Conserve fuel using one of twin outboards

H

halibut taco

New member
I plan to take a long trip next week and hope to stretch my fuel supply by using one of my twin 90's to push the boat at displacement speed while exploring some bays along the way. If I shut one engine down and chug along at 5-7 mph will I be doing any harm to the second engine by leaving it lowered in the water? Do I need to tilt it up?
Also, will fuel savings even occur since the single will need a higher rpm than two together? Thanks for your thoughts on this.
 
We do this often with the TC. The fuel mileage jumps from 2 MPG to 4-5 MPG on a single Honda 150. Your mileage should be better.

With one engine raised, the steering is hard and on our boat, some of the cavitation plate and Permatrim are still in the water. We just leave the inactive motor down and in neutral. When the hour meter clicks over one hour, we switch to the other motor. No ill effects on the inactive motor.
 
You will probably get somewhat better mileage with one engine at displacement speeds. Leaving the non-running engine down will do no harm - unless you run into a rock or submerged log! Better to lose one prop or lower unit than two. Especially in shallower areas, I tilt the non-running engine all the way up. I would do that if it doesn't interfere with your steering somehow. (It's not a problem on my boat.) I think having only one engine down also decreases drag and probably further increases your MPG.
 
We often run with one engine up. We keep it tilted up to reduce drag and just in case we were to hit something in the water, the one tilted up would be OK.

Robert
Enroute to Calgary via View MH - missing our CD22 until next year
 
I am a Gunkholer at heart, it is by far my most favorite pastime on the water, just putt-putt-putting along at idle speed exploring skinny water. With our twins I raise one so the skeg is just clearing the surface and the other is at regular depth. With a remote in my hand and an extended emergency kill cord attached to my wrist I'll can sit up on the bow for hours. Spent many a happy time exploring the bays and coves around Sitka, Puget Sound and various lakes.

Can't speak to the mileage part but this has had no ill effect on either motor and never dinged a prop. Does seem to have a major positive impact on sanity though, very quiet and provides an amazing ability to get almost within touching distance of most wildlife.

I also tend to kill one motor when exploring near shore on lakes with waterfront homes as I prefer not to disturb the homeowners with noise, it also allows the chance to hear all the waterfowl, frogs and such. Our boat has hydraulic steering so there has not been a noticable impact on turning ability. If you are really concerned about the impact to the one motor, I'd suggest monitoring the water temp coming out of the one running motor's pee hole versus the temp when running both motors.

Hope you have a great trip!
 
Thanks for the replies. My cooler rack keeps me from raising one motor easily which is why I asked. Doesn't sound like it will be a problem to leave it lowered.
 
If you want the best mileage and must leave the motor down, you can decrease drag by removing the prop---probably not worth doing.

Put equal number of hours on both engines. No harm to leave the engine down.
 
halibut taco":21allkt9 said:
Thanks for the replies. My cooler rack keeps me from raising one motor easily which is why I asked. Doesn't sound like it will be a problem to leave it lowered.
Click to expand...

Just a note for those who are thinking of designing their own cooler rack:

I considered the need to raise the motor when I designed mine, and with a 2005 90 hp Yamaha 4S, moving the rack design forward about 10 inches (as I remember, YMMV), allowed me to raise the motor with the rack and cooler in place. The extra 10 inches forward didn't adversely interfere in the use of the cockpit too much.

IM003308.jpg
Click on photo for more!

Joe. :teeth :thup
 
Back
Top