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1997 Merc 25 hp EL

mike_i

New member
"Does this engine have a rev limiter? I am using it on a small skiff, at WOT and proper trim I am clocking 30mph on gps. I am concerned about over revving as I don't have a tach."
 
"Hi Mike,

Firstly, welcome


"Hi Mike,

Firstly, welcome to the most informative boating forum in the world. [no, I'm NOT on the payroll. Yet.]

Assuming the engine is stock, they cannot be over-revved when cruising. Unless the prop falls off or when there is no load on the crank. Hence, when running the engine on muffs, do not run WOT when there is no load. This could damage the unit.

So, as it stands, if you're concerned as to the high RPM's, go for a coarser pitched prop if you hitting the high end of the rev band too easily. You'd want to see 5k+ revs when cruising. Back off the gas slightly when on the plane, no reason to hoof it WOT and not feel the difference while burning $$$ in gas bills.

What is the pitch of the current prop? OEM or aftermarket prop? Maybe add another inch or so in pitch to drop the revs.

Keep us posted!"
 
"Hello Mike - no, no over rev

"Hello Mike - no, no over rev protection for this particular model.

However, as Benjamin notes, under normal operating conditions it would be nearly impossible to over rev it since it's wide open throttle range is 5000-6000 rpms.

So even if you were underpitched a bit, it would be quite difficult to wander out of that 1000 rpm band.

If you are concerned you can pick up a product called "Tiny Tach" - sells for about 35 bucks. The lead wraps around the top spark plug wire and you get a digital readout of the rpms - and it can be mounted just about anywhere on the boat if you want to make it a permanent install..."
 
"Thanks guys. I had a 13 pitc

"Thanks guys. I had a 13 pitch prop on it when it made 30mph. It sounded like it's legs were stretched pretty well at WOT. I have since put a 14 pitch prop on, but the weather hasn't let me get a good run on it yet.
I have also gotten a DVOM with an inductive tach lead to try as well."
 
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