Exceeding max RPM question

[Mucho Gusto]

Hey guys- lots of talk about prop pitch and RPM's on here, so I wanted to share my experience and get your insights...

Engine is a Verado 175 and it has a 15 pitch Enertia prop. At WOT, the engine operates within its max range of 5800-6400 when trimmed down. However, as I raise the tilt, the rpm's can increase up to the 6800-6900 range.

On the performance reports on the Mercury website, this engine was tested with this prop so I'm pretty confident that this is the right combination.

when running wot, should I simply keep trimmed down as much as possible, not worry about it, or consider a prop change?

Thanks for any input!

[ToonGuy]

Way to many variables to say "it was tested with this prop". Every boat and combo is different. When you have enough power, trimming the motor up will raise the bow of the toon, getting more of the tubes on top of the water and thus less resistance results in higher speed and RPMs. It's my personal belief that your boat should be set up to not exceed it's maximum RPM range EVER. So while swapping the prop may result in lower performance when you are fully loaded, you won't run the risk of hurting the motor if/when you decide to push it a little hard another time. If it were my boat, I'd swap props.

[BoatCop]

Any engine/prop combo will exceed recommended RPM if the prop comes out of the water. As you raise the engine the prop is moving behind the center toon or engine pod and will ventilate. Keep raising it and the prop will come out (or close to out) of the water, exceeding the engine's designed RPM and/or the rev limiter.

If the engine RPM is within the recommended range at normal cruising, then that's about as good as you can hope for. Different props might get you a MPH or 2 higher, but as you increase top end speed, you sacrifice low end performance.

[RcgTexas]

the rpm's can increase up to the 6800-6900 range.

I am surprised that the rev limiter let it go that high. If you are not cavitating, you need more prop!

[Bamaman]

Sounds as if you really needed a 17 pitch prop. Don't know if changing the prop would be worth it, however.

My next door neighbor has the same Harris with a Verado 150, and it's got an Enertia 14 pitch.

[Mucho Gusto]

the rpm's can increase up to the 6800-6900 range.

I am surprised that the rev limiter let it go that high. If you are not cavitating, you need more prop!

I'm surprised a limiter does kick in as well. Makes me wonder if the tach is correct?? I'm going to email the dealer and see what they suggest.

Thanks to all for your feedback!

[DWRAT]

Your tach has to be reading high like mine was.
Get a Mercury smart craft gauge before you go changing anything if you don't already have one.

[Bamaman]

The Verados redline a little higher than other outboards--maybe 6400 rpm's. And I would have figured the rev limiter would have kicked in before the engine hurt itself.

And I was also thinking the tachometer might be reading an inaccurate number.

Your dealer's shop could put a tach on your engine to tell you the accuracy of your boat's tach. It would be important that you know your rpms before re-propping your boat.

[Littlehoe]

I have had my motor for 3 years and have never hit a rev limiter or been able to get it to perform how it was supposed too. It's been in the shop numerous times, its even on its second boat in those 3 years. The guys from the dealership have come with me to the lake to try to figure it out and no luck, we have tried 8-9 different props. Finally I had just settled with the best performance we could get.....Until this winter when I was doing more internet searching and found that the tach is adjustable with a little dial in the back. After more reading and checking online and in the boat this whole time my tach has been set wrong and the dealership never figured it out. So before you trust what the dealer says, start checking for yourself, check what your tach is set at, and what it should be set at.

[Stinger 88]

I experienced a similar situation last year after purchasing my new triton. Ultimately found that the setting on the back of the tach was not in the correct position for my Mercury motor. Problem was, the setting picture in the manual for the tach was opposite of what is on the tach itself (backwards). The Manual showed 1-6 positions left to right, tach was actually 1-6 right to left. Once I positioned the set screw in the correct position the tach was fine.

[Mucho Gusto]

Thank you all for your feedback! The head mechanic at the dealership told me the rev limiter would've kicked in if the real rpm's were that high. Said the tach is probably justing running high and that I'd be much happier with the 15 pitch than something higher, especially with more people on board.

He didn't mention anything about the different settings on the back of the tach....I'll have to check that out when I get the boat from storage next weekend.

For the interim, it sounds like I'll be able to keep a little money in my pocket!!