Johnson 25HP issue

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jonmac3569
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Johnson 25HP issue

Post by jonmac3569 »

I have a 1975 Johnson 25 HP. It did not run when I inherited it. It had been setting up for 10 years. I changed the lower unit oil, plugs, starter pull rope, rebuilt the carb and changed the impeller.

It idles very well now and runs well at lower speeds. If I try to open it up, it will start "choking" and seems that it is not getting enough gas. Initially I was using one of the replacement fuel lines with the priming bulb built in. I changed back to the original hose and it ran a little better. But at higher speeds I still need to reach back and pump the bulb as I am going down the river to keep it running.

Obviously sounds like it is not getting enough fuel. Any ideas why?

Thanks

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crazymanme2
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Johnson 25HP issue

Post by crazymanme2 »

Fuel pump bad #-o
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baseball_guy_99
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Johnson 25HP issue

Post by baseball_guy_99 »

Agree with crazy. Get yourself a fuel pump rebuild kit.

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Captain Ahab
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Johnson 25HP issue

Post by Captain Ahab »

It is not the fuel pump - on that engine they either work or they do not - since it runs it works

you have a bad connection on your fuel line

Try a new line or new connections and you will be just fine. i have the exact same problem on my 25 hp Evinrude
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jonmac3569
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Johnson 25HP issue

Post by jonmac3569 »

The fuel line that goes from the exterior hose connection to the fuel pump I did not change. I changed the one that goes from the fuel pump to the carb. It is possible it is slightly smaller in diameter than the original. The original was old an dry rotted and appeared to have stretched so it was hard to match the size. Guess also possible the line to the fuel pump has an issue.

I guess I will try replacing the that line and cleaning the pump first. I guess if that does not work I can always rebuild the pump.

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jonmac3569
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Johnson 25HP issue

Post by jonmac3569 »

I changed out that fuel line and it was dry rotted. I could break it just by bending it so maybe air was getting in.

Does anyone know if they make a rebuild kit for this particular fuel pump on this motor? I checked several sites and found many rebuild kits but I haven't found one that says it will fit this particular motor.

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Pappy
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Johnson 25HP issue

Post by Pappy »

There are kits available for most of the OMC pumps. Some pumps do not have a dedicated kit available, however all the necessary parts/pieces are available with other kits. If you have a dealer available close to you take the pump in and have them match it up to either one of the square pump kits or the other shape.

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jonmac3569
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Johnson 25HP issue

Post by jonmac3569 »

Thanks for the reply on the pump, I will try that.

Got another issue now. I replaced the other fuel hose and all the connections and took it out for a try. It was basically doing the same thing. One time it died, tried to recrank and I got nothing. I looked in the water behind the motor and there was oil dripping in the water.

See the pics below. There was black oil coming out of the ports in the lower unit and the all the areas the water is pumped through. The oil was pretty black, I had just changed the lower unit oil a month or so ago. Why would it be that black already? Also, is this a broken seal in the lower unit?
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1nov11c.jpg
1nov11b.jpg
1nov11a.jpg

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jasper60103
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Johnson 25HP issue

Post by jasper60103 »

The good news is you don't have a lower unit leak. That's a drain hole in the lower unit. Perfectly normal to see some unburned fuel drain out like that. But it sounds like you're dumping a lot of fuel. Unfortunately, I don't know why. Maybe it needs a long run at WOT since it setup so long?? What fuel ratio are you running? Hopefully, some of the pros will chime in.
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lckstckn2smknbrls
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Johnson 25HP issue

Post by lckstckn2smknbrls »

You should try running fuel with a lot of Sea Foam in it to remove the carbon build up. Search "Decarbing".
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jonmac3569
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Johnson 25HP issue

Post by jonmac3569 »

jasper60103 wrote:What fuel ratio are you running?

50:1
Last edited by jonmac3569 on 01 Nov 2011, 22:25, edited 1 time in total.

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jonmac3569
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Johnson 25HP issue

Post by jonmac3569 »

lckstckn2smknbrls wrote:You should try running fuel with a lot of Sea Foam in it to remove the carbon build up. Search "Decarbing".
Thanks, I will check that out

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jonmac3569
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Johnson 25HP issue

Post by jonmac3569 »

I ordered a rebuild kit for my fuel pump, rebuilt it and took it out today to try it out. It is doing the same thing. Runs fine at idle and lower speeds but when I give it more gas it will choke unless I pump the primer bulb. I got a couple different answers when I originally posted this. Some seem to think that it is the fuel pump, others said that the fuel pump "either works or doesn't". I also checked all connections and replaced all the fuel lines. I had a friend that rebuilt his with the same issue, didnt work, then replaced the pump and it worked great. (different motor and pump)

Can anyone shed some more light on this? Just want to make sure before I spend $80 on a new fuel pump. My pump is in the pic below (before the rebuild).
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6 nov 11.jpg

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Pappy
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Johnson 25HP issue

Post by Pappy »

The pump either works or it doesn't is an accurate description! The fact that you can pump the primer bulb and make the engine run is indicative of a "bad" fuel pump. You are taking the place of or eliminating the fuel pump when you are pumping the primer bulb. The sole purpose of either the primer bulb or the fuel pump is to keep the fuel bowl full and the needle and seat in the carb closed.
Am betting you haven't checked the pulse line and fitting that supplies and powers the fuel pump. Check and make sure the line has no cracks or pinholes. Check the fitting and make sure the port is not clogged or closed. Lastly, there is myriad of ways to assemble that pump incorrectly........you have probably figured that out by now. Any way but the absolute correct way will give you the same issue. There are small umbrella valves in that pump that must be there as well. Have been through several that at least one was missing from. You can remove the supply line from the carb once you have primed and started the engine and take a look at the fuel flow if you want to verify operation.

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Canoeman
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Johnson 25HP issue

Post by Canoeman »

Before you sink anymore money into this go over to https://forums.iboats.com/forum.php , register and go to the Johnson section, Make your post thorough and informative, serial number, make and model and explain what is going on in detail and what you have done to try to remedy it... someone over there will help you out.

let us know what you find out..

that is if pappy's advice doesnt work out..

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