Evinrude 175 Ocean Pro bogging above 4000 Rpm's

gwgautney

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Aug 28, 2013
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I have a 98 !75 Ocean Pro that has been giving me some issues. It runs fine other than when you get it above approx. 4000 rmp's. I restored boat over the winter and before I started there were no problems with it. When I got done with it and took it out the first time it ran fine at 4000 and below. Once you give it more throttle it will start accelerating for 10 or 15 seconds but then it will start bogging down almost like it's starving for fuel. I have rebuilt carbs and had it tuned up at shop due to an idle issue I had. There was fuel in the tank when I let it sit. I treated it with stabil and then put some sea foam in it and ran most of that out. It's a 37 gallon tank and I just put 29 gallons in it last weekend so I feel like all the old fuel is gone. The only thing I did with tank when I was working on it was pull out the pick up tube and inspect it. I pulled the screen out of it and checked it out. Is it possible that I messed screen up when I put it back in and that is causing it? Also I changed anti-syphon valve. I did not change hose from tank to the motor should have but didn't. Any advice on where to look would be appreciated.
 

Chris1956

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Mar 25, 2004
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Pump the primer bulb when running at 4000 RPMs and see if it gets better. If so, you have a fuel delivery problem. If not, maybe you have electrical problem?
 

gwgautney

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one thing that happened the other day was when it started bogging it got worse like it was out of fuel at lower rpm's and I tried to pump bulb and it would stay flat. I took hose off of it and let it reinflate then reconnected hose pumped it up and it was fine after that except above the 4000 mark
 

boobie

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Does it go flat after the 4000 mark. You could also have a bad primer bulb. Take it off and shake it. If you hear a rattle the check valves are loose.
 
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gwgautney

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Aug 28, 2013
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going to pull the floor hatch this week I guess and replace fuel line and check pick up tube do yall think it could be a hose collapsing?
 

gwgautney

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I pulled console and fuel tank access panel this evening and replaced fuel line. the old one didn't appear to be bad but it looked aged don't know if that was issue or not. I pulled the vent hose and blew through it no problems there and Ipulled pick up tube and inspected it it seemed ok. I didn't see any obvious issues. I guess we will see this weekend when I put it in the water. I also pulled about a half of a quart of fuel and put it in a glass jar and did not see any water thought that may have been a problem.
 

Bosunsmate

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id take out a spare tank so you can then narrow it down if you havent fixed it
 

gwgautney

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ok so I took it out a couple times this weekend after changing fuel line and all. im leaning more towards this being an electrical issue rather than fuel because the way it is acting.. You can give it just about all the throttle when you take off it will jump up on plane and run hard for a few seconds and then its as if it looses power itermentitly or however its spelled . also when im running that steady 4000 rpm's now it seems to be getting worse doing the same thing as above 4000. Im lost don't know which way to look now. any help will be appreciated
 

gwgautney

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and I may be in left field I may be missing something. I did not run it on external tank yet one I was going to borrow was being used
 

Chris1956

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What you have described could still be a fuel restriction issue. Does the primer bulb go flat? Can you pump the primer bulb and keep the engine revving?
 

gwgautney

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Primer bulb doesn't always go flat but on a few occasions i have had to pull hose of to allow it to reinflate but it doesn't seem to go flat when running. I didn't have aNybody with me to pump on it when running at high rpms
 

gwgautney

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Aug 28, 2013
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Crazy question here would air blowing into the vent line through the vent on outside off boatcause any of this i noticed it is turned more down rather than towards the back of boat
 

gwgautney

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Aug 28, 2013
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Ok so I took her out this evening and took an external tank and bam she ran like a top. I swapped back and forth between external and my onboard tank and it messed up every time I went back to onboard tank.. I got to thinking it could be water separator so I bypassed it and no changed still bogged. Went back to external tank and ran wot at 5100 rpm's which is low but I think that is just an adjustment issue that I will tackle later. So bottom line it is in the tank so what could it be? As far as the vent line goes you can blow straight through it when it was unhooked. You can blow in it while its hooked up and it will push pressure back to you. Also when you fill boat up it will spill over fuel out of vent. I've replaced fuel line from tank to motor. When I was redoing boat I replaced the anti-syphon valve is it possible that I got a bad one or that it is the wrong diameter? Or could it be trash in the tank from sitting up. Lost now don't know where to go from here.
 

gwgautney

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while i'm on it if anybody could tell me how to adust the throttle linkage on this motor I would appreciate it or do I need to start a new thread
 

hardalada

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Jun 24, 2015
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The only thing which you have in your fuel line on your original onboard fuel system that you do not have on your borrowed tank is the nice new non-return valve you just installed.:confused:
Is this non-return valve sized big enough to allow sufficient fuel to flow at WOT?:eek:
Take the non-return valve out and replace it with a straight length of fuel pipe (or your old non return valve) and test run the boat again....:joyous:
 

gwgautney

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Aug 28, 2013
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That was my first thought i will be changing it out this evening thanks
 

gwgautney

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Aug 28, 2013
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Ok so apparently the original anti siphon valve that was on my tank must have either not been a valve our had been altered. I went to dealer and purchased an oem valve and still had problem. I have nowreplaced that with just a house barb deleting the anti siphon valve. I took it out yesterday evening and she ran great on my tank.
 
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