Loosing power

hey all

l have a issue that's developed with my 60 merc and i hope some one may have a suggestion on a fix .the outboard starts easy as every time hot or cold idles sweet and excelerates fine BUT after running WOT for a few minutes the revs die off to approx 2400 rpm .if I stop and let it idle for a while it will come good

 

 

 


Walfootrot's picture

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Date Joined: 23/07/12

sounds like a fuel issue, is

Sat, 2016-04-23 11:56

sounds like a fuel issue, is it overheating?

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More drum lines, kill the bloody sharks!

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fuel pump mate

Sat, 2016-04-23 12:10

 .

Posts: 388

Date Joined: 28/12/12

 Shit fuel/blocked filter be

Sat, 2016-04-23 12:32

 Shit fuel/blocked filter be my guess mate had the same problem changed the main filter n fixed the issue

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 Pgfc member

Posts: 54

Date Joined: 21/09/11

Loosing poweer

Sat, 2016-04-23 13:06

ive changendthe fuel filter and it didn't make any difference.Is there a check that can be done to n the feel pump or is it a matter of a new pump kit and give it a try 

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Date Joined: 04/04/13

fuel pump

Sat, 2016-04-23 13:49

Tough to do that as it is powered bt the motor and visa versa.

In any case merc workshop manuals (that I have seen) recommend replacing

the diaphrams if the pump is disasembled. A kit is cheap.

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Crack in the head?

Sat, 2016-04-23 13:49

 Crack in the head opeing up unde rheat?

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Date Joined: 15/09/15

we had a similar drama and

Sat, 2016-04-23 13:51

we had a similar drama and replaced a diaphragm, can't remember what it was exactly for but ran fine after that

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Date Joined: 04/04/13

fuel pump

Sat, 2016-04-23 13:53

Tough to do that as it is powered bt the motor and visa versa.

You could try to see if revs increase by hand priming while you work the throttle

armature i suppose.

In any case merc workshop manuals (that I have seen) recommend replacing

the diaphrams if the pump is disasembled. A kit is cheap.

Posts: 54

Date Joined: 21/09/11

Loosing powerlike i

Sat, 2016-04-23 14:23

 Thanks gents

 

looks like I'll get a kit for the pump and see how that goes I'll let you know the out come

 

cheers

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Date Joined: 18/01/12

 jeez, if there is one thing

Sat, 2016-04-23 15:40

 jeez, if there is one thing Ive learnt as an engineer, it is

ALWAYS START WITH THE EASY AND OBVIOUS SHIT

Start by checking for a kinked fuel line.
When the revs die off, feel the bulb, if it is sucked down your problem is before there, if it isnt it is past there
Squeeze the bulb up when the revs die off, that will tell you if its a fuel issue or not.

If squeezing/pumping up the bulb makes no difference when its playing up then it likely isnt the pump.
As it dies off, is it missing or smooth but just losing power?

AFTER doing the shit above then look deeper

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pricey10's picture

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 amen to starting with the

Sat, 2016-04-23 16:29

 amen to starting with the easiest most obvious stuff.

Was just in exy and watched these guys try and get there boat going for 2 days. After a few beers we thought we better go help them. Turns out there kill switch was un plugged

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LOL

Sat, 2016-04-23 17:08

Gold.

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jighead's picture

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Bloody engineers

Sat, 2016-04-23 19:02

 Everybody bow down.

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funny

Sat, 2016-04-23 22:26

 listen and learn son, or just keep your head up your ass, your choice 

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 Give a man a mask, and he'll show you his true face...

 

 

The older you get the more you realize that no one has a f++king clue what they're doing.

Everyone's just winging it.

 

scano's picture

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Date Joined: 31/05/07

My educated guess would be

Sat, 2016-04-23 15:48

 Problems with the fuel tank breather. If air cannot get into the top of the tank, the fuel flow will become restricted to the point it runs like crap.

seen it plenty of times with buses and trucks also.

 

if it starts to run bad after wide open throttle then undo the fuel filler cap and see if that makes any difference. If you hear air hissing when you crack the seal of the fuel filler cap you know you have a breather issue.

 

scano

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Krusty's picture

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Date Joined: 27/11/15

 Do exactly what Rob H has

Sat, 2016-04-23 16:24

 Do exactly what Rob H has suggested....start with the absolute basics first and one by one eliminate areas until you find the problem.

The fuel tank breather is a good start like scano said and work from there.

It can and will more than likely prevent you from chasing your tail and becomming confused and spending your hard earned on parts you are "guessing"  could be the problem 

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My fishing spots are so secret........... even the fish don't know where they are !!

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fuel problem: easy + obvious

Sat, 2016-04-23 17:15

 Rob h is correct. Its so obvious tho that I struggle to imagine anyone

posting this if the priming bulb is not firm to start with.

Therefore my  money's still on the pump. We'll see.

 

Krusty's picture

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Date Joined: 27/11/15

The priming bulb will be firm

Sat, 2016-04-23 17:33

The priming bulb will be firm before starting after priming but it won't stay that way once the engine is running as it has done it's job and "primed" the fuel line to the pump at the  engine.

Once the engine is started It then just becomes part of the fuel delivery line, there will be no pressure there at all as it effectively becomes part of a sucsion line.

That is why Rob suggests to check it because if there is a vent problem or blockage before here then the bulb will collapse on itself as the pump is trying to suck the fuel through a restricted line. Just one of the first easy quick steps to take.

You may just be right but it pays to use the process of elimination and start with the basics.

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My fishing spots are so secret........... even the fish don't know where they are !!

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fuel

Sat, 2016-04-23 17:42

 Ok I should have written ' cant beleive someone would post this if the bulb is not 

firm to start with or if the bulb is collapsed during running or if the fuel line from the pump 

is disconnected and there is fuel going everywhere or ... '

Where does it end ? There is a certain level of competency

required to not be dangerous to other people.

Anyway that's more than enough from me on this one.

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Date Joined: 18/01/12

 Certainly dont want to upset

Sat, 2016-04-23 17:44

 Certainly dont want to upset anyone but it scares me how often on here, when someone asks "my outboard wont start" and people suggest straight away a fix that involves spreading it all over the floor after waiting a month for parts to arrive!
Even for an experienced mechanic, as soon as you start undoing bolts you are introducing more factors ($$$ and complications) into the equation.

Besides the egg on face factor when ya missus walks up and asks "whats that wire hanging there?"

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 Give a man a mask, and he'll show you his true face...

 

 

The older you get the more you realize that no one has a f++king clue what they're doing.

Everyone's just winging it.

 

Y_Knot's picture

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Date Joined: 05/11/10

agree with Rob H

Sat, 2016-04-23 19:47

 it could also be sucking air from fuel delivery system, loose hose clamp, small hole...... 

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Date Joined: 18/01/12

 could be but that would

Sat, 2016-04-23 22:40

 could be but that would likely show up straight away.
I would have thought that a damaged diaphram in the pump would show up pretty quickly also as it wouldnt get fuel pressure up for running under load, but not certain of the quirks in that

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 Give a man a mask, and he'll show you his true face...

 

 

The older you get the more you realize that no one has a f++king clue what they're doing.

Everyone's just winging it.

 

Posts: 215

Date Joined: 04/04/13

fuel again

Mon, 2016-04-25 08:38

 Second thoughts, if it's getting to and holding full revs at WOT it's probably not fuel.

Its probably electrical and I am thinking CDM or stator.

hornet42's picture

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Date Joined: 24/07/12

Fuel line

Mon, 2016-04-25 06:13

may have a kink in the fuel line after a service we have found one before  

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Scotte's picture

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 Is it running portable tanks

Mon, 2016-04-25 17:08

 Is it running portable tanks and is the breathers opening fully?thats first thing id check!

Krusty's picture

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Date Joined: 27/11/15

Definitely a fuel problem !

Mon, 2016-04-25 18:18

Going by the information on how the engine is performing it is definitely a fuel problem.

It's Either a blocked or restricted air vent, kinked or split fuel line, loose or cracked fuel fitting, (You have changed the fuel filters so you can rule out that), or even an old hose that has collapsed internally restricting the flow, it could be the fuel pump, which has been mentioned ....somewhere in your fuel system is a restriction, an air leak or reduced pressure causing the starvation of fuel !!

How old is the engine ? Does it have carburetors or fuel injected ?

Because it runs for a few mins at WOT then drops revs and settles at approx 2400rpm. Then after a few minutes idling is ok again..... it is definitely starving of fuel somewhere.

Just eliminate the basics first then move to the more complicated ....the problem will stare you in the face !!  

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My fishing spots are so secret........... even the fish don't know where they are !!

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Date Joined: 18/01/12

 

Mon, 2016-04-25 19:09

 

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 Give a man a mask, and he'll show you his true face...

 

 

The older you get the more you realize that no one has a f++king clue what they're doing.

Everyone's just winging it.