Noticed yesterday that my mileage range has dropped considerably on my XR4. I made about a total run of about 15 miles yesterday and ran out one of my half tanks in just that run alone. Are my carbs out of adjustment causing it to use more fuel now? I was thinking that at about 40 mph steady speed, I was getting about 25-30 miles out of one tank. I know most people are running newer engines, but I really don't have the funds to make the purchase and it is still running. Thanks.
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Mercury Black Max 150 xr4 gas mileage problem?
- Thread starter jonathanr
- Start date
My understanding is that if you can get 4 mpg or above on anything on the water that's great! My old Johnson 200 Venom Carb was maybe 2 mpg! I remember just a few years back when Mercury had Roland Martin doing endorsement TV and print ads saying the he could run 200 miles in his Ranger with a 50 gallon fuel tank and his new 250 HP Mercury engine before needing to fill up. So they were bragging and advertising about their 4 mpg consumption.
silvertalon
Active member
jonathanr - 9/25/2017 7:54 AM
Noticed yesterday that my mileage range has dropped considerably on my XR4. I made about a total run of about 15 miles yesterday and ran out one of my half tanks in just that run alone. Are my carbs out of adjustment causing it to use more fuel now? I was thinking that at about 40 mph steady speed, I was getting about 25-30 miles out of one tank. I know most people are running newer engines, but I really don't have the funds to make the purchase and it is still running. Thanks.
Pull the air box (attenuator cover), off the front and each carb should have a small brass jet right in the top center. This is a mid range jet for what is called the "Backdraft circuit". It is for lowering pressure on the float bowl resulting in decreased fuel consumption. Make sure they do not have any dirt, grease or obstruction in them. A puff or two of carb spray cleaner should do the trick. 2- Add a bottle of ISOHEAT to each tank. There's a possibility of some water or moisture in your gas. Possibly need to have carbs cleaned out and wet set the floats. You should get a spray can of Quicksilver Powertune . With the engine running at about 1,500 rpm's, load up all three carbs until it is smoking like St Elmo's fire (about 1/2 can), then turn the key off and let it sit for about 2 hours. It should then be run wide open at the lake. This treatment should free up built up carbon on the exhaust ports, piston domes, clean your spark plugs and help free sticky rings. You can probably use a good compression test too. PM me if you need help. I have a shop and this is what I do- When I'm not fishing that is.
I hold two 12 gallon tanks. I am not really a WOT guy myself. I cruise around at about 40 mph most of the time. I know a two stroke sucks the gas, and this particular Merc is known to drink. I know when I came up and fished the chick last fall I made a run from Harrison bay up to skull island area and back and didn't use half a tank. The other day at Guntersville made about a 13-14 mile run and ran out in one tank. I will try the carb clean stuff and see how it does. I know I picked up some bad gas several weeks back while going to Lanier and finally got it cleared out while running back up the lake.
silvertalon
Active member
Unfortunately, there's not much you can do about an older 2 stroke and its fuel consumption except, decarbonize the motor, run mid grade (91 octane ), clean plugs and perhaps, a set of dual stage reeds by Boyesen or TDR.( Running low rpm's on the small 1st stage reeds can help). Best thing anyone can do is to buy a 4 stroke. An Opti or any DFI is a little better than carbureted or efi but its hard to justify the cost. Still need to fill the oil tank, spark plugs for an Opti are about 12 bucks each and more difficult to change and, if your air compressor goes out in a few years you are looking at a grand to replace it. A Mercury 150 efi 4 stroke will get up to 7mpg at slower speeds. Now tha'ts worth the upgrade.
Maybe I was off a good bit on my estimate. My revised guess is now 3 MPG at 40 MPH which is what I run 99% of the time anyway.Aries 181 - 9/25/2017 2:46 PM
I have an 03 XR6 and I'm guessing I get around 3 MPG at WOT and maybe 5 MPG at 40 MPH. A carb motor is what it is, a gas guzzler any way you look at it.
Bill
Bill
silvertalon
Active member
DFI's, Oprimax etc, are considerably better than carb or efi simply because there is no fuel scavaging. Scavaging is when raw full passes over the piston dome and out the exhaust port before the piston has a chance to close off the port and block it on its compression stroke. DFI (direct fuel inj in the cylinder head), fires the fuel plume just as the piston closes off the port resulting in little or no loss of raw fuel. Some fuel scavaging does occur in DFI at high speeds. I run my opti 225/21 Triton at around 3,600 to 4,600 rpm when leisure fishing and get much better fuel mpg than my 175 efi on my smaller 19' Champion. Still wish I had a 250 4 stroke...$$$
Ok, it appears that I did have some build up in the carbs. One thing that was really hurting it according to the tech is that the recirculation lines were really clogged up with carbon build up. He said this was causing a fuel dump issue. Decided to just bite the bullet and rebuild the carbs and replace the recirculation lines. To add, I had a vacuum line that was still attached from where a prior tech removed the oil injection. He said this was also causing less than optimal motor performance due to air being lost from it trying to pressurize the the line. Also adding a new fuel pump due to the ethanol eating it up. Compression still checked out at 130 on four cylinders and 120 on two. Not to bad for a 30 year old motor. Hopefully this will get it back to normal.
There are several ways to get better fuel economy. Here is a EFI 200 that I modified and put carbs on and took economy from 3 mpg to 4.5 mpg according to the owner. Couple of questions. 1. What octane fuel do you run? 2. Heads ever been cut? 3. Has a leakage test been performed? Link to engine http://www.chattanoogafishingforum....&highlight=carl&highlightmode=1&action=search