Acceptable RPM range for outboard ranger tugs

[JoelandDebbie]

After cruising for almost two years now on our R-23 I have found that I run the motor a little over 5000 rpm pretty much all the time (unless puttering around for a sunset cruise etc.). Seems like I don't get up on plane until hitting 4800 or so.

The boat runs fine and feels great - actually I quite enjoy it! But, I have found when chatting with other boaters who have outboards who are not Ranger tug owners, they rarely ever run their motors at such a high RPM (at least for very long). So my question to you is... what is an acceptable RPM range that an outboard motor can run safely and reliably for long distances? I have the Suzuki DF200A motor.

I'd like to hear what others experience and how they run their motor.

Thanks!

Joel

 

[az9133bm]

Likely, we don't have much of a choice but to run these engines close to WOT on the R-23. Fully loaded, on a hot day, on a lake with an elevation above 2000', our R-23 will fall off plane much below 5000 RPM. However, our opinion is that our Yamaha F200 remains smooth, relatively quiet, and economical when operating near the higher end of its operating RPM.

The right propeller makes a big difference in the RPM/Performance equation. At Lake Powell, for example, we could not plane with the factory prop (14.5 x 15) until we burned off half our fuel, food and water. We installed the same three blade 14.5 Yamaha Reliance Series but at 13 pitch and now operating RPMs are mostly the same but the biggest benefit is being able to plane our fully loaded R-23 on Lake Powell without using any tab; the boat seems more responsive all around.

5200 RPM = 27 MPH @2.1 MPG

 

[baz]

II'm told that running the OB motors at close to WOT is AOK all day long. These OB's are almost like racing engines and they like the high RPMs and aren't that happy at low RPMs even though they run just fine at lower RPMs.

When you take the OBs in for service they usually will plug in their computer to extract the engine's logging data, and if they see the engine has been run at low RPMs for extended times vs. running at high RPMs for extended time they get really, really sad. 😱 :roll:

 

[BB marine]

The newer 4 stroke outboards are bullet prove. There are more issues with bolt-ons.( electronics, alternators, electrical connections, injectors and fuel pumps ,the failures are not due to rpm) These bolt-on failures are not frequent but are more common then low hour ,high rpm operating power head failures. Running the engine at 5000 rpm all day long is ok, especially on a boat that needs to run at that rpm to be on plane. The most important component of protecting the longevity of the engine is proper propping. There are two ways of propping the boat (1) A reputable dealer during the commissioning process, before delivery will test run the engine/boat combination with standard equipment ,fuel and water tanks full. The technician will open the engine up to confirm full WOT at Max Rpm to +200 above Max WOT RPM.( 200hp Yamaha, 2.8L engine 5000 to 6000 rpm) A good Max rpm for the new boat loaded light would be 6000rpm to 6200rpm)
The reason for this is when the owner moves on board with all their gear and equipment the engine will be run with more load. (2) The better way but seldom done. A fully loaded boat should still allow the engine to turn to the Max RPM or within 200rpm of max. Like most boaters adding more gear than probably needed.If 5800 RPM WOT is not achievable with a fully loaded boat it is time to re-prop, drop pitch. Prop the boat the way you equip it. Always shoot for the Max RPM recommendation. If the boat is propped correctly "rule of thumb" 80% of WOT all day long. 6000 RPM WOT 80%= 4800rpm or 5800 rpm 4640 if you need 5000 to plane then the added rpm is better than the load on the engine trying to plane. If you get on plane at 5000rpm back it down and find the sweet spot that the boat will maintain plane with reduced rpm putting the engine at 80%.If this isn't achievable run it to the lowest Rpm that still Maintains plane.
https://www.rangertugs.com/Userfiles/Do ... 14_OWA.pdf
(Look at WOT Max and best RPM for speed and economy in the pdf) You are not going to see these numbers on a loaded boat. But you should still prop the boat to see the RPM numbers posted to protect the longevity of the engine.

There is nothing wrong with using trim tabs to maintain a proper plane. With having the advantage of the extended engine bracket ( engine mounted higher and offset from the transom). Adjusting trim tabs slightly down in conjunction with engine trim position slightly up helps keep the boat on plane and gives the hull lift to gain better performance at slightly lower rpm.

 

[az9133bm]

Brian,
We're glad you have confirmed our experiences. We agree that the right prop is key to enjoying the boat. We can achieve WOT with the 13" pitch despite loading, temperature, and altitude. Maximum speed for us at WOT with the 13" is a surprising 38 MPH (calm, cool, low altitude, and lightly loaded).

Tabs seem very responsive on the R-23; a little can go a long way. Use of tabs seems to be an art-form and varies so much with conditions. We are pleased to have this feature and enjoy experimenting with various applications of tab in various conditions. We look forward to trying your down-tab/up-trim technique.

As it relates to tabs and planing we've discovered a bit of down tabs right at the moment she's about to plane really helps quicken her last step. We'll deploy down tabs sooner if faced with headwinds and seas or when we're running heavy.

The critical weight factor in our boat is the amount of liquid we have onboard: 80 gallons of fuel and 22 gallons of water in a 8'6"x 23' LWL boat is a substantial load that you can't help but notice how it affects performance.

George

 

[Cutwater28GG]

the other solution is to remove the weight from the boat. I think we could all do with a spring cleaning and remove gear off these light weight boats...