Mercruiser 888 stalls immediately in drive / reverse

[lornemilz]

So I took my project boat out for a test today and ran into some frustrating issues.

History is
- New Plugs
- New Wires
- New Dist Cap and Rotor
- New oil filter
- New fuel filter
- Carb cleaned and assembled with new gaskets
- Fresh Gas
- New Ignition Coil
- Timing Set 8 * btdc

Preliminary testing was good. Boat fires right up, revs to about 4200 rpm. Engages forward, Engages reverse. Does not stall or spit and sputter.

So on the lake... I get it off the trailer, fire it up , put it in reverse and it stalls.
Crank it back up, put in reverse, stalls.

SO i make it over the dock, get a good push off and put it in drive, it stalls.
SO when it first goes into gear the carb back pops.
I adjust timing on the lake. No better.
I am able to get it into drive and idle out of the cove I docked in. Any throttle response is instant death.

I checked the ESA (neutral switch) , disabled it, put it in drive, still stalls.

I am down to possible fuel pump or carb setting.

Is there a way for me to test the motor under load without being in the water?

Can I replace the mechanical pump with an electric pump?

What else could be in the circuit causing this issue?

I can place the motor in neutral and rev without issue.

 

[DaveG55]

Re: Mercruiser 888 stalls immediately in drive / reverse

Not being an expert; my first thought would be a coroded or somehow impeeded lower shift cable. As I understand it the lower shift cable activates the shift interupt switch (which is susposed to BRIEFLY kill the engine) only when there is resistance to the prop (like in the water) but does not activate the shift interupt switch when the boat is out of the water. When the lower shift cable becomes coroded or is damaged in some way it does not allow the shift interupt switch to act quickly enough and kills the engine.

 

[lornemilz]

Re: Mercruiser 888 stalls immediately in drive / reverse

Lets go back a little more. First day on the boat after acquiring the project it would engage forward and reverse, it would not stall out or backfire. It would also not really exceed 10mph or 2000rpm . With engine cover removed it would SLOWLY accelerate to about 2700 rpm. End of the day the transom cracked and the outdrive would not engage in gear anymore.

Fast forward to present.

The only things that were changed should have not much bearing on its runability on the lake. Timing was set to a suggested degree based on a local boat mechanic. Distributor cap and rotor are a match for the one that came off but new. Plugs are NGK instead of Champion. Wires are wires. Filters stayed the same brand and number. Carb settings were not changed.

The shift cable could be a culprit but by bypassing it it should go into gear and not stall however the ease of entering drive may be less than adequate.

The carb was assembled per the diagram.

 

[dukebrown]

Re: Mercruiser 888 stalls immediately in drive / reverse

Sounds to me like the accelerator pump is not pumping. What carb is on your motor? If it is a Holley like my 888 it is easy to assemble the accelerator pump wrong. Also easy to test.

 

[haulnazz15]

Re: Mercruiser 888 stalls immediately in drive / reverse

I believe the base timing on a 302 should be 10 btdc. Also verify that you have the plug writes in the correct order.revving up in neutral means nothing, as it will do that running on half the cylinders.

 

[lornemilz]

Re: Mercruiser 888 stalls immediately in drive / reverse

carb is a rochester 2bbl . Timing was set at 8 degrees , at 10 degrees it ran a little lower rpm and stumbled a little easier. The firing order is an odd one. 15423678. We used a factory ford service manual to set plugs and timing. I suspect the carb as much as the next guy at this point.

 

[haulnazz15]

Re: Mercruiser 888 stalls immediately in drive / reverse

I would verify timing first, it should be @ 10BTDC. Here is a thread to reference the 888 timing and firing order. If it isn't running right at that timing with the firing order in the Merc manual (and supposedly in the thread below) then move onto something else. Don't compound problems with random timing settings. There were two firing orders for the 302's, make sure yours is the correct one for the cam you have.

http://forums.iboats.com/showthread.php?t=316019

 

[lornemilz]

Re: Mercruiser 888 stalls immediately in drive / reverse

Here is the update.

Motor is still not running.

Verified the firing order by pulling rocker covers, 13726548.
Verified spark to all cylinders
Verified Timing in the area of 5-10 btdc
Carb is pumping fuel into chamber.

Yesterday the firing order was different. 15426378 is how we ran it yesterday. Yesterday it cranked up and idled without issue. Today it will not fire.

The plugs tell a different story. Only 4 plugs are firing, the other 4 are not.

Compression test yielded another interesting dilemma. Cylinders 1,2,3,4,5,7,8 all within 90-105psi. Cylinder 6 shows 0 psi with the gauge on it. The valves open and close on cylinder 6. The piston moves up and down. Without a plug in it, engine rotating, it does suck and blow air. Either way it should still attempt to fire.

Coil and all electrical to it is correct.

The other suspect is the electronic ignition module. I did get a distributor and tune up kit. Originally I did not install the entire kit, only cap and rotor. Today we swapped out the rest however I do not have a dwell meter to set it.

We are seriously stumped over here and it seems most information is just incomplete. I am leaning towards finding more information on the Ford 302 than the basic mercruiser information I can find.

I replaced the starter today, it was rusty and putting an extreme load on the electrical.

 

[lornemilz]

Re: Mercruiser 888 stalls immediately in drive / reverse

Still having issues on idle, cant give the motor any gas without backfire and stall. I have exhausted my resources and connections on this motor to get it to run. Here is where we are at with the firing order, distributor location, and general area for timing.

The motor does crank right up, it stumbles and tries to idle around 1000rpm per my tach on the dash. Points gap is set at .020. Plug gap is .35. I pull the plugs and they are black every time I run it a few times.
After consulting a few other mechanics in my area the motor is no doubt a 351.

 

[Bondo]

Re: Mercruiser 888 stalls immediately in drive / reverse

Compression test yielded another interesting dilemma. Cylinders 1,2,3,4,5,7,8 all within 90-105psi. Cylinder 6 shows 0 psi with the gauge on it.

Ayuh,.... No wonder it don't wanta Run,... You have a Rebuildable Core motor,...

Not a Runnin' motor....

 

[lornemilz]

Re: Mercruiser 888 stalls immediately in drive / reverse

So today I attempted a leak down test on Cylinder 6. I pumped some air into that sucker and didnt hear it come out the valves or the intake. I did yet another compression test on the motor a few hours later for giggles and cylinder 6 is now at 110.

Keep in mind that I have been able to crank the motor and it will idle for 30 seconds or so at a time while we try to get it timed in. I did also check another cylinder and it was sitting just over 110. I am going to soak the plug holes with marvels over night and do another test in the morning before pulling the water pump to get in to that timing chain.

 

[mrdjflores]

Re: Mercruiser 888 stalls immediately in drive / reverse

from your picture, you have a 351w ford motor....should have the windsor firing order of 1-3-7-2-6-5-4-8....
2 things come to mind, if this motor has ever been out to have work done it?
1) changed cam and put in a 302 cam instead of a 351w cam
2) flywheel...friend of mine boat a boat couple years ago and was doing exactly what yours is doing...after trying to diagnose everything, we finally pulled the motor...right off the bat...motor had a flexplate on it instead of a flywheel...put the right flywheel on, problem solved.

boats use the manual flywheel, instead of an automatic flexplate, to get that spinning mass, so the drag from the prop in the water doesn't stall the engine...
i have bought several old ford marine engines just to get the heads and the flywheels....all ford marine engines from the early to late 70's had closed chamber, large valeve 351w heads (perfect for hot rods)...also, the manual flywheels are high;y soft after for people restoring old fords...boats use the manual flywheel and have never been turned or faced to have a clutch mounted to them.

my current boat has a mid 70's 888 in it....bought a new manual flywheel for it for about $100.....sold my original '70 manual flywheel for $275