Concept,

Full disclosure.... My experience is with the HP, which is not even Holley's most powerful unit, and I'm not doing the tuning myself, so I'm not intimately familiar myself. I have a guy that knows the Holley stuff, and several other ECM systems, inside and out that does that for me. I've watched him work with my ECM, and he's tried explaining most of it to me as he goes. We've talked about what it will do; the functionality that it has that I'm not even remotely tapping into. Pretty sure Holley allows you to build your own tables for whatever you need and assign functions and parameters to those tables. I'm not sure why anyone would want more control than the Holley allows. I can't, for the life of me, wrap my head around the notion that Holley "restricts" anything of any use in any way. Just my 2 cents....

Thanks. Brad.

Do any of these systems have the ability to hold RPM consistent in rough water? Essentially taking the human factor of throttling the boat out of the equation? I would think a computer would be able to react to the loading and unloading a lot faster than any human could.

302,

I would think it would have to be done with ignition advance unless you incorporated DTC. I wouldn’t think you’d want to deviate that much from an ideal advance. But I do know that the Holley system has capacity for DTC. The cool thing about that is that it eliminates the need for IAC, as it’s just incorporated into DTC.

Thanks. Brad.

Motec and Holley aren't even in the same universe.

If you got the budget and expertise to tune Motec I guess it`s a better choice. Most of the tables in Holley go unused, not sure why you`d need more stuff with Motec in a pleasure boat . Holley had anything and everything I ever needed and more.

Key Comparison for Boats

Holley ECUs (e.g., Terminator X / Terminator X Max, HP, Dominator) are popular in the marine world for their affordability, user-friendliness, and solid performance in many boat setups. MoTeC (particularly the M1 series) is a premium, high-end option favored in professional or extreme marine racing environments.

Here's a breakdown of the main differences based on user experiences, forums, and marine-specific discussions:

• Cost Holley: Much more affordable (e.g., Terminator X setups often in the $1,000–$3,000 range depending on kit and extras). MoTeC: Significantly more expensive (often several times the cost of Holley, with M1 series starting high and adding up quickly with custom configs/paddles/displays). Winner for most users: Holley — better value for street/performance boats or budget-conscious builds.
• Ease of Use and Tuning Holley: Very user-friendly software (consistent across models like Terminator X, HP, Dominator), self-learning capabilities in many cases, large community support, tons of tutorials/videos, and easier/cheaper tuning (local tuners widely available). Many describe it as a "no-brainer" for setup. MoTeC: Extremely powerful and customizable, but steeper learning curve, more complex software, and typically requires a highly experienced tuner (often more expensive). It's built for precise, advanced control. Winner: Holley for most boat owners; MoTeC if you need ultimate flexibility and have pro support.
• Features and Capabilities Both handle fuel/ignition control, data logging, boost (if applicable), etc. Holley: Strong in basics + good expandability (e.g., inputs/outputs on Dominator), integrates well with dashes, reliable for marine EFI conversions (some marine-certified options). Popular for LS swaps or carb-to-EFI conversions in boats. MoTeC: Superior in advanced features like traction control, power management, highly detailed modeling (e.g., injector characterization), integration with sophisticated dashes/gauges (e.g., Smartcraft compatibility in some marine setups), and extreme reliability in harsh conditions. Often chosen for high-end offshore racing or Mercury Racing mods (e.g., plug-and-play replacements for factory ECUs). Winner: MoTeC for pro-level racing; Holley sufficient for 90% of performance boat applications.
• Marine Suitability and Reliability Both can work in boats, but marine environments (humidity, salt, vibration, water exposure) demand sealed/potted units. Holley: Has marine-certified options and is commonly used/recommended for boats (e.g., airboats, performance V8s). Some users report solid reliability, though occasional failures noted in harsh conditions. MoTeC: Built with high-end durability in mind; often praised in demanding marine racing (e.g., one-for-one swaps for Mercury outboards). Seen as more "transparent" and robust for extreme use. Note: Always prioritize marine-rated components (sealed harnesses, waterproofing) regardless of brand.
• Support and Availability Holley: Widespread support in the US (especially performance/boat communities), easy parts/accessories. MoTeC: Excellent but more specialized (dealers/tuners often in racing circles); less "plug-and-play" for casual users.

Bottom Line

• Choose Holley if you're building/upgrading a recreational or mid-level performance boat, want easier tuning, lower cost, and good community resources. It's a go-to for many in boat forums (e.g., River Daves Place, Holley marine threads) and handles most needs without overkill.
• Choose MoTeC if you're in serious offshore racing, high-horsepower mods (e.g., Mercury 300R/450R upgrades), or need the absolute best precision, advanced controls, and durability — it's often considered "the best" in pro marine circles, but at a premium price.

Ive thought about this in the past
 

but decided my throttle arm is easier to tune and set up lol

Understanding the Problem

In rough water, when a boat's propellers (props) exit the water, the engine experiences a sudden loss of load, causing RPMs to spike rapidly (over-revving). Upon re-entry, the sudden torque load can stress the drivetrain, engine, and props. Manually throttling back helps, but an automated ECU solution can detect this unload condition and intervene by limiting RPM, retarding timing, cutting spark/fuel, or modulating throttle (if using drive-by-wire, DBW). Your idea of a driveshaft (or prop shaft) speed sensor is spot-on—it can detect rapid RPM acceleration (rate of change, or dRPM/dt) or mismatches between engine RPM and shaft speed, triggering protection.

Both Holley and MoTeC ECUs can handle this, but MoTeC's advanced programmability makes it more flexible for custom marine strategies. Holley is more user-friendly and affordable for basic setups. Neither has a "plug-and-play" prop unload feature, but you can configure one using sensors, inputs/outputs (I/O), and logic. Always consult a professional tuner, as marine environments require waterproofing and robust wiring.

General Setup Approach

1. Sensors Needed:
   • Driveshaft/Prop Shaft Speed Sensor: Hall-effect or magnetic pickup on the driveshaft or prop shaft (e.g., from Cherry Sensors or Auto Meter). This measures shaft RPM. Compare it to engine RPM—if shaft RPM lags or accelerates abnormally fast, it indicates unload.
   • Optional: Accelerometer (for boat pitch/motion), hull speed sensor (GPS or pitot), or wheel speed equivalent (adapted for marine).
   • Wire to an ECU input (digital or analog, depending on sensor).
2. Detection Logic:
   • Rate of RPM Change (dRPM/dt): Monitor engine or shaft RPM acceleration. If it exceeds a threshold (e.g., >500 RPM/sec), activate protection.
   • Load Mismatch: If engine RPM spikes while shaft speed drops (prop in air), intervene.
   • Intervention: Soft RPM limiter (retard timing, cut spark/fuel progressively), throttle reduction (DBW), or torque reduction.
3. Safety Notes: Test on calm water first. Use data logging to refine thresholds. Ensure marine-rated components (IP67+ sealing).

Holley ECU Setup (e.g., Terminator X Max, HP, or Dominator)

Holley excels in affordability and ease but lacks built-in RPM rate-of-change limiting. You can approximate it with rev limiters, advanced I/O, and custom logic. For boats, use marine-certified kits (e.g., with sealed harnesses).

• Basic Rev Limiter for Over-Rev:
  • In Holley EFI software (V6+), go to "System Parameters > Rev Limiters".
  • Set a "Soft" Main Over-Rev Limiter (e.g., low side 6050 RPM, high side 6100 RPM for a 5800 RPM redline boat). This pulls fuel/spark progressively as RPM approaches the limit.
  • For waves: Widen the soft window (e.g., low 5500, high 6100) to give more time for intervention during rapid spikes. Users in boat forums report this reduces stress on re-entry.
  • Options: Fuel-only cut (hard), spark-only (softer), or combo. Add coolant/air temp offsets for safety.
• Advanced Setup with Driveshaft Sensor for Rate Detection:
  • Wire shaft sensor to a digital input (e.g., "Speed Input" on Dominator).
  • Use "Advanced Tables" (1D/2D) under "Toolbox > Advanced" to create custom logic:
    • Map shaft speed vs. engine RPM. If mismatch > threshold (e.g., engine RPM > shaft RPM * gear ratio + 10%), activate an output.
    • For rate: Holley doesn't have direct dRPM/dt, but use "Slew Rate" (rate limiting) on outputs like ignition retard or throttle (DBW). E.g., limit RPM rise to 300 RPM/sec by retarding timing progressively.
  • Integrate with MSD (Holley-owned): MSD 7531 boxes have "Slew Rate Limiter" for RPM control (originally for traction). Set slew to limit acceleration (e.g., 200 RPM/0.1 sec). Jet boat users use this to prevent impeller cavitation (similar to prop unload).
  • DBW Throttle Control: If equipped, set "TPS Boost Modulation" or safety setups to close throttle on high acceleration (under "Boost" or "Safety").
  • Inputs/Outputs: Assign a switch or sensor-triggered "Rev Limiter #1/#2" (e.g., launch or burnout mode) to drop RPM temporarily. Use "Pin Map" to wire sensor as trigger.
• Pros for Boats: Affordable ($1k-$3k), large community (e.g., PerformanceBoats.com threads on jet boat EFI). Works well for V8 inboards/outboards.
• Cons: Less custom than MoTeC; may need external modules (e.g., MSD) for true slew rate.
• Example from Users: In supercharged boat setups, widen soft limiter for wave-induced spikes; add timed retard (e.g., 5° pull for 0.5 sec on detection).

MoTeC ECU Setup (e.g., M1 Series or MCM112 Marine Kit)

MoTeC is premium and highly customizable, ideal for pro marine racing (e.g., Mercury outboards). The MCM112 plug-in kit for Mercury 200-500R engines supports prop speed sensors natively, making it perfect for unload detection. Use M1 Tune software for configuration.

• Built-in RPM Limiter:
  • Under "General > RPM Limit", set "Engine Speed Limit Maximum" (e.g., 6200 RPM). Adjust "RPM Limit Type" (1-3: ignition cut, fuel cut, or combo) and "Ctrl Range" for softness.
  • "RPM Rise Rate": Set rate of change for limiter activation (e.g., limit rise to 400 RPM/sec). This directly addresses rapid spikes— if dRPM/dt > threshold, it cuts power smoothly to prevent over-rev.
• Advanced Setup with Driveshaft/Prop Sensor:
  • MCM112 Features: Native "Propeller Speed Sensor" input (measures prop RPM). Also supports multi-engine sync, drive trim, stern leg position, and moving prop alert (warns if prop spins while idle).
  • In M1 software:
    • Wire driveshaft sensor to a wheel/drive speed input (e.g., "Wheel Speed Rear" channel, adaptable for prop).
    • Create math channels for dRPM/dt: Monitor engine RPM acceleration or compare prop RPM to engine RPM (accounting for gear ratio). If prop RPM drops (unload) while engine spikes, trigger limiter.
    • "Engine Speed Over-Rev Protection": From GPRP package (adaptable to marine)—uses speed sensors to calculate and prevent excessive RPM. Replace "wheel speed" with prop/hull speed (e.g., via GPS input) to match engine RPM to boat speed on re-entry.
    • Custom Logic: Use "Limiters" worksheet for overheating/low oil protection, extend to unload. Activate torque reduction, throttle blipping (DBW), or ignition retard.
    • Downshift/Shift Protection: Though no gears in boats, adapt "Gear Shift Down Engine Speed" table for virtual "modes" (e.g., lock out high throttle if over threshold).
  • Marine-Specific: Ruggedized (polyurethane-potted) for water/dirt. Integrates with Mercury dashes, CAN bus for multi-engine boats. Knock control included for stress detection.
• Pros for Boats: Superior for offshore (e.g., 450R/500R mods). Prop sensor + rate control prevents damage. Level 2 logging for wave data analysis.
• Cons: Steeper learning curve, higher cost ($3k+), needs certified tuner.
• Example from Users: Mercury Racing integrations use MCM112 for precise control; forums note easy tuning once setup, with back-end math handling VE/fuel precisely.

Recommendation

• Holley: Great for DIY or budget builds. Start with soft limiter adjustments and add MSD slew for rate control. Ideal if your boat is recreational.
• MoTeC: Better for high-performance/offshore where custom rate-based protection shines. Use MCM112 if Mercury-based; otherwise M130/M150 marine-grade.

I'll second that. Motec punches WAY above its price point. The beauty of Motec is the hardware quality at the price point and the closed loop accuracy and speed.

Motec is plug and play with the DTS. Plug it in and go. Big gains on a stock engine with a pretty mild tuneup.

MoTecs cost the same or less then a 2nd set of propellers. You will never recognize a better gain for the money, their support is incredible, and its up to you how far you choose to push the envelope "knowing that everything has a breaking point".

Joe

On the non-supercharged outboards, how are they getting more power out of them? Are these newer 4-strokes just that conservatively tuned from the factory?

Also, on the newer Merc V8's, how much can the rev limiter be raised without sacrificing reliability?