How many RPM's?

[G3Ben]

Hi,
I was wondering how many RPM's below the recommended RPM range becomes bad for the motor? I know when you are significantly lower than the recommended RPM range at WOT extra stress is put on the motor from the load. So what number of RPMs below the recommended RPM range can you go without stressing the motor? Thanks.
-Ben

[SS 201]

At 5250 where the HP and torque meet.

[194265]

I agree with SS 201 on engines that are rated @ 6000 RPM. If your engine is rated at 5500 RPM or lower, I would say no more than a 10 % drop.

[G3Ben]

Thank you very much!

[Mark75H]

I disagree. It varies dramatically from motor to motor.

Older inline 6 Mercs for example, can be damaged by loads in the 5,500 rpm range, even though they were rated for 5,200 to 5,800.

[seaward]

I disagree. It varies dramatically from motor to motor.

Older inline 6 Mercs for example, can be damaged by loads in the 5,500 rpm range, even though they were rated for 5,200 to 5,800.

I started 2 stroke life in 1972 , at that time most inline 6's wer'e around 5800. i advised my customers to prop for that with a load. i could be wrong.
Hal

[Mark75H]

I just double checked ... the original low end was 4,800 until 1977. Some were top end 5,300 others 5,800, the XS 6,000

[Powerabout]

F1 car guys seem to keep over 14000, I guess they know what ther'e doing
dont see them at 5250rpm

[seaward]

I just double checked ... the original low end was 4,800 until 1977. Some were top end 5,300 others 5,800, the XS 6,000

When i was in my 20's I ran a 6 inline xs on a Carlson Contender. 26 cleaver, 7500 RPM ' I really thought I was cooking. These days seems like the v6 is the only way to go. Couldn't turn the boat though. I finally put a skeg in to help.

[seaward]

F1 car guys seem to keep over 14000, I guess they know what ther'e doing

F1 boats in the US run limiters to keep speeds down.