care and feeding of an older Merc 50 (4 stroke)
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=42915
Printed Date: October-06-2024 at 12:23pm
Topic: care and feeding of an older Merc 50 (4 stroke)
Posted By: 75 Tique
Subject: care and feeding of an older Merc 50 (4 stroke)
Date Posted: June-08-2018 at 2:01pm
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Speaking of old engines, as we were in the home made boat thread, I have a question that I didnt want to mess up that thread with. I am helping the old widow lady next door. She has a pontoon boat that has been sitting a couple of years (in the water) I told her I would get it freshened up for her. Surprisingly, the engine (2003 ish, merc 50, 4 stroke) started right up. Even the battery was still charged. Will idle forever at the dock and will run forever out on the lake between 2000 and 3000 RPM (plenty for tooner cruising) But at over 3000 to 4000, after about 5 minutes or so of running fine, it starts cutting out and surging. I can pull it back to idle and its fine. Accelerate and it starts acting up again. Sounds to me like fuel delivery issue. I was thinking fuel filter maybe. Youtube shows me there is one tucked in the bottom of the engine housing but I didnt see it. Anybody have any ideas where to start? It had old gas in it, which I left in it, but have added a bunch of new. ------------- _____________ “So, how was your weekend?” “Well, let me see…sun burn, stiff neck, screwed up back, assorted aches and pains….yup, my weekend was great, thanks for asking.” |
Replies:
Posted By: JoeinNY
Date Posted: June-08-2018 at 3:04pm
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Have you opened the fuel tank vent? There is probably a filter in there - that could be changed but more likely standard carb rebuild issues, assuming you opened the vent on the fuel tank! I would put fill it up with new gas and put seafoam in the gas tank, a relatively ample amount and try to run it clean before messing with it further than that. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: JoeinNY
Date Posted: June-08-2018 at 3:06pm
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and seriously anything newer than 1994 is definitively not an older merc ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: outerbanked
Date Posted: June-08-2018 at 3:19pm
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Check you fuel hoses. The ends can crack and suck air. I have seen older hose compress and the plastic quick clamps will be loose. I replaced my hose with a universal bulb kit and was not careful with the Teflon lined hose.  It took a season or two to work the glue loose, but similar issue at max flow. |
Posted By: 75 Tique
Date Posted: June-08-2018 at 3:27pm
Thanks Todd. I'll look into that too. ------------- _____________ “So, how was your weekend?” “Well, let me see…sun burn, stiff neck, screwed up back, assorted aches and pains….yup, my weekend was great, thanks for asking.” |
JoeinNY wrote:Posted By: scootdogydog
Date Posted: June-08-2018 at 3:28pm
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Same thing happened to mine during a bachelor party a couple years ago. If pumping the primer bulb helps the situation, check the fuel filter, crud in the tank, and finally the fuel pump. I went through all of that and it was the fuel pump. Mine was a big foot 50hp efi ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=7183" rel="nofollow - 1999 Python 1980 Ski Tique 1968 Mustang WIP |
Posted By: JoeinNY
Date Posted: June-08-2018 at 3:40pm
If you haven't seen a carb then it probably doesn't have any and is efi, in which case follow the advice above. If it has a perm vent make sure its not full of spider sacs or bees nests. I would still start with the seafoam before getting intense into anything else if it behaves nicely at low speeds. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: 75 Tique
Date Posted: June-08-2018 at 3:51pm
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Thanks Scott. Admittedly Joe, I have not done much homework on it yet. Is the carb on the front of the engine? If so, I havent explored that area too much as it is buried in an alcove, like this one, plus, like I said, in the water, so its not real accessible. Scott, the fuel bulb is also in the alcove, so going to be hard to access while underway. I guess I've got to find a small friend. Back to youtube.  ------------- _____________ “So, how was your weekend?” “Well, let me see…sun burn, stiff neck, screwed up back, assorted aches and pains….yup, my weekend was great, thanks for asking.” |
Posted By: scootdogydog
Date Posted: June-08-2018 at 3:55pm
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Larry, what is preventing you from relocating the primer bulb, for testing purposes, or using a separate gas can to rule out issues with the tank? ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=7183" rel="nofollow - 1999 Python 1980 Ski Tique 1968 Mustang WIP |
Posted By: Gary S
Date Posted: June-08-2018 at 4:49pm
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And if it has a built in tank it most likely will have an anti siphon valve too. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: 75 Tique
Date Posted: August-21-2018 at 11:51am
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Update, like I said in my Gremlin thread, I know people like to hear if/how problems were resolved. So my approach after the advice above (thanks to all that provided) was to do nothing. It ran fine at tooner cruising speed, so for now I left well enough alone. It has been running so well at tooner cruising speed, I thought maybe fresh gas may have cleaned it out, so last week I did (for the first time in a month or so) another "high speed" run. Just like before, it crapped out, only this time it did not recover. Oh swell, now it doesn't even go tooner cruising speed. And of course the timing was terrible in that have company coming. So I decide to dive into it. I stop at the parts store on the way home and pick up more Seafoam (already poured a can in) and some carb cleaner. At this point, it didn't even want to start, but I finally coaxed it. I took the cowl off and I might as well have been looking at one of Tim's Plane jet engines. I saw nothing familiar under there. At the dock at high idle it kept surging 5000-1000-5000-1000, and would not idle. I took Scotts advice and tried pumping the bulb to see if that helped. It didn't, but it did reveal a significant kink in the fuel line. I straightened it out, purred like a kitten. Started easier, idled smoothly, revs nicely. I am not going to "high speed" test it again until company comes and goes, but I am guessing that kink was the problem. I'll let you know if I find anything different. A somewhat amusing anecdote. When I stopped at Advance Auto, I told the guy what I was up to. I could tell he was not a boat person, but he shared a story. He was out fishing with a friend on a big local lake. He said that boat started doing the same thing. They limped home with the trolling motor but when they got back to the dock, looked things over and found a kinked fuel line. How about that? Oh another little twist to the story. The pontoon boat is now mine. She decided she had no use for it and was disappointed her family had no interest, so she "made me an offer I couldn't refuse" Those of you that know me and like to rib me, can imagine just how good an offer that was. ------------- _____________ “So, how was your weekend?” “Well, let me see…sun burn, stiff neck, screwed up back, assorted aches and pains….yup, my weekend was great, thanks for asking.” |
Posted By: TRBenj
Date Posted: August-21-2018 at 12:30pm
| Score. How much did she pay you to take it? |
Posted By: 75 Tique
Date Posted: August-21-2018 at 12:44pm
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Not too much. It really isnt that bad. (I think I need to order a Judge Smails Skipper's hat, though)   ------------- _____________ “So, how was your weekend?” “Well, let me see…sun burn, stiff neck, screwed up back, assorted aches and pains….yup, my weekend was great, thanks for asking.” |
Posted By: Gary S
Date Posted: August-21-2018 at 1:36pm
so now you’ll be able to fit in with the neighbors when you pull tubes  ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |