How to Improve your Gas Mileage

[David CVX-16]

While boating with Gregg last Saturday on the St. Croix, the motor was not idling well. Periodically, Gregg and I would compare our fuel gauge markings, and Gregg, with his 115 HP Mariner and getting much better gas mileage than my 115 HP Johnson. He was at more than 1/2 full while I was at 1/4 full. In fact, I ran out of gas and had to refill the 18 gal. tank with 5 gals I brought along in a portable gas can. Was getting 3 MPG and gas was dripping down the side of the motor.

Thought it was warped carb bowls, but it was a cracked fuel line to the upper carb.  Was about ready to take it in to a outboard motor mechanic.

One of the easier and inexpensive outboard motor fixes.

 

[Jason]

Glad it was a simple fix!

[V153]

Yeah, that might help ... Glad you caught it Dave! These things are thirsty enough without any help?

If I were you I'd replace all the fuel lines under the cowl. Including the lil choke/primer lines. I had one of those let go on the 90.

[Bayflite73]

Yikes! Glad you didn't have any other issues with fuel dripping down the side! Glad it turned out well!

[David CVX-16]

I also learned today that the motor runs better with the spark plug wires hooked up to the correct cylinders. Crossed up on one side. It ran, but would backfire. DAHHHHHHHHHHHHHH!

What is said on this site stays on this site.

[Hyperacme]

I thought it was just fuel draining out of carbs when he tilted motor up, BUT when Dave removed cover ... Motor was covered in fuel and running down the leg !
Easy fix !
But ya ... Think ya should replace all lines ...

Ya mean ya had a leaking fuel line and plug wires crossed, PLUS your son in the boat and you still beat me by 1/10 of a mph  ...
(50.7 mph to Dave's 50.8 mph)

Think I'll start lookin for a Johnson ... LOL

[V153]

What is said on this site stays on this site

Your secret is safe with us David ...

[Jerry]

Just the reason you don't use rubber lines on an inboard.

[David CVX-16]

Gregg, the spark plug wires were correct when we were boating last Saturday. I crossed them today when I took the spark plugs out to spray Merc Power Tune into the combustion chambers.

I have four different sets of spark plugs, and switched from NGK BUHW-2 to Champion L78V just to try them all and figure out what works best. Still have to try another set of NGK's. The NGK BUHW-2's worked well the Saturday before last with 52.3 MPH with two on board.

Keep trying different things until you find what works best.   

[V153]

Keep trying different things until you find what works best

Sounds a lil liberal when you phrase it like that David ..., but I do agree. If'n that's the case then you owe it to yourself to try some fine wire Irridiums @ 030. (They come gapped that way btw.) Trust me. The 90 liked em & so does the 140.

[David CVX-16]

Doug, NGK does not list the Iridiums as a spark plug for the 1985 115 HP Johnson motor. Here is what I found for my motor:

http://www.ngksparkplugs.com/part_finder/watercraft/results.asp?id=1171&type=reg

I also looked up 140 HP Johnsons, and did not see the Iridium listed for your motor. Do you just try it? How do you know the heat range is correct?


Year Engine Model Standard Plug V-Power Plug G-Power Plug Iridium Plug
 2005-2003   140 hp                 
 2002-1985   140 hp   LV4     n/a n/a n/a
 1984-1973   140 hp        n/a n/a n/a


Is this the plug for my motor?

http://www.ngksparkplugs.com/part_finder/watercraft/results.asp?id=1169&type=ir

[Rosscoe]

Yea I would think that would give you bad mileage David. Glad you had no other issue and could fix it yourself.

[David CVX-16]

The trip on the St. Croix was 45 miles and the boat used over 15 gallons of gas, less than 3 MPG. Factoring in the cost of premium gas at $4.14 per gallon and the cost of the Mercury Premium Plus oil, the cost per mile was $1.58.

Read where an Allison boat with a 90 HP Honda 4 cylinder could do 70 MPH, yet get over 8 miles per gallon at cruising speeds.
Maybe that is the line the husband uses to convince the wife to get an Allison.  Thats the answer! Only $40,000 up front to save a few bucks in gas on each boating trip.     

[wiliermdb]

Doug,

What plug are you running in your 90?

[V153]

I got the first batch from NAPA, pretty sure he just looked em up in their marine catalog? BR7HIX, B7HIX is the non-resistor version.

[David CVX-16]

Thanks Doug. Please mail those spark plugs and your SRX prop to me ASAP. LOL.

[V153]

Thanks Doug. Please mail those spark plugs and your SRX prop to me ASAP. LOL.

Ha! Hey just as soon's I recieve your pre-paid box Dave. Heh heh heh

That thing is a 24 now btw so it might be a lil tall for your boat, but mebbe not. This is a before pic: