My 3.0 mercruiser sucks

[panterafuy]

hello all, new to this site and prettymuch boating in gereral.

my question is about my 88 merc 3.0L, stumbled last year, but all in all ran well enough to not worry. i winterized it last year and all was well, so i thought. this year i havent gotten the thing to run without spitting, misfireing or backfiring. all was replaced per summerization standards, plugs, cap, rotor, condensor, cleaned the points, and took the carb apart and cleaned it, also changed the oil (witch did have some water in it, mmm chocolate shake). after doing all this the thing still ran horribly, so i started to dig deeper, pulled the valve cover and found no play in any springs or in the pushrods. further down i found a head gasket that looked cooked, but i guess it was just dirty, cus theyre all aluminum on these. before i took the head off i did check compression, all good. anyway...what im gettin at is, why the hell doesnt my boat run right? it sounds like a timing issue, but i checked that too, it says 6 deg btdc, but doing it by ear, i found it between 12-20, at 6 it barley runs, someone please help, or point me to someone or somewhere where i can get some info and get this thing into the water before winter gets here again.

 

[WillyBWright]

Re: My 3.0 mercruiser sucks

Your timing is way too advanced. I retard 2 degrees from spec to 4 btdc to account for today's poorer fuel. If you can't get it to run there, I'd have another look at the carb or make sure the dewll is correct.

But my guess is that you need a new set of points. If the key had ever been left on, the spring heats up and loses spingyness. Don't get car points. They don't hold up worth a darn. You need good quality marine points with the nut for the connections. El-cheapo clip-ons just plain don't work at the kind of RPMs a boat motor turns. Make sure you put a dab of grease on the rubbing block or it will melt, and before you know it you lose your gap.

 

[CPro]

Re: My 3.0 mercruiser sucks

Not to hijack your thread...but I have a very similar problem...but with a '97 Mercruiser 3.0 LX.

I've replaced almost everything on the ignition system with the exception of the pickup coil. I've also done plugs, wires, distributor cap & rotor, fuel filter at the carb, fuel filter at the fuel pump. I also rebuilt the carb. Along the way, I siphoned off the gas tank a couple times and now have as clean of a fuel system as the boat has probably had for a while..

I'm going to put a fuel pump in it tomorrow...if that doesn't work I'm pretty much at the end of what I'm going to do to the boat. If & when it gets fixed I will be sure to let you know what it was!!!

 

[DHPMARINE]

Re: My 3.0 mercruiser sucks

Just a few ideas. The tune up kit for your engine is less than $20.00.that's new points,condenser and rotor.Don't ever bother to 'clean' points again.Start new.

Point gap = dwell = timing. If the gap is off,the dwell is off (duration of points open/closed) and the timing is off.The timing light can't correct this.Start with new points.A whole kit.

Also something makes want to wonder what a fuel sample from your tank looks like.Just a hunch.

DHP

 

[Bt Doctur]

Re: My 3.0 mercruiser sucks

"runs rough ,water in the oil" could the riser be dropping water into #4 cylinder?

 

[panterafuy]

Re: My 3.0 mercruiser sucks

good advice, thanks, the only thing i didnt replace was the points, theyre cheap so ill do it, but i think the water is more of a condensation problem, cus i put it in the water with fresh oil at the begining of this year, with the problems, it ran like **** and had no power, but i was out with it running in the water for at least an hour, with no water in the oil. so besides the points, is there anything else anyone might have seen that could explain it? i got good fuel in all cyl, along with good spark, and good compression, i got an odd issue, and i would love some help before i start pulling out more parts and dumping more money in.

 

[panterafuy]

Re: My 3.0 mercruiser sucks

also i spent several hours with it running with muffs on it in my driveway, with no water in the oil.

 

[Haut Medoc]

Re: My 3.0 mercruiser sucks

What was the condition of the plugs & how old is the manifold & riser?.....​

 

[panterafuy]

Re: My 3.0 mercruiser sucks

by riser you mean..............

 

[tystick]

Re: My 3.0 mercruiser sucks

I think DHPMARINE is right on with the real issue which is fuel supply

did you check the filter and or tank ?

 

[Bondo]

Re: My 3.0 mercruiser sucks

Ayuh,........

It Sure Sounds like a Fuel Delivery Issue..............

And I'm Betting that your Carb might be Junk.............

 

[Boatin Bob]

Re: My 3.0 mercruiser sucks

Since you changed the plugs and cap, double check that the wires are plugged in the right place, you might have lots of spark but not at the right cyclinder at the right time.

 

[panterafuy]

Re: My 3.0 mercruiser sucks

alright, changed out points, dwell is good, no dice. with all the plugs out cranking, there is fuel coming out from all cyl. with the exception of the no. 2 cyl witch seems to be getting almost twice as much, but they all seem to be getting enough to at least run. not sure if i have a fuel filter at the pump, its a mecho jobber on the side of the block, but ill check, also, ill check the sock in the tank. aside from that the carb was in pretty good shape, everyting moves nicely and there was very little varnish, even in the jets and stuff. that doesnt sound like a junk carb to me, but ive been wrong before. also i know the plugs are right, made sure when i had the head and stuff off. those are also brand new and gapped to the spec on the sticker on the valve cover. also i know the firing order is right on the dist. i dont know where to go with this anymore, ive already picked all the good stuff out of my brain.

 

[Coors]

Re: My 3.0 mercruiser sucks

there is fuel coming out from all cyl. with the exception of the no. 2 cyl witch seems to be getting almost twice as much,

Too rich, flooding?

 

[CPro]

Re: My 3.0 mercruiser sucks

I just adjusted the timing on my Mercruiser and that has basically eliminated the backfiring & sputtering. The boat still doesn't accelerate all the way to the top end, but it has smoothed out quite a bit.

Maybe this would work for you as well?

 

[bruceb58]

Re: My 3.0 mercruiser sucks

aside from that the carb was in pretty good shape, everyting moves nicely and there was very little varnish, even in the jets and stuff. that doesnt sound like a junk carb to me, but ive been wrong before.

Unless you have x-ray vision, you can't tell if the carb needs rebuiding from the outside.

You say your dwell is good...what did you measure?

In your first post you mentioned chocolate shake...possible that you have a bad/riser/manifold and or a cracked block or head due to improper winterization. You mentioned condensation in a later post but I have seen condensation in an engine before and it usually doesn't make the oil look too bad..just a little frothiness on the oil cap.

 

[Don S]

Re: My 3.0 mercruiser sucks

When you have the engine running, check the clear hose from the fuel pump to the carb, is there fuel going into the carb???? That hose should not have fuel in it. If it does, that indicates the fuel pump is bad and the rough running is the warning that something is wrong.
If you run it too long like that, it will wash the oil out of the cylinders and destroy the rings.

Another test you could perform is a vacuum test to manifold vacuum. It may tell you what the problem is.
I'm with bruce, milky oil is NOT condensation.

 

[panterafuy]

Re: My 3.0 mercruiser sucks

i set the dewll with a feeler gauge and checked it with a dwell meter. i took the carb apart and cleaned everything, and every hole. all the butterflys move as they should and fuel is consistant with throtle. the float still floats and moves freely and the needle moves nicely. plus, i had the head off and cleaned and inspected everything, i didnt see anyting odd, no cracks, no evedense of leaks or even a bad head or intake gasket. how do i do a vacuum test and what am i looking for from it, and what is a riser and how could that put water in my oil?

 

[bruceb58]

Re: My 3.0 mercruiser sucks

part number 14 is a riser. If the joint between it and the manifold leaks, water can drain into the exhaust after you turn the motor off. That water can leak past an open valve and into the cylinders and past the rings.

How many degrees was the dwell?

 

[Don S]

Re: My 3.0 mercruiser sucks

there is fuel coming out from all cyl. with the exception of the no. 2 cyl witch seems to be getting almost twice as much,

You never answered may previous question about fuel in the clear hose either.

Also regarding your milky oil, how much over the full mark is the level?