1990 90 hp johnson, losing power

i have just recently got my boat on the water with dismal results. <br /><br />All three times out on the lake i gun the throttle and it goes great, with lots of power @ 5500 rpm, then slowly looses power after about 45 seconds. it boggs down at about 2500 rpm and runs off plane. this exact scenario has happened twice before and am getting frustrated. there is a 13x19 s/s prop on the boat, which is a 16' bow rider. the engine has numerour new electrical parts, as well as rebuilt carbs.<br /><br /> if this rings any bells i would greatly appreciate help! ive been slowly working on this boat for 4 years.

Re: 1990 90 hp johnson, losing power

Fuel restriction??? Check fuel pump and inline fuel filter. Check all fuel lines from tank through and including bulb all the way to carbs for suppleness, cracks, and leaks.

Re: 1990 90 hp johnson, losing power

Also,make sure your fuel tank is venting.

Re: 1990 90 hp johnson, losing power

does this problem seem like a dead giveaway fuel problem?

Re: 1990 90 hp johnson, losing power

the bulb tends to be soft even when priming it alot, but feels like the fuel it moving through. i also rebuilt the carbs myself, a novice, and maybe i neglected something.....i appreciate your help on this-- johnson experts are few and far between

Re: 1990 90 hp johnson, losing power

where is the inline fuel filter, and how should i "check" the pump? thanx a bunch

Re: 1990 90 hp johnson, losing power

Have you checked to see if your motor is overheating?

Re: 1990 90 hp johnson, losing power

there would be a beeping if its overheating i think. besides i dont see how its related thanx

Re: 1990 90 hp johnson, losing power

If you can keep squeezing fuel through the carburetors and the primer bulb will never firm up,your float needles are not seating or you have fuel line leakage somewhere between the primer bulb and the carburetors.One other possibility is a faulty primer bulb.<br /><br />As Walker mentioned ,closely inspect the fuel line all the way back to the fuel tank to include the pickup tube for splits and fuel tank and engine fuel fittings for proper seal..If the upstream side of the primer bulb is sucking air ,the bulb will not firm up either.<br /><br />Solittles question is relative in that if the overheat alarm was not sounding because it was defective,that your engine has a s.l.o.w. feature that limits the rpms to 2500 in the event of an overheat.The temp sensor could be detecting the overheat but the alarm may not work.<br /><br />You can test the alarm by having the key in the 'on' position and locating and grounding one of the tan colored leads from temp sensor.The constant tone should sound.Do you get the alarm system check tone when you initially turn the key on?

Re: 1990 90 hp johnson, losing power

the seating of the float needles you speak of, could that be attributed to my novice rebuild? could you maybe explain this more in detail?<br /><br />also, if the bulb is faulty will it restrict the flow of gas and cause this?<br /><br />next, getting this straight, there cannot be any leakage or there will be some sort of restriction. does this include splits ect. in the tank but not under the surface level of the fuel in the tank<br /><br />all these things seem relavant, but it strikes me as weird that there is no problem revving it to high heaven in neutral. ie. > 2500 RPM

Re: 1990 90 hp johnson, losing power

Revving in excess of 2500 in neutral(no load) does not pose the same fuel volume requirements as revving to 2500 in gear under load.Just like traveing down a level road at 25 mph does not pose the same fuel requirement in your car as traveling at 25mph up a steep grade.Enough of that.Actually ,you should never rev an outboard over 2500 rpms out of gear ,out of water.<br /><br />To eliminate the possibilities of why the primer bulb will not pump up to firm and hold,you'll simply have to use the old fashioned process of elimination.One component at a time.Check the pickup tube for splits or leaks.If that's good, go on to the next possibilities mentioned.<br /><br />You never answered whether you are getting the initial alarm tone when key is turned on ,so we can't rule out an overheat and whether the engine is going into s.l.o.w.<br /><br />Yes a defective bulb can cause fuel flow problems.Is that what's doing it??Heck I don't know ,I can't touch it from where I sit.Does it go flat when the engine falls off?Can you pump on it and get the engine to pick up?If so your fuel pump may be defective and won't keep up at higher rpms.Check for a leaky pulse hose to fuel pump diaphragm.Crankcase vacuum and pressure pulses is what drives the fuel pump via a rubber hose.<br /><br />Can you bump the key primer repeatedly and get the engine to pick up? If so ,it is indicative of a fuel restricted carburetor ,since it allows fuel to bypass the carburetors and flow straight into the intake chamber.<br /><br />All of these questions are relevant.Troubleshooting is simply a process of elimination,but if you don't eliminate some things ,then the rest is just a shot from the hip.<br /><br />In summary,many different things could cause the very symptom that you are experiencing.Start with the easiest and work your way to the more difficult items.Good luck and tell us what you find.

Re: 1990 90 hp johnson, losing power

no the alarm isnt sounding, but ill check it tomorrow. i have a manual so it will be helpful. is the lead that i need to ground in theat vertical little bar of wires behind a color coded long plactic strip, is that the beige wire your talking about? <br /><br />next ill change the bulb, then check for leaks from the bulb to the pump, then from the pump to the carbs ect. <br /><br />a fuel resticted carb, is that the float pin issue you mentioned? i have a checklist in this manual and it says something about stuck floats (up or down). <br /><br />anyways im excited to check this stuff, but ill report back tomorrow

Re: 1990 90 hp johnson, losing power

Double check the fuel filter direction. They will work in the reverse direction for a while until they get a little clogged. I got ahead of my thoughts when I replaced fuel line and filter on my 90 hp Evinrude. It ran great first time out and then it would bogg down. I checked and noticed that my fliter was on backwards. Reversed it and it runs great! Worth a look.

Re: 1990 90 hp johnson, losing power

i took off the top carb and the gasket of the float bowl was rotted and letting gas leak out. this was the problem, and i made a new gasket out of gasket paper, and hope it holds up (the previous one looked to be rubber). i reassembled it and went out-- it goes like gangbusters. thanks for everyones help, it definately helped me since it was ultimately fuel related.<br /><br />ciao

Re: 1990 90 hp johnson, losing power

In your first post you stated "as well as rebuilt carbs." We can't be much help when we don't get complete and accurate info. I wouldn't depend on a homemade paper gasket on that carb. In fact, I'd get carb kits and rebuild both carbs. Glad you got it running right.

Re: 1990 90 hp johnson, losing power

One more thought, Sunbird, the 1990 90hp had plastic float bowls. A few years ago, I had to replace both of mine. The alchohol in the fuel warped the bowls, causing them to leak. The fix is new (old style) metal bowls and of course, since the plastic required a larger diameter bosses on the jets, matching jets for the metal bowls.<br /><br />Hope you already have the metal ones.<br /><br />good luck!