?!

I've been going through the 311 working on upgrades here and there (sound system, LED lighting, cleaning cleaning cleaning), and now that the warm weather looks to be here to stay we're really starting to have some fun with her!

One observation that I wanted to bring up is around getting the props right. I know that this has been gone over quite a bit already, but my boat seems to be a bit of an anomaly in the fact that she has a pair of Gen VI 502 MPIs mated to B/W 72C transmissions and TRS drives. I'm thinking that power-wise, she's somewhere in between the output of a set of 454 mags and the original 420s she came with (but with more torque than either set up). Ted G and I were already discussing this some on Facebook, but I though I'd open it up top a wider audience. Now this could be that I do not have the boat trimmed out all the way (my last run I flat out ran out of room), but with the 23P solid hub Mirage props that I'm running, I'm hitting the rev limiter at 5200 and seeing 64 MPH on GPS. She may have been climbing a little more, but like I said I ran out of room. I see 420s running right around 70 at that RPM and the same prop; I'm seeing 16% slip with mine while the 420 sees around 9-11%. I'm trying to wrap my head around why? Regarding trim, I know that as I was running her, trimming would bring up the RPM so I know it was having an effect (that's how I got to the rev limiter). I don't think these things make much power over 5K RPM so having them up that high is a waste. I'd think though that RPM is RPM and that if she could spin to 5200 with the 502s that she'd get pretty close to what the 420s were doing. Formula says the boat should go a tenth or two under 70 with a 502, but I believe that's with a Bravo (I do not think there were any 502s in front of TRS drives made).

My thinking is to bring the RPM down to 4800-4900 with either a set of 25P Mirages or maybe some 4-blades. I have access to a set of 27P Mirages but they may be a bit too much. Distant Thunder has offered up his 26P Bravos to try in the next couple weeks.

Any thoughts?

My 357 had TRS with the O.E. 420's that got stroked. It had 24 bravo1 props.
Maybe the 26's could work with your shorter boat.

Definitely going to try them.

Anyone have comparisons to how the 502 runs versus the 420? I'm assuming there's more toque available because of the 48 CID difference.

My 272 with 330s ran 4500-46rpm 64-65 with 25 mirages, non plus so 9 to 10 percent slip.

My 311 ran 70 at about 5200, 5250 with 23 mirage plus, so 9% slip or so. 420s with roller cam upgrade.

Are you running plus or non plus 23s? I think you should be at about 68 with your setup. The trs is a bit slower than the bravos. For some reason your slip is a bit high for a twin but there should be 4mph left in there. Are the engines strong? I know you had some firing order issues but how were the leakdown numbers?

The props are 23 Mirages, not pluses.

The engines are good. I never did the leakdown tests. They ran (and continue to run) so well that it seemed pointless. After finding all the stuff that was deliberately done to mess them up, just wasn't necessary to do anything else but run them. The boat gets on plan with no issues and accelerates hard. RPM is RPM. If something was up with them, I think we'd be chasing it in the other direction. In my opinion she's about 3-400 RPM over-propped. The question is why?

To clarify... I would think that the 420 would have a leg up over the 502, but perhaps not in the the RPM range that it operates.

The pluses have more cup and bite harder than the non pluses. What are you trimming to? I want to say mine drives are level at about 3.5 and i trim up to 7.5ish wide open

Honestly, I'm still trying to get that all figured out. The drives are level at 3; she was climbing RPM with trim and then hit the rev limiter. No matter how she's trimmed she' reachs 5K RPM with no hesitation.

I'm not as concerned with the top-end as I am with cruise, but having a solid 69-70 MPH boat is a plus... not that it's anything to really brag about these days but still!

I hear ya, just throwing some ideas out. My boat was about a mph slower with 25 pluses. But as you have said you may have more torque to turn them. If you were closer you could try mine.

Your under propped hitting the rev limiter.

No way toknow how fast it will go with hitting the limiter.

502MPI's run fastest if I remember right, right at 5,000rpm and OE rev limiter is 5150.

Agreed. I'm going to try some different props.

I believe my 502s are stock with exception of the exhaust (CMI E-Tops) so I'm surprised that the 502s seem to have a good amount more a$$ to them compared to the hotter 454/420. I guess displacement and torque win!

My old 420's were stroked so their performance was not a normal comparison to a 502 due to having more stroke which helps produce torque big time. Stroked the same I would still give it to the larger displacement.

Sounds like 25 pluses to me Tom

I ran 25 mirages on mine. I did try label 25 plus but that was not as good. the TRS boats have the props deep in the water so they tend to like the smaller diameter of the non plus props. I would try a 25 mirage and see how it goes from there.

Mine runs best with 25P Non Plus

My stock 420's could spin my 23 non plus props to 5600 rpm but slip wouldn't let it break 70 mph. Ran it that way for a year and found some 25 non plus and have been running them since.

The best I had was a 25 B-blades labbed plus. I just never could pull the trigger on the cost. I may have a set that I took off my boat when I sold it if you are interested.

These boats with TRS anyhow like a LOT of trim. It is crazy that the more you trim the faster they will go. They never seem to blow out. The issue if you trim too much is you will chatter the gear set and blow the lower unit... Don't ask how I know but I hear they will go a bit over 74! LOL

What have you got?

Blowing the lower unit doesn't sound fun at all! Trim angle causes too much stress I take it?

I blew a lower right in mine at 75, pulled back on the throttles as the engine wung past 6k. Not much fun.

I take it then that the failure is RPM related?

With mine when the gears let go it allowed the motor to over rev, so not because of rpms i dont think.

I've had drives let go.... unfortunately pretty familiar with that!

I guess with the TRS... trim and angle and load/rpm are the issue? TRS drives are new to me... trying to understand their weak points (if any).

Uppers are pretty much bullet proof. The lower lefts seem to be too. Only problem ive had is one lower right let go. They seem to be the weak point. The driven gear is behind the pinion instead of in front of it like the left and less supported.

The carrier bearing on mine was corroded, so i bought a corrosion free right hand drive and blew it in 17 hours, put the corroded one back on for now with no issue. Maybe that drive had a prior issue.

I had a 89 311 with TRS drives and 420hp motors. I don't know what it was about that boat but it sat a lot higher in the water then the one that my buddy had that was the exact same set up. I have since sold that boat.

TRS drives like to be deep in the water. They DO NOT like to have the prop surfaced. When you trim it way up the prop starts to capitate and they blow the gears. This is what I did being stupid. It did hit 74 GPS however LOL I think if you get between 68 and 70 then I would be REAL happy.

They are great drives. Love the way that they shift. They are well with in the rated power. The only thing I would say is don't mash the throttles out of the hole and don't way over trim them and you should be good. They are for the most part very strong drives for your set up.

Update!

Test data...

27P solid hub Mirage props. Not in perfect condition.

Max speed of 67-68 GPS at 4600-4700. I ran out of room where I was testing, and the 'Bay was too rough to play in this afternoon (managed to run 54-55 MPH in five footers when I was out there... big storm coming in).

I am loving the cruise speed... in the 50's at 3300.

Thinking of having the props cleaned up, and removing an inch of pitch... 26P Mirages. That would put me at 4800-4900. Current slip numbers at are 15%.

Should I go this route?

On thinking about it... was probably three to four footers with some deep holes here and there. I got about two miles out and thought it would be best to come back in... the ride back was a soaker!!

You're getting closer Tom! Great news!

Man that 311 looks great in the water. The proportions and stance are perfect. Funny how a couple feet can make such a difference.

I really love the boat!

The coolest thing is all the positive attention she gets when we're out. She definitely doesn't show her age!