1975 Evinrude 135 hp falls on face at high rpm??

[bman571]

So, I bought a 1975 Browning Aerocraft, it has a 135 horse Evinrude outboard on it. It starts and runs good enough, the only problem is that at cruising speed, it will literally fall on its face like someone shut it off. If i pull back on the throttle quickly, it wont stall, if i dont it stalls, and starts right back up again. It is not a spark issue, because it runs great, no spit or sputter. If i catch it in time and just let it cruise at very low crawl rpm for 30-45 seconds, it will go right back on plane and rev out fine. It feels to me that it is running itself out of gas at high rpms. The tank is 18 gallons, and it seems the lower the fuel level gets the more frequently it does this. Also when it is rough out it seems to do it more also. These may or may not have anything to do with it. Any ideas to fix this problem would be great

P.S. It has new fuel line from the tank to the engine, and a new fuel pump. Thanks Again!

 

[ezmobee]

Re: 1975 Evinrude 135 hp falls on face at high rpm??

Possibly dumb solution but are you sure your tank is venting correctly?

 

[bman571]

Re: 1975 Evinrude 135 hp falls on face at high rpm??

How will I know if it is venting properly?

 

[ezmobee]

Re: 1975 Evinrude 135 hp falls on face at high rpm??

One sign could be that the primer bulb gets sucked flat.

 

[emdsapmgr]

Re: 1975 Evinrude 135 hp falls on face at high rpm??

A weak fuel pump will not provide enough fuel to run the engine at high rpm's. The carb bowls may be running out of fuel. The pump may not supply enough for constant high rpm running. It will refill them at idle, and permit you to run it up to top rpm, then run out of fuel again. Try constantly priming the fuel hose bulb-it will force fuel around the pump into the carbs. If it runs high rpm by constant priming, then you may have a weak pump.

 

[bman571]

Re: 1975 Evinrude 135 hp falls on face at high rpm??

Thanks, but it has had 2 fuel pumps and has had the same problem with both, it doesn't always do it either, sometimes it will run 30 minutes and not do it, and sometimes it will do it every 2 minutes.

 

[ezeke]

Re: 1975 Evinrude 135 hp falls on face at high rpm??

I agree with emdsapmgr that it sounds like a fuel pump problem. The afterrmarket replacements are not strong enough and the OEM were OK when in good shape but you need to be sure that the screen is clear, that the pulse hose is absolutely air tight, and that there are no air leaks in the fuel lines.

You could also have floats valve clips missing that connect the float arm to the float needle (click the thumbnail).

You might want to pull the fuel pickup from your tank and inspect it; it may have holes in the line. Also check your anti-siphon valve, if it is the original tank the anti-siphon valve should be replaced.

 

[emdsapmgr]

Re: 1975 Evinrude 135 hp falls on face at high rpm??

If it is not the pump, look for a fuel restriction, like a defective anti-siphon ball valve or bad ball valves in the fuel hose primer bulb.

 

[bman571]

Re: 1975 Evinrude 135 hp falls on face at high rpm??

First, I would like to say thanks to everyone for their help!!
I removed the fuel tank, and removed the pickup tube, and sure enough it was plugged. I don't even know how it ran as good as it did to be honest with you. I replaced the pickup tube, and the anti-syphon valve and the boat runs like a top!! Thanks again for all the ideas and help!!