New gas line increases speed

After noticing I had the old mercury fuel line(red writing on it/ethanol unfriendly), I replaced them from the selector switch to the motor. I cut up the old line into small pieces to examine and was shocked what I found. The inner liner not only had completely separated from the hose, but was rock hard in several places and cracked to pieces. Luckily my ad-on water/fuel separator was catching these bits of debris before they wound up going thru the engine. Now heres the weird thing. Ive had no issues with the motor running or idling with the old fuel line except for the fact that the boat wasnt as fast on top end as I thought it should be. I have a 00 Sabre with a 00 175 efi. I was running 64.7 turning a new tempest plus 25 in perfect condition at 6000 rs, 1/2-1/4 tanks gas, all tackle and me(190 pds) and motor set at about 3.6" below pad. Since the new fuel line has been installed, I ran it one day and hit 68.7 @ 6,000 rs and another day hit 69.4 at 6025 rs. All these speeds are gps too by the way, although my tach and psi are analog. I realized that the old line could have restricted the fuel flow and that could have been slowing me down, but the wierd thing is that it didnt affect my rpms before. Im finally satisfied with my setup. My top end speed at 69.4 works out exactly to 9% slippage on the performance calculator with 1.87 gears. It feels nice knowing that my 11 year old Merc can still do what it should do new!!Last edited by arkriverrat on February 22nd, 2011, 3:34 pm, edited 1 time in total.

This topic has 4 replies, 3 voices, and was last updated 14 years, 2 months ago by arkriverrat.

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February 22, 2011 at 3:53 pm #390767

jignpig
Participant

I have an additional water/fuel separator too, that was on my boat when I bought it. I change it out yearly. Also changed out the fuel lines as well. 96 model Mariner 175 EFI posting similar numbers. Kinda neat to see these older engines still kick out some spray!96 Eyra/12 Mercury 175 Pro XS with 2015 single axle trailer2017 Victory Gunner

February 22, 2011 at 4:01 pm #390770

xm sean
Participant

Hoping for the same results on my end….. I have a 2003 200 opti on my P4 and getting 68 at best. I just had some big upkeep done including the fuel line that was all gummed up like yours….. Glad to hear it worked out for you…. I should know in a few weeks as it starts to warm up some more over here.Last edited by xm sean on February 22nd, 2011, 4:03 pm, edited 1 time in total.

February 22, 2011 at 4:44 pm #390773

arkriverrat
Participant

After seeing the affects on two different sets of fuel lines(one set on my duck boat w/ 25 johnson and the other on the cat) I now go out of my way to buy non-ethanol gas for both boats. I dont trust it even though I used Stabil. One of those deals where Im planning on keeping my boat for a long, long time and as long as I can get non-ethanol, thats what Im going to use. I didnt mention about my duck boat before, but I have a 14 semi-v with a 97 25hp johnson. It has a bow mounted gas tank to help with weight in the back of the boat and thus a 13ft fuel line. With the original fuel line, it would start, idle, and run 3/4 throttle perfect. The problem occurred when you ran wot. Because the old fuel lines were completely collapsed the motor was drinking gas faster than the line could supply and the bulb would collapse and the motor would die or run slower because of the restriction. Replaced feul line with johnson/evinrude line, 13ft @ $6 A FOOT *ouch*, and has ran fine since. I HATE ETHANOL!!!!!!!!!!!!!!! ITS DONE NOTHING BUT COST ME MORE MONEY

February 22, 2011 at 4:57 pm #390776

arkriverrat
Participant

xm sean wrote: Hoping for the same results on my end….. I have a 2003 200 opti on my P4 and getting 68 at best. I just had some big upkeep done including the fuel line that was all gummed up like yours….. Glad to hear it worked out for you…. I should know in a few weeks as it starts to warm up some more over here.When I bought my cat it had a 24 trophy plus. Everything was great except for top end. 63 @ 6000wot. I tried everything: bought props, borrowed props, played with jackplate, moved weight inside boat. Going to the 25 tempest plus increased speed to upper 64s but was still not happy. I was about to pull my hair out thinking my motor was weaker than average, but not now, shes actually stronger than I gave her credit. Ive never stripped her down and ran wot, (flipping deck is packed with bait boxes,heavy heavy). I would also love to try a 25 fury. I believe that prop would be the nuts for my setup as I really need to loose 150-200 rpms on top end to be comfortable running at wot more!! I think it would do a little better than 70 the way it is now and with some fine tuning on the plate…who knowsGood luck and new fuel lines may be the ticket!!
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