My motor let me down all last season!! Help me fix it!!!

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Oct 27, 2021
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My motor acted up all of last year and with the upcoming season I want to get it fixed. I called around to all of the Marine Mechanics in my area and no one would either call me back or had any availabilty because of a lack of labor. So hopefully with the help of this forum I can diag and fix my engine. I will go into as much detail as possible.

My boat is a 1996 Spectrum with a 1997 Yamaha T9.9ELRV. When I purchased this boat the previous owner had everything in the boat running off of one 12v battery. That was the engine, trolling motor, 2 fish finders(Garmin 7SV's), bildge pump, light and did not have a functional livewell.

The issue that I have had with my boat is that when I would accelerate to full throttle the motor would start to sputter out and die. I have gone through a process of trying to trouble shoot this issue, below is everything I have tried so far. Please note that I am currently in the process of redoing this whole boat.

1. At first I believed this was a fuel delivery issue so I replaced all of the fuel hoses, the hoses in the engine itself, fill hoses, hoses from the tank to the engine and a new primer bulb. When running at full throttle I noticed that my bulb would never truely stay hard. I was able to keep the enigine from dying multiple times by reaching back and priming the bulb.
2. When replacing all of the fuel lines did not fix the issue my next guess was the fuel pump. I looked the parts up on Sim Yamaha and ordered a new fuel pump. Since 1997 the fuel pump had been replace with a new verison. The new fuel pump has 4 hose fittings, the old one had 2... So I am still confused on if I did this part right. The first and only time I took the boat out with the new fuel pump the boat ran perfectly never stalled once, it did however start leaking oil from the fitting around the fuel pump.
3. I have tried adjusting the idle, fuel air mixture, spark plugs seem good.

Attached I'll have some pictures I've taken of the engine that may help.My current thought is that the engine was not getting enough juice for the battery to handle the load, I had notice in the past that if I ran all the accesories the entire boat would cut out. I am redoing my boat with a 3 battery system regardless.

Any help or opinions would be awesome.


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so, short story is , i you squeeze the primer bulb every now and then, the boat runs great and has acted the same way with the original fuel pump, and a replacement fuel pump. ? is that correct?
That would work with the old fuel pump. The first time I had it out with the new fuel pump it didn’t need that but started leaking oil of the fitting also out of 2 of the hose connectors on the new fuel pump.
After you figure out the fuel pump, check the float level in the carb. I think the float might be too low and the engine is burning more gas at high rpm than can be replaced.

Sent from my SM-A526W using Tapatalk

First off......The primer bulb will never stay hard while the engine is running. The primer bulb is on the SUCTION side of the fuel pump. The only time the bulb will feel hard is when you pump enough volume into the fuel system to close the needle and seat and build pressure in the bulb.
Now.....we need be absolutely clear on you squeezing the primer bulb to keep the engine running at WOT. Are you absolutely 100% sure that worked each and every time you did it?
Except for the leak did the new fuel pump cure the issue? Am thinking not. Explain.
Your issue will not be with the charging system.........period. It is a limited amperage output system and is designed to run like that all day long if needed.
Lets get some accurate answers here before we throw darts at a board with troubleshooting.
When you pumped fuel to the motor using the primer bulb, you were doing the fuel pump's job. That tells me the fuel pump wasn't' doing it's job pumping fuel to the motor - bad fuel pump. At low idle, the fuel pump could keep up but it couldn't supply enough fuel to run the motor at higher RPMs.

I am confused about the fact that you changed the fuel pump and it worked after that.'s fixed?
So when I replaced the fuel pump it worked perfect the first time I ran it. It then started leaking but it still ran that first time. Then when I took it out the next time the same thing happened and the engine cut out.

Take a look at these. The first is the old fuel pump, the second is the new fuel pump. It is possible that I should have installed the new one differently. I’m not sure what to do with the other hose connectors.


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You have had the engine out two times with the new pump? One time it ran and the next time it did not? Did you pump the bulb the second time and have the engine go back to WOT? Please be clear on everything you makes a difference in the help we provide.
With the first pump were you able to continue to squeeze the bulb and make the engine run consistently as long as you were willing to squeeze ?
Also there is a difference in terminology just so you are aware. Starvation of fuel is normally seen as a surge not a cut out. A cut out is usually seen as the engine quitting.
Knapstacks89 said:
So when I replaced the fuel pump it worked perfect the first time I ran it. It then started leaking but it still ran that first time. Then when I took it out the next time the same thing happened and the engine cut out.

Take a look at these. The first is the old fuel pump, the second is the new fuel pump. It is possible that I should have installed the new one differently. I’m not sure what to do with the other hose connectors.

i think you got it backwards. isnt the second (bottom ) one the original? if i remember right, there is an oring that goes around a plunger on the engine side. the plunger is ran by the cam to operate the pump. that is probably where your oil leak is coming from.
what is the purpose of the extra hose nipples? the pump pictured mounted on your engine has a fuel line going into, and one going out of the pump. why does the new pump have extra nipples? wrong pump? or maybe yamaha changed the pump and it can accomodate two tanks? should you cap the unused two nipples?

considering the misinfo, the very first thing i would do id to confirm that you bought the correct pump.

the picture on the fische only shows the two nipples like your original pump, but the replacement has a superceded part number and shows two extra nipples

so, just block off the extra nipples. take the oring off the old pump and install it onto the new one, use a dab of grease to keep it in place.reference number 18 on the diagram.

oh, and when you go for a test, be sure and loosed your cap on the fuel tank to eliminate too much pressure building as i noted before.
How about fuel? Is the fuel good? I had a problem one time that was caused by bad fuel. I ran the motor the evening before going out and it ran fine. The next morning I bought fuel on the way to the ramp and after launching it would not run consistently. I took it home and after changing fuel it again it ran fine. The fuel I purchased that morning before launching was bad.
I had one of those motors that made me crazy. Turned out, it had TWO problems.... One was a cracked wire @ the ignition trigger. It would act up and then fix itself. Made me crazy until I caught it in the act by shaking the harness while running.

The second issue was the top seal under the flywheel. After that, the motor ran great.
Oh... And another very difficult one that sounded like yours ended up being a bad charging circuit and corrosion at the battery connection.

The motor wasn't charging properly, so it was firing off battery power. With the poor battery connection, when you ran it up, it missed and lost PRM like a starvation issue. The fuel system needed some tightening up, but in the end, it was a stator and trigger issue causing the main problem.

This is probably NOT your problem, (I honestly haven't read all the posts) but it may help you or someone else, if the fuel repairs don't solve the issue.

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