2003 Mercury 2.5l 200hp EFI Motor Loss of RPM at WOT ??

[Coxwain]

2003 Mercury 2.5l 200hp EFI

OT749297

2003 Mercury 2.5l EFI 200HP

Not easy to upload photos, please click link for video of RPM drop on WOT
https://photos.app.goo.gl/L5J7jhUHQKr1HXhA6
https://photos.app.goo.gl/L5J7jhUHQKr1HXhA6

I bought this boat in April, have rebuild the engine, but have been plagued with no power, low rpm and now fluctuating RPM at WOT.

I took it out earlier this week and kept getting this RPM drop after getting up on plane and WOT for a few seconds. I went back, read some more on the forums, and I had a 2 battery in parallel? 12v for cranking and accessories. I separated the two batteries so that the cranking is only connected to the motor and the accessories are connected to the other battery.

also, went out on the lake and had the same problem as before. This time, I tried to pump the bulb and it was soft, took approx 5-10 pumps till hard. then it would run great, WOT no problem. after a while I would drop RPM again, so I would stop and reprime the bulb and it would work great.

just before I got into the dock, while in gear, with no signs of dropping RPM at WOT previous to coming into dock, I pumped the bulb and it took 5-7 pumps to firm.

sounds like its one of the fuel pumps. Which one? Could it be something else? Fuel lines? I noticed primer bulb was sierra.

Any thoughts?

[EuropeanAM]

Very likely a fuel supply problem. Suggest starting with ALL items listed in the following thread, use only the recommended components, and do all at the same time:

FUEL LINES AND PERFORMANCE PROBLEMS

[Coxwain]

Okay, good thread for sure. Here is the summary of what to do.
Line from tank to the bulb
-Bulb
-Line from Bulb ALL THE WAY TO FUEL PUMP INSIDE COWLING
-Rebuild Pulse Fuel Pump (I dont have any idea on how to do this?)
-Replace Fuel Filter and remove ANY debris in the filter chamber.

Are there any instructions on how to rebuild the pulse pump?
Also, I have an R91, how do I remove the seats?

The fuel line that goes into the engine compartment, is that straightforward to replace? There doesn't seem to be a lot of room to manuver?

Also, can i run 5/16 hose from tank to bulb? or does it have to be 3/8"

[leonreno]

When you buy the Mercury Pulse pump rebuild kit it includes the instructions on how to do it.

when I replaced the fuel line in my boat I bought a splice connector and used the old line to pull the new line through.

[Coxwain]

when I replaced the fuel line in my boat I bought a splice connector and used the old line to pull the new line through.

That is a good idea, but how do you know the measurement to purchase?

[EuropeanAM]

You will need to measure the line yourself, or measure along the estimated pathway it travels.

Alternative is to pull a leader-wire (or rope) through with the old fuel line, so you have something to pull the new line in with.

[Coxwain]

OK. I pulled off my seat and looked in the back
From tank to primer bulb (Sierra bulb) looks like 3/8" hose with red letter
From bulb to inside housing, 3/8" black with grey / white letters / font

Should I be tank----3/8"-----bulb-----5/16"----motor?

[EuropeanAM]

Yes sir- that's correct (as per the link above).

[Coxwain]

what is the model # of the bulb and the 5/16" hose
I think I will change bulb and hose from bulb right now.
change the hose from the fuel tank when I have some more time.

[EuropeanAM]

8M0061875 or 8M0061876 for the bulb.

The gray 5/16" line comes in 100' rolls... so unless you want that much, better simply buy the bulk length from a dealer that carries it.

[Coxwain]

5/16" is grey? I thought black

What rating?

[Coxwain]

Also why is there 3/8" from bulb to motor now? Black

[Coxwain]

I ended up getting a1-15 black both 3/8 +5/16

[EuropeanAM]

Incorrect. READ INFO IN LINK- do it right the first time!

FUEL LINES AND PERFORMANCE PROBLEMS

[Coxwain]

-Tank to Primer Bulb (3/8" A1-15 Line)
-Primer bulb to Fuel Pump inside cowling (5/16" B1-15 line).

A1-15 is better?

"Recommended replacement line: Mercury or Quicksilver "EPA APPROVED" Line. This line is available in BULK lengths, either 5/16" or 3/8" Inside Diameter (we try to always keep plenty in stock). The NEW, EPA APPROVED line is GRAY, with BLUE PRINT on the line.

We now also carry A1-15 Low-Permeation line for below-deck installation.

3/8" Line from TANK TO BULB, and 5/16" Line from BULB TO FUEL PUMP INSIDE COWLING (normal installations)."

Its not super clear if you are to use A1-15 black or grey. I wonder if you could fixt the first page of this thread to show the current bulb parts as well as the hose specs. I had to go through 6 pages to get to the suggestions of hose. Still not sure why the grey is recommended out the outside with the lower grade hose?

[SilverFox579]

The recommended replacement fuel hose in the link is Mercury or Quicksilver brand and is gray (some call it silver) with blue lettering. The correct diameter is 3/8" from tank to bulb and 5/16" from bulb to engine. You can obtain A1-15 from other sources and color will vary. I chose to use Mercury branded fuel hose when I replaced the non-EPA approved fuel lines in my boat.

[Coxwain]

well, i missunderstood the guidlines and purchased a1-15 black from a mercury dealer

job is finished, went pretty smooth, the biggest problem is getting the hose over the barb fitting, luckily i have a wirsboro tool that spreads the end of the hose that was a big help.


primer bulb is firm now and has the mercury bulb.

hopefully I can get out on the watter to see if that fixed any of the issues i was having. I doubt it as the hose seems like it was in pretty good shape.

[leonreno]

My boat/motor came with the black line so that’s what I replaced it with, black A1-15. The 16 year old line looked pretty good after pulling it but I replaced it anyway. You should be ok.

[SilverFox579]

Ensuring it was A1-15 was the important part. Don't have a Wirsbo tool (brother who lives 300mi away does), but a little oil (or spit) and a clean, tapered end pry bar works fine too. Of course, can always follow Don's recommendation and dip hose end in hot water for 10 secs or so, shake water off, then install.

[Coxwain]

Looks like the fuel lines weren't the issue. Took it for a water test today. The big difference now is that I can't get to full rpm power , max rpm arou 4-5k then drops and pumping the bulb doesn't make any difference. I didn't get it to 5800 rpm ever

next is fuel gaskets?