Full Throttle: Long Trips

[Robert Sands]

Hello everyone,

I wanted to start a new thread on this particular topic as an attachment from a Scarab jet boat towing thread made me ask a question and I couldn't find the answer in existing threads.

In the attached document it states that during the break-in period (first 10hrs) we should keep the throttle at roughly 3/4. I'm well past that period and use full throttle on my 195 HOI routinely, but I'm wondering if keeping it pinned for long trips is acceptable? Sometimes we make the trip from marina to marina on a nice day, with smooth water we could travel at full throttle for quite a long while. Provided the engine seems to be operating normally and I'm keeping an eye on engine temp, should I be mindful of this or plan in breaks for the engine? Just wondering, thanks a lot.

 

[McMark]

I've always used the 75% of max RPM rule of thumb for extended cruising.

 

[Shuck Water]

Think of it like you're flying an airplane. Push the throttles all the way forward initially to get up to speed and then back off to a "cruising speed". My rule of thumb for WOT is no more than 20 minutes.

 

[DUSTOFF]

I keep an efficiency chart mounted near the throttles so I use that to cruise at max range RPM unless I want to crank it up and have fun.

7500 RPM and ~31 MPH is max range for the AR230

 

[Seadeals]

I know the question is initially specific to Scarabs; but this is an interesting question that got me thinking about the importance of considering your specific engines before following a general rule of thumb.

The version of the MR1 in my boat (the early 210 series boats ) is rated at 110 hp and they typically max between 8000 - 8400.

The 140hp version typically turns 9800-10,000 rpm.

the 160hp version turns 10,000-10,300.

This makes me struggle to find a legitimate concern other than fuel mpg running the same pistons/rings/cylinders at WOT indefinitely when the other versions are +2000 rpm at WOT. 75% for my engines would have me around 6,000 RPM. That would definitely make for an "extended cruise" as she drops off plane.

Naturally fuel burn rates (mpg), schedule, conditions and passenger comfort should play a part.

 

[bronze_10]

I know the question is initially specific to Scarabs; but this is an interesting question that got me thinking about the importance of considering your specific engines before following a general rule of thumb.

The version of the MR1 in my boat (the early 210 series boats ) is rated at 110 hp and they typically max between 8000 - 8400.

The 140hp version typically turns 9800-10,000 rpm.

the 160hp version turns 10,000-10,300.

This makes me struggle to find a legitimate concern other than fuel mpg running the same pistons/rings/cylinders at WOT indefinitely when the other versions are +2000 rpm at WOT. 75% for my engines would have me around 6,000 RPM. That would definitely make for an "extended cruise" as she drops off plane.

Naturally fuel burn rates (mpg), schedule, conditions and passenger comfort should play a part.

My boat doesnt really start getting any spring in her step till about 6500 rpm.... 7k will normally hold plane... 7200 and up and she will stay on plane easy but she's not going very fast..

 

[jwells]

Does anyone know how this applies to Yamaha. This is something I always wonder about I like to go when it's smooth out and on the Ohio River it can be a long ride. I've always wandered how hard it is on these engines

 

[bronze_10]

I have read that these motors in motorcycles spin up to 15 thousand rpm... the mr1 in my 2008 turns 10200.. not sure about the newer boats.... but if that is the case my engines are not working near their manufactured max.... but on a motor cycle you wouldn't wind it up to 15K and hold it like happens on boating.. different applications I suppose.

 

[Speedling]

Cooling capacity increases with rpm as well. Full throttle burns a lot more gas, vut shouldn't be too horrible for it. Hard on bearings though so be on top of those oil changes for sure! I wouldn't recommend going through a full tank at wot on any engine. They are probably tested by manufacturer like that but no way is it good for it.