Fuel Pump problem?

[jg5343]

2003 Mercruiser 350 MPI Horizon OM643971
Bravo One outdrive OM185090

I recently reported a loss of power in another thread but since the swap over have been unable to locate that thread to add to it. The power loss was mainly a hole shot problem as the top end is about the same. Maybe 100-200 rpms less and 2 mph. Not a big deal there, but the low end is fairly weak and caused me to start trying new props. There were no codes found, and the mech said he sees nothing apparently wrong with it. I felt the same way until a few days ago.

At the rinse/wash down station I turned the key to on to wait for the fuel line to pressurize. There was no sound of the pump and after a few seconds I got an alarm tone. After turning the key on and off about 6 times and the same with the battery, I finally got it to charge the line. It worked fine after that. Yesterday we had it on the water and it ran fine, power loss still there, but very usable. If you had never driven the boat, you may not have even noticed the loss. Anyway, back at the rinse down I get the same problem solved by the same solution. This has happened before but had been a few weeks and hadn't done it since. Now I get it two times in a row, and ONLY at the rinse station. I checked that all the electrical connectors are solid and intact.

1. Could this be my power loss problem?
2. Is there an easy fix for this?
3. Any ideas as to what only causes it to happen out of the water? (Yes, there is water flowing to the engine, and it does draw it in once started)
4. Is there a computer that runs all this stuff like in your car?
5. The drain plug leaked (never trust the wife to do anything) right before all of this started and filled the bilge up to the auto bilge level. Might have put the bottom couple of inches of the engine in the water. Anything down there that could cause any of this? (I changed the oil immediately just in case)

Thanks for all the help, you guys are always awesome.

Jimmy

 

[jg5343]

Here is my original post:

Here is my original post:

The rpm and mph loss has slowly worked its way back to almost normal since this post 3 weeks ago. But this is the history:




""Motor is brand new in 2003, Bravo drive, 23 pitch prop.

Had the boat out twice last week on the bay and all was great. Took it to the lake Sat and it now seems as if it is running at about 3/4 throttle. My hole shot is crap. Takes 30 second to get on plane and once on plane I have lost about 3-500 RPMs. Used to run at 48-5000 now its around 4600 WOT with about a 5 mph loss as well.

I have replaced the fuel filters, put gas treament in and ran 93 octane through it. Helped slightly, but no significant difference. I checked the linkage for the throttle and it has not slipped. Checked the prop for line/fouling. Nothing. Plugs new this year.

Motor response is great, sounds good, nothing at all unusual except the loss in torque/RPMs/speed. I am still able to use the boat, and can cruise at normal speeds after I let it work itself up to being on plane. This motor has been babied and there are no visual signs of wear. Any clue what could all of the sudden be causing this problem? BTW, same gas was in it through out, until the problem happened, then I put the treament in with 93 octane. It ran awesome on the same gas it ran crappy on. Thanks for the help. ""

 

[tystick]

Re: Fuel Pump problem?

what prop are you using?

 

[bigbrownbuku]

Re: Fuel Pump problem?

you mentioned no codes. thats a start.
check the other basics, fuel rail pressure (at all rpm), battery connections(both ends). next pull your relay's and check the pins. also pull the pump plug and check the pins. check your main harness is properly seated with a s/s band clamp holding it in place.

 

[Reel Poor]

Re: Fuel Pump problem?

You need to check fuel pressure on your low and high pressure fuel pumps, and fuel vaccum test between fuel tank and low pressure pump.

 

[jg5343]

Re: Fuel Pump problem?

Thanks for the replies.

The prop question is not relevent since I had no problems before this started. Its a 3 blade 15x23 on a Maxum 2300SCR 23' ~4500lbs dry. I have experimented with some props since it started and found that a 21 pitch gives me the best over all, but the 23 is still best cruise. We'll see after its fixed, but all advice is welcomed.

All the connectors look fantastic. Had it out today and it did the same thing, this time on the water. First time for that. We stopped at Snoopy's to get ice cream, came back and it would not charge the fuel line. Then did it again at the rinse down. Otherwise ran fine, except the hole shot of course. I figured out that all I needed to do is unplug the fuel pump and then plug it back in to get it to work. This worked 3 out of 4 times I tried it.

I am almost 100% sure there will be a code now since there is an aural tone every time this happens so I believe I have done all that I can. Its still under warranty for another 3 weeks, lucky me, huh? So I am taking it to the shop tomorrow and letting them deal with it.

I would still appreciate any opinions you all have on what it could be.

 

[jg5343]

Re: Fuel Pump problem?

Ok, got it back from the shop. All the codes show normal stuff, but the fuel pump problem was caused by a relay that was sticking. That's fixed. Now the power problem is still there. The hole shot is crappy and to hold it on plane is a chore, once I get below a certain rpm it starts a downward spiral to being nose up. Then I have to start all over like I am in the hole even though we are still doing 10 mph (i. e. trim tabs full down, outdrive trim full down even though it is never far from full down anyway). What could be causing this problem? Could there be something in the outdrive? When I rotate the prop by hand I hear that winding sound common with what a car sounds like in reverse. Is that normal? The mech thinks it might be the computer itself, but I feel like the engine is running smooth. Ideas?

 

[Reel Poor]

Re: Fuel Pump problem?

Here is an outline, courtsey of DonS