Merc 1993 60hp 3 cyl. wont go past 3000 rpm... FINAL UPDATE!

[akwalker]

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... UPDATE

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... UPDATE

I guess its easy enough to rebuild the fuel pump (again!) and see if that takes care of it. Hopefully it will, but here's what I worry about with the pumping the fuel bulb theory:

Squeezing the primer bulb is reletive to the person's grip strength. If you squeeze the bulb "hard", you are introducing alot more than 7-10 psi of fuel pressure at the carb inlet, so effectivly what happens is you blow the inlet needles off thier seats and overfill the fuel bowls. This fuel needs some place to go, which is right out the bowl vent. In a running engine, the fuel is drawn into the engine instead of dripping out the carb opening. The engine now gets a shot of extra fuel, and the RPM's temperarily increase. Because of this, Im not sure that squeezing the primer bulb is an accurate test, in your case. The reason I say this is because you are complaining of a varience in engine speed from about 5k RPM to 4K RPM. I'm starting to think that the low compression on that one cylinder is the basis of your problem. Hopefully it isn't, and re-rebuilding the fuel pump will cure it. Best of luck.

 

[saumon]

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... UPDATE

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... UPDATE

Hopefully it isn't, and re-rebuilding the fuel pump will cure it. Best of luck.

That's what i hope. I'll receive the kit in the next days then redo the pump, do a lake test and give you an update.

One more question, if you guys don't mind: inside the pump, there is 2 rubber disk (non-replaceable) on top of wich the plastic discs goes. These 2 rubber disk were not absolutely flats: on their sides that face the pump body they have some "bumps" in the rubber that fit into the pump body hole. Does these "bumps" were on the discs right from the factory or they were created by the pump pressure, and am i better to put them in the same place or to flip them so the flat side now lie on the pump body to have a better seal (on my first rebuild i put them as they were before)?

 

[akwalker]

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... UPDATE

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... UPDATE

Hopefully it isn't, and re-rebuilding the fuel pump will cure it. Best of luck.

That's what i hope. I'll receive the kit in the next days then redo the pump, do a lake test and give you an update.

One more question, if you guys don't mind: inside the pump, there is 2 rubber disk (non-replaceable) on top of wich the plastic discs goes. These 2 rubber disk were not absolutely flats: on their sides that face the pump body they have some "bumps" in the rubber that fit into the pump body hole. Does these "bumps" were on the discs right from the factory or they were created by the pump pressure, and am i better to put them in the same place or to flip them so the flat side now lie on the pump body to have a better seal (on my first rebuild i put them as they were before)?

Put it together like it was

 

[akwalker]

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... UPDATE

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... UPDATE

Saumon, any luck on this?

 

[saumon]

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... UPDATE

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... UPDATE

Parts not received yet. I'll do the rebuilt monday or tuesday and test it on the water. I'll keep you informed.

 

[saumon]

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... FINAL UPDATE!

Finally, everything is now fine. I'll do my best to explain you what happened (remember that english wasn't my native language).

At first my WOT rpm drop to 3000, so i change the inline filter, clean the carbs and rebuilt the fuel pump and, after all this, the engine run a bit better, let's say around 4000, but not close to 5500 until i squeeze the primer bulb. And the culprit was, at last, ...a kinked hose.

Let me explain: when i first replace the inline filter, i put a generic glass filter with removeable cartridge, but it was longer than the original, so i had to cut the hose a inch or so. As the problem was not totally solved (goes to 4000 rpm), i think that this filter could cause a restriction so i bought an OEM one but the hose was now too short. I then replace the hose between the pump and the filter with a generic automotive type 5/16" fuel hose, but this hose had to do a 90 degreee bent and this produce a kink in the hose, causing the restriction.

If it could help some other peoples, here's two important things i learn from this:

1- when you troubleshoot a system, do it one step at time. In this particular case, i've tried to save time by doing the fuel pump, the carbs and the filter all at once but i still doesn't know what was the culprit (probably the fuel pump) and it caused more problem. If i had only do the pump first, there's no chance that i have messed the filter and hose, thus causing a second problem.
2- always use OEM parts. I first bought an aftermarket filter at 10$ then ended by buying a Merc one at 13$, so it cost me 23$. I've also used automotive fuel hose that caused another problem then replace it with a 4$ OEM one with a built-in 90 degree bend that solved the problem. So, don't buy aftermarket parts, they will cost you a lot of money and time.

Hope it will helps some in the future. Lessons learned for me, and thanks to all of you guys who help me!

 

[akwalker]

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... FINAL UPDATE!

Wow, so simple. Glad you found and fixed the problem.

 

[Texasmark]

Re: Merc 1993 60hp 3 cyl. wont go past 3000 rpm... FINAL UPDATE!

Totally agree on one thing at a time. But when doing an overhaul, it's a cross your fingers thing and hope for the best.

Glad you got her fixed.

Mark