Bad Mercruiser Fuel Pump

[viper10000]

I'm not sure if many people had this problem or not, so I'm going to just give a little story here about an experience with a Mercruiser fuel pump. I have a 1993 Mercruiser 5.0LX 305 V-8 230HP. I was having a problem with fuel making its way into the oil. So, I learned that either the fuel pump needed to be replaced, or, the carburetor need to be rebuilt. Both of these parts were original from 1993. So, I replaced the fuel pump thinking that the ethanol in the fuel must have eaten away at the internal parts of the fuel pump. After replacing the pump with a mercruiser pump, the engine wasn't really running right and the carburetor was beginning to flood out. The carburetor is a Rochester quadrajet. So now that this was happening, I decided to rebuild the carb since it was all original. After rebuilding, the flooding problem in the carb was still occuring. I tried replacing the needle and seat and float again in the carb with it still flooding out. Then I purchased a rebuilt Quadrajet from a carb shop and was told that if this carb floods out then there is a problem with the fuel pump, and the quadrajet can only take 4-6 lbs of pressure and anything more than that would force the needle open. So, I replaced the carb and still had it flooding. Now I called Mercruiser to que them in on the situation. After I explained to them what had been going on, they said to try a thicker gasket, part # 27-431861. After this gasket was installed, the flooding did stop. However, a few minutes after running the engine, a ticking noise presented itself. This had to be the rod that pumps the fuel pump slapping against the pump or the cam inside the engine since the pump was now about 3/16 of an inch further out from the block. Now another phone call to Mercruiser to find out that "if after using gasket 27-431861, the flooding does not stop, or a ticking noise occurs, then you must use an aftermarket fuel pump." So, now I bought a Sierra fuel pump, part # 18-7283, bolted it on, and had no problems since. Just thought I would try to spread the word if anyone else was having this problem. Any questions, please dont hesitate to ask!

[Pete104]

The bottom line is that you used the "aftermarket" pump with a thin gasket? Are you stuck with an extra carb now?

Great post!! Great info!

[Sea Honky]

hay have same problem just decided to replace pump on 89 454 mercruiser original and thats when flooding problem started also bought mercruiser pump and know have to go with sierra did you use thinner gasket with sierra i to bought rebuilt carb twice and still flooding what is up with mercruiser pumps ? thanks missing out on salmon season because of this pump !

[viper10000]

Unfortunitely, I am stuck with the remanufactured carb. It was only $279 plus tax and a $75 core deposit which I'm working on getting back. And yes, I used the aftermarket Sierra pump with the thin supplied gasket. The weirdest thing is that the people at Mercruiser told me to use the aftermarket pump. They said that if the thick gasket I used did not fix the flooding problem or if a tapping noise occurs, then I need to use an aftermarket pump. Very strange that I can't use a Mercruiser fuel pump on a Mercruiser engine!

[HT32BSX115]

Howdy,

I replaced the fuel pump on my Bravo Raw water pump mount when I installed the engine in my current boat (see Signature below)

I went to Autozone and bought an AIRTEX (AKA Master) marine pump for something like $55.

http://www.airtexproducts.com/

Before I bought the pump, I called AIRTEX and asked them about the pump they produce for Mercury Marine.

They told me that they are the OEM manufacturer for Mercury and MANY other companies.

It appears that regardless of where you buy it, it was probably built by AIRTEX.


Now, having said all that, if you didn't put s small (0-15psi) pressure gage on the output of the pump while it was running, you REALLY don't know if your problem was excessive pressure, a defective pump or a crummy carb rebuild. (If I got excessive pressure in a mechanical pump, I would just "adjust" the arm on the pump until I got the pressure I wanted!!......this ain't electrical engineering!!!)

Just replacing parts and hoping for the best is usually a poor way of fixing a problem......


Just saying.....


Regards,


Rick

[viper10000]

Yeah, I did end up putting a pressure gauge on the pump and saw that I was getting too much pressure. Thats when I called Mercruiser and they initially told me to try the thicker gasket in order to change the stroke on the pump. There is no other way to adjust this pump. The Sierra pump is made by teleflex marine (according to the box).

[fishrdan]

Use a thick gasket to adjust the fuel pump's pressure,,, WH*! You shouldn't need to do that, unless they pump is screwed up.

The pump has pressure relief springs that should trim the pressure to the proper PSI. If the springs are too stiff and let too much pressure build up, it's a fault of the pump, not the installation or gasket thickness.

I suspect that Mercruiser suggesting to use a "thick gasket", is easier than warrantying bad pumps.

[viper10000]

It very well could have been a defective pump. But for Mercruiser to say "use an aftermarket pump" was shocking to me. The gasket that they had originally recommended was just about 3/16 inch thick. After trying that gasket, the flooding problem did stop. But then the ticking noise started. I guess that 3/16 inch difference was enough to cause extra play in that push rod somewhere. But anyway, the boat is running great now! I wish I went aftermarket with the fuel pump from the start but who would've known that this would have caused this issue.

[ipete6]

is this what the flooding sounded like? Mercruiser 3.0 stalling problem - YouTube

[Don S]

This thread is 2 years old ipete. Did you miss the red warning bar ????????

[viper10000]

No the engine ran flawlessly. The flooding was actually fuel overflowing from the carb and running all over the top of the engine.