How do I get more out of this thing?
 

My 311 Formula.

You all pretty much know the specs… 509s, AFR 325s, 9.4 comp, Rookie’s 235/241 .650 lift roller cams (using Crane hydraulic rollers), Merlin intakes, custom Demon 1025 carbs, closed cooling, CMI etops, TRS. 27P solid hub Mirages (these came off the Cig Bullet and were on the boat when we got in 2007 - may be labbed but only way to tell would be to send them out).

The engines run super strong. A/F ratios are good especially at WOT. If I want it to, the boat comes out of the hole surprisingly hard and planes immediately (would rather not break a lower though so usually I’m easy on her). From a planing perspective I could probably run a 29P and not lose anything down low.

My problem is too end. We ran into the 70s but we’re hitting a wall at 5k. This was while running the oceanfront Saturday. I couldn’t run a lot of trim maybe only 4 on the card (back when I had the 502MPIs the best speed was with it trimmed off the scale…71-72 with the same props but turning 4700 maybe just under 4800).

The engines are not taxed. Oil temps (thermostatically controlled) however right around 200 degrees and coolant runs about 175-180 except above 60 where the temps drop to 150 (pegging water pressure). They sound great!

So is this just a trim situation? Too much wetted boat? I feel conditions were optimal.. not too hot and just enough swell to allow fast running and get some air under the boat but the ocean can be unpredictable and finding a hole at 70+ would not have been good. I have a pair of 26P Bravos that I won’t be using on the Bullet (too small for the new power). I would think these would be TRS breaking props but I’d be willing to give them a brief try.

Running at dusk after the temps dropped into the upper 60s seemed to make them even happier, but the Bay got rather snotty so we were limited to how fast we could run without getting the boat airborne.

Comments critiques and suggestions welcomed.

You have 3 factors:

Hull and wetted surface /weight

Engine HP

TRS Drive/Prop

For some reason the 80s and early 90s Formula boats have a hard time running fast and need a lot of HP to even get to 70mph. Is this from the weight? Or weight and hull design? One option is to put her on a diet. As an example, I yanked my fridge...don't need it...new coolers are great and contain spills. Have you still got the Formula alcohol dispensers in there??? Lol

How your hull is trimmed out is likely something you've already played with. Different props will have an affect on how the hull behaves.

TRS drives are typically really deep in the water. Have a check with the prop shaft aligned with the hull...how far down is the center of the prop shaft from the hull? Newer prop designs don't need to be as deep. Raising the TRS drives up would reduce a lot of parasitic drag in the water. Water resistance is cubed. Air resitance is squared.

I appreciate the effort of filling in the transom and recutting to raise your X-Dimension, but you are asking what can be done.

You probably already know, the TRS drives don't like 4 blade probs. The re-entry bite on them seems be the culprit. Ha e you got the Bravo 1 shims on your TRS drives? Or the crush to tolerance shim?

Not much you can do about the TRS bullet hydrodynamics. Mixed reviews on nose cones. You can just as easily make it worse.

You've got healthy engines. Why are you limiting them to 4800-5000 rpm? Let them breathe a bit. 1.65 ft lbs of torque is the max NA you can really ever achieve. To get more power, you need to move up the rpm scale.

Obviously, you would need to spring the engine to operate up there if you aren't already. With the 235/241 cam, you likely are not even in the peak HP rpm range at 4800. AFR 325s are healthy heads, no issues there.

The 72c velvet drives are rated for tq not HP. Like most transmissions. Turn them a bit faster, and they have an easier go of it. Obviously, there is a limit.

Didn't the 311s run 60mph with the 330 cast Mag engines?

With the 502 MPIs, you don't have much weight change to the 509s? You have better trim results, that you can't replicate now with the new engines? Any other weight changes?

You closed cooling engine coolant drops to 150°f at 60mph? Or is the the raw water exit temps?

Cylinder bore wear skyrockets at cyl temps 150°f and below. It's pretty low in the 160°f + area.

try REV 4s. They're a great upgrade for lower X boats.

https://i.redd.it/pcfw6b7b15g21.jpg

:D
Just kidding Tom!

Tom,
Just for reference. My 30' TRS Scarab Panther ran 82.
454's 9.0:1
Dart (Valako) custom 345 Pro1's
Your Cam Motion cams, 235/241 (1.8/1.75 rockers) Isky solids on HR cam
Crane HI-6M 35° timing
120°F thermostat, 180 max oil
Stainless marine
approximately 575HP
Stainless marine TRS dry to the tips
25 Mirage slid hub 5800 RPM
Ran 71-73 with originaorl 420's
My TRS boat hates Bravo 1's, too much stern lift.

I'm running Merlin intakes (and heads) on custom built 468's in my 27/29 Fountain.. My next perf upgrade will be to rpl the intakes with some alum ones. I've never had to open these engs but prev owner did and said the intakes felt like they weighed 100 lbs each. Pretty sure I could lose well over 100 lbs with the swaps.

I'd start with what's easy....borrow some props.

years ago I had a 382 with big power. I usually ran a set of weird custom props being 15.625 diameter 28 Maximus (I tested them on a whim and the cruise speed was awesome). These would cruise 60@3,500 but only hit about 83mph at 5,150rpms. I also had a set of labbed 30P Bravos that cruised 53-54@3,500 however they would spin 5,700 hitting 87-88 mph......and yes, the motors were built for the rpms.

ironically the motors were Procharged when I bought it and ran a best of 98. However the negatives were such that I repowered N/A.

I'm with Team Saris on this one. Sounds like your motors are really healthy you're just hitting a water wall at 70mph. A nice work around is a prop designed to free up some of the drag at WOT.

You were running Mirage plus 25s, or non-cupped?

Stern lift is going to put the bow down a bit? Triming up the drive would counter the stern lift to try and air out the hull? HP loss there?

Lots of information to absorb and process.

First, a lot of weight has been taken out of the boat. I lost all of the heavy MPI stuff as well as the iron heads and so on. I did add the fridge back to the boat… I can use it, it works really well, and it made the cabin more solid if that makes sense. This was the first time ever running with it on the boat and we ran hard and quiet compared to before. It stays and isn’t that heavy. The crystal is sitting in my garage lol.

The boat still ran 70 maybe 71 with barely any trim so I think I could have been a little more aggressive with it. Like I said, the best with the MPIs was with the trim off the card to the point where you could feel the ass end start to wiggle. We were no where near there.

Rookie… it’s interesting that you mentioned 25P. I have a pair of solid hub 25P Mirages on the shelf that I could try to get the RPM up. I think 5500 is about the max I’ll run it though it honestly feels, based on seat of the pants peak torque rpm that it’s probably max power at 57-5900.

Will the TRS tolerate a Rev 4?

Raising the X dimension isn’t an option and if anything it’s probably worth a couple mile an hour for thousands worth of work. Bravos aren’t an option either… and I love the transmissions. Was a dream putting the boat into tight spaces this weekend. She did everything perfect with exception of wringing her out.

I believe I wrote 25 Mirage which do have cupping on them. In relation to a Mirage + they have less cupping.
I ran 25 Mirage's, 27 Mirage's, 25 Mirage's thinned and added cupping, 24 Bravo 1's, 26 Bravo 1's, 28 4 blade Spinelli's, 26 4 blade Spinelli's, 24 4 blade Spinelli round ears, and 27 Ballistic's
Yes, stern lift buries the bow a bit. You can only lift the bow so much before you blow the prop out. It would run wet and bow steer.

What props were these #'s with?

27P solid hub Mirages that came off the Bullet. I have no idea of what was done to them. They’re stamped with the owners information and some other numbers.

I’m assuming that if I went more aggressive on the trim I would have went well past those numbers. More basing it on last year’s experience but it was always hot and humid when I was out last season and I cut the season short.

As strong or stronger than a Bravo IMO.
I had 1 upper TRS failure in 20+ years on my Panther. I had 1 upper failure last year on my Bravo boat.

Not sure about how the Pather is setup but the 311 has a lot of rocker built into the hull. It wants to carry the bow and is very responsive to trim but will porpoise like a ***** unless the speed is high enough. The boat acted like this with the MPIs as well as with the new power.

Would a stern lifting prop be counter productive here?

More concerned about the right hand lower vs the upper.

I’ll be changing drive oil this weekend and hopefully won’t find any surprises. Rolling the props after Saturday’s run felt nice a smooth so I think both drives are still happy. I should probably buy a spare though.

Just for reference, I replaced my stock 7.4 non magnum if that matters intake and heads for aluminum stuff.
Factory intake weighed 46.4 lbs Edelbrock air gap 20.4 lbs.

so you put the fridge back in but took weight out by taking it out of the engines. so now you have shifted the center of gravity forward on the hull. now you have props that stern lift so you are running wetter than before. personally I would try 3 blades and see if it will set back on the stern and let it carry the nose better. old school straight bottom boats need to ride back on the transom and even a little change forward in CG can cause lots of issues.

For testing purposes, get about 150#s of sand tubes, lay them across the
engine hatch, wrap ratchet straps around the bunch and bottom of the hatch
and go out and run it.


This should replicate the center of gravity before the power change

“

How do I get more out of this thing?”

Kick it right in the nut sack and smash the throttles right through the fiberglass
:)

The fridge weighs really nothing. Less than 50 lbs and right in front of the helm. I also cleared a lot of other extra crap out of cabin during cleanup this spring so the weight is negligible.

I really do think it would have run faster with more trim. I was running the Mirages that are bow lifting -‘was just thinking of trying the 26P Bravos which I know are stern lifting.

That’s next on my list!!

https://cimg7.ibsrv.net/gimg/www.off...bd0c5178b9.jpg
:party-smiley-004:

That’ll get it done!

Hi Tom, what’s all this talk about the Formula? Thought you were a cig guy now. 😁

Hope all is well,
Chris

I’m a running boat guy is what I am. Plus, can’t get anyone to buy it so might as well enjoy the old girl!

Hope all is well with you, too, Chris.

Better intakes and exhaust, more compression, more cam, stroker, better X dimension. Nothing free besides weight reduction. Nothing cheap besides playing with props and flipping them, new intakes, or bigger cams.

Instead of screwing with raising a TRS most guys go for an SSM 5 swap. Much shorter and the transom cut out isn’t that different IIRC.

or this

https://www.offshoreonly.com/forums/swap-shop/374033-stellings-trs-bravo-extension-boxes.html

or Konrads

The engines are definitely capable. Good compression, cams are well matched to the heads, good intakes and carbs, good exhaust.

I’m at the props and balance stage at this point is my thinking.

Not sure I want to go into messing with the drives. I have her for sale and adding #5s or Konrad will never give me a return. I’d rather spend the money on my Bullet that will be a much faster and more capable boat (not that my 311 isn’t capable… my Bullet is just that much more).

The cool thing is that no matter what she’ll cruise all day at 55-60 and once you get her to 60, you can back off the rpm some and she’ll hold the speed. I’d just like to occasionally see the top end every once in a while.

The intakes and exhaust could be better. Merlin isn’t the best bbc intake and the elbow top isn’t a true full length header. Intakes are easy and cheap to swap. Exhaust not so much.