Running at less than WOT

[granite]

I understand it's important to have your motor propped so that it reaches the correct rpm at WOT. I have a 60 hp 1994 Mariner on a 17 foot Monark aluminum boat, runs 5500 rpm at WOT, which appears to be right on target. Is it ok to reduce the throttle while cruising, back to about 3500-4000 rpm to save gas and wear/tear on motor, or would this be harder on the motor? The boat runs just about as fast at this rpm (or fast enough, anyway) and probably eats a lot less gas, but I don't want to do anything to hurt the motor. Thanks.

[Lancer6]

Originally Posted by granite

I understand it's important to have your motor propped so that it reaches the correct rpm at WOT. I have a 60 hp 1994 Mariner on a 17 foot Monark aluminum boat, runs 5500 rpm at WOT, which appears to be right on target. Is it ok to reduce the throttle while cruising, back to about 3500-4000 rpm to save gas and wear/tear on motor, or would this be harder on the motor? The boat runs just about as fast at this rpm (or fast enough, anyway) and probably eats a lot less gas, but I don't want to do anything to hurt the motor. Thanks.

By all means, run at lower RPM whenever practical. You should be able to find a speed, once on plane (assuming the 60HP will actually plane the boat,) that will cause you to achieve better fuel economy AND less wear and tear on the engine. It stands to reason that lower RPMS will result in longer engine life, all else being equal.
Usually, somewhere between 2/3 and 3/4 throttle will be the "Sweet Spot".
Since you're running a 60HP motor I recommend you "lighten ship" so much as possible. Here are some tips...

Carry only enough fuel (with a safety margin factored in, of course,) as you might expect to burn on any given trip. Fuel is heavy!

Remove so much tackle as you can, keeping only what you might expect to use during a given outing.

If you don't usually drop anchor to fish, remove the anchor from the boat, assuming you carry one. You might carry one, better yet...two brush clips in the event you might wish to "anchor" to some brush to eat, make repairs, re-rig tackle, or fish a likely spot for while. This saves trollmotor wear, tear, and batteries too.

Ask your partners/guests to downsize their tackle as well.

Perhaps carry a smaller cooler than usual. Instead of ice, purchase freeze packs and use those. They last well and you won't reach for your peanut butter and anchovy sammich only to find it has become soup.

Experiment with weight distribution in the boat. You're looking for a setup that most easily allows the boat to plane at a reduced RPM. Adjust the balance for when you are alone, if that's the case, and for when you have a second fisherman on board.

Do some research on prop pitch and diameter. Although there may not be a wide array of props available for a 60HP there may be an alternative which may better suit your needs.

If you have trim and tilt, learn to use trim to optimize performance at lower RPM AND gain RPM with less strain and fuel use as well when more speed is desired.

Others here will probably chime in soon with additional suggestions, hopefully some with experience with rigs similar to yours.

Good luck! Be safe...Kill switch and PFD!

Lancer6

[zooker]

actually on the 60 horse you can back it down to about 4000 to 4800 and get better milage. you drop it down much more than 4k and you start to "dig in" or have more weted surface....

me i punch it get it all trimmed right and back it off to about 4500 and cruise..

zooker

[1FASTLASER]

You are right on the track granite......and might I add did your homework. The reason for proping a boat to reach its max rpms at a given WOT or optimizing as I call it is the reason you can back off the throttle after getting her on pad and increasing the fuel mileage and the wear and tear on the mtor. The RIGHT prop and engine height as well as the RIGHT load being properly placed in the boat not only increases the mileage performance also is a BIG saftey factor.

[granite]

Thanks for all the info. I must admit I carry more stuff in the boat than I "need" to, but the convenience vs. the cost (in speed, holeshot etc) is worth it. I fish in northern NH where on a 3,500 acre reservoir or 8 mile stretch of the CT river I might see two other boats, so speed is not really a priority. I think the fiberglass guys might forget how easy it is to push an aluminum boat. The 60 horse has no problem getting on plane ( it does have a hydrofoil on the motor) and cruises in the upper 30's with me and my (admittedly hefty) gear load. I'm sure I'll have more questions, as there's nobody at the ramp to ask!

[Rebbasser]

I must admit I carry more stuff in the boat than I "need" to,

As do we all

I agree with the advice already given-if speed isn't all that critical back her down and enjoy the ride.

[boater]

Lasers right on you did your homework and have your rig proped right.that WOT # is just to get the right prop. you don't ever have to run WOT I never do...wait I mean seldom do....Wait I mean sometimes I don't ...well when momma's in the boat anyway.

[NWOhioBear]

Another trick my dad taught me is when loading the gear make sure it's all placed in the back 1/3rd of the boat. This allows the boat to hit plane much easier. Saves a ton on gas if you can get it up and then just cruise. Just play around with your boat and you'll find what Lancer said the "sweet spot".

[MississippiBoy]

Negative, Ghost Rider. The more weight you have in the back of the boat, the greater tendency for the nose to ride higher, increasing the angle the hull meets the water. This makes it more difficult to get the boat up on plane.
In my little 14' boat, if there's two of us in the back, the 40 hp Yamaha struggles to get us up. If I put the passenger in the front seat, it's much much easier.