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Starving merc

J

Jdelkins

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I have a 91 model xr4 150 merc . I bought this boat about 4 months back. A 1991 gambler gt183 . At first it was over proped and I have that one fixed . But since I'd get a couple days a running great to acting like no gas . I have replaced filter , then primer , then inline filter between pump and carbs and then finally the fuel line as I cut it open to find it had deterioated bad and pieces had blocked fuel filter again . Got a couple more good days and now it's down to cranking and idling great , runs smooth to about 3000rpms then acts starved again . Open to ideas
 
Do a compression test.----Then check for spark on all leads.------And stop running it now and determine the cause.-----Running with a plugged carburetor can do big $ damage.
 
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Sounds like ethanol deterioration, fuel pump likely needs kit or replacement. Some other techs here don't mind ethanol, but I'm never using it again in my own equipment. Check out this photo of a damaged plastic line, plugging off the coupling with the inner liner literally "melted". More photos forthcoming of "e" damage as I dig out my parts.....crank seals.....diaphragms, hoses, plugged jets and carbs, water pump impellers, OMC VRO's, scored pistons and cylinders. Don't listen to me......just "google up"....."what does ethanol do to rubber and plastic"?
 
I run ethanol free fuel only , but guess previous owner didn't. I sliced the old fuel line and the liner was flaking and my filters were full of the stuff , so I'm guessing if it got to filter between pump and carbs that it probably is all over the inside of pump . I got compression tester yesterday , but had a death in family so didn't do it today . I do appreciate all the help yall give here
 
Okay, brother, prayers are with you, hope that things go okay.
If the crap got past the fuel filter and into the pump, then its likely in the carbs too. But try the pump and see what contamination seems to have gotten through.
 
Well I'm back , ok I'm going run a compression check on the motor , is there a acceptable range ? Does it need to be in the water and running or can it be done in the yard on a water hose ? First I will remove pump and open it up . Is there a way I can post pictures here ?and thank you for the prayers
 
Okay, I hope things are going better for you, let's fix this Merc. Expect help from Racer, he is one of our top techs.
Compression test, all plugs out, trickle of water to lube water pump, crank with throttle slightly open, full battery. Keep hands and hair clear...(in my case, ha!)
Go to "advanced" at bottom of message, add attachment from phone, etc....but has to be a pretty small file for the photos
Compression within 10 psi per cyl. and maybe 115 to 135 psi, depending ambient or motor temp as well as accuracy of the gauge.
 
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Well my compression on all 6 were at 90 to 95 . The fuel pump was not only full of those pieces of liner from fuel line but was also loose and about to fall off . I also found two vacuum hookups on right side with no line or not plugged . Dont know if it was lines to old oil injection which previous owner removed .
 
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I'll be first go admit I'm no outboard mechanic , just a 60 yr old disabled man trying to keep this boat going . So I thank you all very much for all your help .
 
So you mix the fuel, I guess? Maybe the previous owner ran low on oil and that is why the low compression. That is exactly what happened to me a couple years ago. Now my compression is 90 to 95, but it still runs with lower power than before the broken injection line. In both your case and mine, we are likely looking at an overhaul. You have a new compression gauge too, right?
 
Yep , bought a new screw in gauge . When it would open up and run ,it ran great and didn't seem low on power but who knows . I do mix the oil and gas , never trusted oil injection myself . Does those vacuum hookups pull enough to effect the running ? It has those crazy NGK plugs , not sure if any are fouled so they get replaced next .I'm not hard on a boat and try to take care of it , hope it holds together for a while . Is it a difficult rebuild ?
 
95 psi is fine for a V6 motor no need for an overhaul. The gray fuel line is garbage it will disintegrate with regular fuel in it. That line is notorious for seperating from the liner Buy a good quality fuel line for your replacement a good quicksilver or Brp. A 30 yr old fuel line just goes bad ethanol is not to blame for everything. As far as ethanol and plastic, car fuel pumps aree submerged in ethanol for yrs with no damage to them. Rubber is.not used in fuel systems any more. Your line tot old and.was not maintained and that is what happend. Fuel line went bad long before ethanol came around. A lot of mechanics like to blame ethanol for everything easier to blame ethanol I guess.
 
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Mr. Delkins, I have this disagreement every time Mr.Scott and I meet on a post. Ethanol is one of the most damaging additives ever presented to fuel. Go ahead and Google it up. I think Mr. Scott, Don't get me wrong, I love this guy and all his talent and experience, but I think Mr. Scott is blind to the proven destruction of ethanol in our fuel. Check it out on Google, just ask Google "What does ethanol do to rubber and plastic"? Besides that, it produces less power and is an "unstabil substitute for octane additives that are normally incorporated in quality non oxygenated fuels. Ask yourself this? Why is ethanol illegal to use in airplanes?
 
For one thing ethanol is an octane booster so it does not create less power in e-10. 20 years ago yes ethanol damage was prevalent. The damage showed up rather quickly but now 40 yr old parts are failing. You can't blame old age or bad quality parts on the ethanol anymore. Now it is more of a lack of maintenance nothing lasts forever and wear and tear is normal. Your fuel line will not last any longer with 91 octane non e fuel. Look up what is added to fuel nowadays ethanol is the least of the problems. Ethanol is illegal in airplanes because it absorbs water the same way gas line antifreeze does.And if you look timguy is the only tech on here who constantly blames ethanol for everything.
 
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Well it's like the great Ford vs Chevy debate . I do appreciate all the thoughts and opinions you guys have , believe me ya'll know a hell of a lot more about outboards than I do . Several years back I owned a weed eater and mower that dang near needed carbs rebuilt each year ,the mechanic at time told me to stop using ethanol as with this type of equipment it has a tendency to sit for long periods. So after that I use ethanol free fuel in all my small engines and outboards and when I shut down for winter I add stabil also . No carb rebuilds since . So whether it's good now or not , it feels cheaper to me to not run ethanol than rebuilding carbs every year . By the way I ran that weed eater till last year , it gave me 23 years of great service . So thank you both for helping this old guy try to figure out this old mercury
 
Pretty much all our stations sell it around here , just about .20 cents a gallon higher . I live out in rural area and can even get it at out local co-op. But at moment I'm enjoying regular unleaded being under 2.00 again
 
Mr. Delkins, where are you located? Its still $2.60 a gallon here in Northern MN. Ethanol blends are $2.30. I am hoping to order 1000 gallons for my home non oxy tanks, very soon. Last of my 7 year old fuel has just been used up.....still fresh up to the last drop. You folks in the bigger cities are really getting "hosed".
To respond to Mr.Scott, 100% correct, Illegal to use ethanol in your airplane, because of the ability for the fuel to mix with water. So why would I want that stuff in my 30 or 40 year old boat, snowmobile, jet ski, lawn mower, or collector car..?....only if I embrace problems related to fuel. If I'm the only tech here that doesn't like ethanol in my customers or my own equipment, then so be it. Do you remember the poem by Robert Frost: "The Road Not Taken"? Well.....that has been me.....I'm happy with it and where it has led me.
 
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Well Mr. Guy I live in western Arkansas, this morning I put 25 gallons in my truck at a whopping 1.97 . Lol I love it . Name is Elkins by the way . Hope temps stay in high 60s through weekend so I can try boat out . Is there a specific spark plug I should use , and what's best way to check coils ?
 
Sorry, sir, ha! Mr. Elkins, you are a lucky dog to get fuel so reasonably priced, I hope its migrating up north. I am a Champion plug guy, perhaps because I get great lifespan from them. I use Amsoil for my 2 stroke equipment too, and that surely adds life to the plugs as well as virtually eliminating exhaust deposits in the combustion chamber and exhaust. To check coils, I check first the spark to see if it can jump with a nice white/blue color.....at least 7/16". Then if something is not looking strong, I will check coils with the procedure outlined in CDI electronics free diagnostic manual....
I will find the link for you. All you need is a simple multi meter.
Just Google up. "CDIelectronicsmanual". All the info is there for you. CDI makes electronic components for many applications, mostly marine, but you can also get replacement parts through this site, marineengineparts.
 
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Which champion plugs and what gap do you recommend? I think I have an spark tester made from an testing light , worked good on my old mustang's and jeeps . Coils dont seem hard to replace . What was your thoughts on those 2 vacuum hook up with nothing on one side of them . I tried to post pictures but guess to big
 
QL6VC gap is fixed. Vacuum hook up? My black max is in the neighbor's indoor arena but it is a bit older than yours anyway, but sounds like it could be part of the disconnected oil injection system. If so, just make sure that they are plugged off. My 150 black max is 120 psi each cylinder, but my 115 that was run low on oil is 90 psi. I intend to rebuild the 115, but the black max is sweet. My wife bought it on an old Starcraft 21 footer. We will use that boat for freighting into our remote NW Ontario resorts. My wife is a Philipina and she loves boats even more than me. She was born and raised in a house on posts, above the ocean.
Ps. I went to the Philippines to shop for boats in 2000, couldn't find what I was looking for, so I gave up on boats and found a beautiful woman instead.......as luck would have it.....and a Jehovah Witness to boot!
 

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That is for Airplanes not outboard motors!!!!!! By the way the writing is on the wall with E-85 now being sold ethanol is here to stay.
 
Maybe with your brilliance comes stubbornness. Readers of course will make their own choice, and I will always respect your advice here.......well MOST of IT!......I treat everyone like I would wish to be treated, with respect and dignity, but when advice is made that is not founded on facts, but feelings, it hurts me. For that reason, I will continue to suggest avoiding any ethanol in marine, small engine, vintage cars, and seasonal equipment.......yes......and airplanes, unless you have a "glider". Wilbur and Orville Wright, would agree with me.......I think!
 
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Lol well due to my own experiences I will stay away from ethanol products but to each their own . Let them make that choice on their own .I respect all the opinions and thoughts from the people on here as I have no knowledge on this stuff . I'm not afraid to try to work on it myself or ask for help . So I appreciate all of yall regardless of their beliefs on ethanol .
 
So congratulations Mr. Guy on your prosperous trip to the Philippines and finding you beautiful wife . Wish yall many years of happiness

Ok I got pictures to post on next page . One is junk from line and pump and other two are the vacuum
 
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timguy said:
Maybe with your brilliance comes stubbornness. Readers of course will make their own choice, and I will always respect your advice here.......well MOST of IT!......I treat everyone like I would wish to be treated, with respect and dignity, but when advice is made that is not founded on facts, but feelings, it hurts me. For that reason, I will continue to suggest avoiding any ethanol in marine, small engine, vintage cars, and seasonal equipment.......yes......and airplanes, unless you have a "glider". Wilbur and Orville Wright, would agree with me.......

Well next time i am flying my boat and it falls out of the sky because I put ethanol in it. I will post on this forum how right you are.
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