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40 hp evinrude idles but splutters under load

A

Andrew and Hamish

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Motor was over heating replaced water pump,impeller thermostat, took head off replaced head gasket as water in top cylinder,torqued head back on to specs. Done compression test 125 both cylinders,new plugs,cleaned carbies with lots of help from here.

Motor starts and runs easy, engine warm, idles on two cylinders. Pumps plenty of water. But when put into gear and throttled up it starts spluttering going from one to two cylinders ,reving up and down without touching control once in gear. At idle can remove either plug lead and motor still idles ok. All done on earmuffs.

Tried early on in bay motor idles good but when put under load in gear it struggles to go feels like it running on one cylinder I could row faster.

Could it be the coil or something electrical causeing problem. Also checked plugs they were dry.
Can anyone help once again.Cheers Andrew.
 
1987 40 hp evinrude

Both carbs open at same time, Both fully open when throttled all the way.Has plenty of spark. What does WOT mean as it was said to me in a reply about carbs?
 
I never touched any thing to do with timing .Only took controls cables off engine to get to bolts that hold on engine cover . So I could undo head bolts. Done repairs and put it all back together. Engine was running good but was hot so changed out thermo etc. Cant understand why it runs like this now as it was a water problem not fuel or electrical before??
 
1987 40hp...... The brass high speed jet, located in the bottom center portion of the float chamber way in back of the drain screw/plug, if slightly fouled, clogged, gummed, would cause the engine to hesitate and/or die out when the throttle is applied... BUT... this does not appear to be your complaint.

The rpm of the engine at idle increasing and decreasing on its own is normally caused by having the throttle butterfly linkage between the carburetors sightly too tight... resulting in one butterfly completely closed and the other ever so slightly open. Double check that linkage... easy to spot a misadjustment simply by disconnecting the linkage from one of the carburetors.
 
Done compression test on stone cold motor it was 125 both cylinders. As for fuel I noticed fuel filter sits upside down on my engine and is only got about one fifth of fuel in it at any time could I have put it back in wrong way up as it only seems to fit this way?
 
done cylinder drop engine keeps running with either plug pulled off.It will start and run on one cylinder but only the bottom one. if I take off top plug wire it wont start. this was done while engine at idle.
 
If I take top plug lead off, engine will start and run on bottom cylinder only. But it will not start if I take off bottom plug lead. When engine is running I can take top plug lead off and engine still runs on bottom cylinder ,also can take bottom plug lead off and engine still runs on top cylinder . Is that a cylinder drop test. Have tried changing plugs top to bottom it makes know difference to outcome?
 
Will try fuel in top cylinder today with bottom plug wire off,to see if it will start.Engine has pulse pump and I premix all fuel. VRO was disconnected way before I bought boat. Also never touched fuel pump only removed fuel filter to check and it was clean.
 
Took out new sparkplugs and put back old ones, engine will now start and run on top cylinder with bottom plug wire off / and start and run on bottom plug with top plug lead off?But still wont run normal when you put it into gear. Once in gear and throttle pushed forward engine should rev faster as you push throttle, but my engine slowly gets faster,peaks out slows down peaks and splutters over and over, doing this with throttle in same position. What now im getting confused.
 
Have you checked the fuel pump diaphragm as suggested here.----Advice based on many years of experience and a " no cost " inspection step.
 
Started engine put into gear throttled down control motor splutters.but when I continualy keep squeezing pulse pump motor peaks and stays at revs running well, stop pumping and it splutters again. Will order fuel pump kit . See how it goes then. thanks for all the help. Will post resuts.
 
Hello there,
1987 40 hp evinrude bought a fuel pump kit #398514, as it said on this site for my outboard. Pulled pump apart this kit looks nothing like the kit inside of my fuel pump.My fuel pump has a number on it 174570,two diaphrams one 55mm across,one 60mm across 5 holes in each for screws. Diaphrams look good.There is 3 wires coming out the bottom of pump. Is this an electrical fuel pump??.Connect wires to power should it start clicking? as nothing happens when this is done. engine splutters under load but idles good. Pump pulse ball fuel filter fills up full engine runs good under load , stop pumping ball and filter drops back to under third engine splutters no power.What now ???
 
Yes I am premixing the fuel.What does VRO mean? if diaphragm is good on my pump what is causing spluttering under load then?Do I have to get a fuel pump the same as I already have ? if so why If mine seems ok.
 
Will purchase a 3 port pump and fit it to engine.Is this a hard job or is it straight forward.Is there a website i can view that shows you how to do it.It will take a week to get pump. I hope this fixs outboard. thank you.
 
Order a pump ( 2 screws and a gasket as well) for a 48 HP model like yours.---------There is a place to neatly mount it on the side of the top cylinder.--------Find the 2 screw holes and remove the pulse port plug between them.-------Remove the VRO pump and plug the pulse port for it.-------Hook up some new hoses to the new pump.
 
Shouldn't I get a two port pulse fuel pump as it has a pulse hole at the back of pump to fit into hole on engine block? It pulses from back of pump, leaves one port for fuel in and one port for fuel out? Is this correct? Do I still need a fuel filter on fuel in line for this fuel pump? Cheers Andrew.
 
The proper fuel pump for your motor has 2 hoses and the pulse port does not have a hose.---------It is bolted to the side of the top cylinder as explained before in post # 31-----It uses a gasket to seal the pulse port between the pump and the block.
 
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