NEED HELP ASAP!!!!! Mercruiser 4.3 thunderbolt IV

[a8218]

I just recently bought a new boat. Going on a little over a month now. its a 93 bayliner capri 2051 with a 4.3 v6 mercruiser. had it out on the water several times with no issues at all. Have a big day planned at the lake in the morning with the family and I'm in a bit of a bind. I just thought itd be a good idea to do a quick tune up on some simple, basic things.....changed the plugs and wires, and installed a 2nd battery with a marine battery selector switch. checked the oil and the outdrive gear oil. nothing else was touched. installed the new plugs and wires, all factory recommended marine parts. I have gotten the firing order wrong the first go around. I took it to the river to make sure everything was running well for the trip tomorrow and it just sputtered around, I tried to give it throttle and it just bogged down. stayed running but wouldn't go any faster than wake speed. I realized once i got home i had gotten the firing order wrong, so I reinstalled all the plugs wires in the correct firing order to the best of my ability, assuming the timing is in line with the numbers on the distributor cap. still runs very rough, backfires and dies, worse than it was before. I got it running and started to pull plug wires to check to see all cylinders were firing and as I pulled them nothing happened with the idle. Just the coil started arcing. I thought just maybe I had faulty parts. I reinstalled the old plugs and wires in what seemed to be the correct firing order just to get on the lake tomorrow but its still the same issue. running rough backfiring both through the exhaust and the carb. this boat ran wonderfully before this and I'm sure its my error and it maybe as simple as the firing order off from what the distributor is showing. but how do I check that? or what else could be causing these issues? any insight at all would be greatly appreciated.

 

[achris]

Turn the engine until the timing marks on the crankshaft pulley line up with the marks on the timing cover. This will be TDC on #1 and #4. Remove the spark plug from #1 cylinder. Get a length of hose and push it onto the cylinder head at the spark plug hole. You should be able to get a reasonable enough seal at the end of the hose. Blow into the hose. If the air escapes easily and you hear it coming out through the carb, the engine is at overlap #1. If the pressure builds up and only escapes around the end of the hose, that is firing #1.

If you are at TDC on 'valve overlap' of #1, then turn the engine one more full turn of the crankshaft. That will bring you to firing on #1. Remove the distributor cap and see which post the rotor is pointing at. Check your firing order accordingly.

Chris..........

 

[a8218]

Thank you very much for the fast reply. Seems I have my cylinder numbering correct, I will do test first thing in the morning and return with my results. Does this seem to be the only likely issue to you also?

 

[achris]

The only other possiblity is that with the plugs wired wrong it sucked water into a cylinder. In the process of the above test, pull all the plugs and spin the engine over on the starter and see if you get any water come out.

Chris....

 

[NHGuy]

it's possible to snap the ceramic tops of the spark plugs too. If you felt any pops while tightening your spark plugs there may be some that are broken internally. That interrupts the current to the plug tip and causes a misfire.

 

[achris]

it's possible to snap the ceramic tops of the spark plugs too. If you felt any pops while tightening your spark plugs there may be some that are broken internally. That interrupts the current to the plug tip and causes a misfire.

That too.

 

[chartersj]

Turn the engine until the timing marks on the crankshaft pulley line up with the marks on the timing cover. This will be TDC on #1 and #4. Remove the spark plug from #1 cylinder. Get a length of hose and push it onto the cylinder head at the spark plug hole. You should be able to get a reasonable enough seal at the end of the hose. Blow into the hose. If the air escapes easily and you hear it coming out through the carb, the engine is at overlap #1. If the pressure builds up and only escapes around the end of the hose, that is firing #1.

If you are at TDC on 'valve overlap' of #1, then turn the engine one more full turn of the crankshaft. That will bring you to firing on #1. Remove the distributor cap and see which post the rotor is pointing at. Check your firing order accordingly.

Chris..........

Not to hijack a thread,,,,but I am also trying to figure out the timing for my first time after swapping out a block...I have the motor at TDC, and looking at your picture, isn't #1 on the cap, and the rotor, suppose to point to #1 cylinder? I fit the distributor in with the rotor pointing to #1 cylinder, but when I put the cap on its on the #4 position on the cap...

 

[a8218]

So I have pulled the plug one cylinder one. Sitting inside the boat looking at the motor. The first cylinder on the right or port side of the motor is at TDC right now. The way the distributor cap is, the rotor button is hitting at the #4 cylinder right now. So do I turn the distributor cap to where now #1 is where #4 ? No spark plugs broke off and when I removed the spark plugs there were no signs of any moisture.

 

[a8218]

TDC on cylinder one. Should my rotor button be facing to the front of the boat. Toward the carb.

 

[Bt Doctur]

The rotor faces the #1 position in the cap. Dont know where you get the idea it faces a cylinder

For those who put their engines together:
rotate the motor untill #1 intake valve opens and closes. this it #1 coming up on compression
slowly rotate motor untill the timing mark is at "0" This is #1 TDC compression
Install dist with rotor facing #1 in the cap. If cap is not numbered designate a #1 position and point rotor to that part of the cap
If a GM v8 plug wires in the dist are clockwise 1,8,4,3,6,5,7,2

 

[Silvertip]

Stop over-thinking this. When you are told that the rotor should point to #1 cylinder, it means the rotor should point to the distributor cap terminal whose wire feeds #1 cylinder. If you have not rotated the engine, #1 position for the rotor will not have changed. If you have rotated the engine, you need to get it rotated back to TDC (on the compression stroke) to establish the #1 distributor position. Remember, the crankshaft rotates twice to make the distributor turn once. Therefore TDC can be 180 degrees off if you are not on the compression stroke. You obviously screwed up the firing order when you installed the new wires. Unless you understand the firing order concept, you are advised to replace one wire at a time rather than pulling all of them and then fumbling through the process. The value of a factory service manual cannot be over-stated, especially for the novice mechanic.

 

[achris]

So I have pulled the plug one cylinder one. Sitting inside the boat looking at the motor. The first cylinder on the right or port side of the motor is at TDC right now. The way the distributor cap is, the rotor button is hitting at the #4 cylinder right now. So do I turn the distributor cap to where now #1 is where #4 ? No spark plugs broke off and when I removed the spark plugs there were no signs of any moisture.

If you are sure the crankshaft is at #1 FIRING top, then you have done something wrong. If you only replaced the leads, and didn't move the distributor, I would suggest you have the engine at #1 overlap, not firing. Turn the crankshaft another full turn. The rotor will then be 'hitting' on #1.

Chris........

 

[2fishy4u]

"The value of a factory service manual cannot be over-stated, especially for the novice mechanic."

That right there will save you many hours of guessing.

 

[achris]

"The value of a factory service manual cannot be over-stated, especially for the novice mechanic."

That right there will save you many hours of guessing.

I'm not exactly a 'novice mechanic', but here is PART of my library (I have about 10 times that as PDFs)...

 

[nola mike]

That "Excel 2003" bible is no doubt what separates you from the novice mechanics

 

[Silvertip]

I'm not exactly a 'novice mechanic', but here is PART of my library (I have about 10 times that as PDFs)...

Having the manuals and following/understanding them are separate issues. I once knew a fellow with a EE who couldn't change a light switch and be reasonably certain the light would work when done and he admitted it.

 

[harleyman1975]

I like the Mercruiser for Dummies! LOL! Yeah yeah I know but it still was funny to me.

 

[a8218]

Thank you greatly for the help. I got the firing issue worked out. After pulling everything back off and rewiring as you stated she fired right up. Ran great. I immediately took it to the river this morning as it's a 7 min drive from my house. Fired right up, pulled it off the trailer and hit plane in less than 5 seconds. Took it for a 20min ride back and forth. Loaded it back up to pick up the wife and kids to make the hour drive to the lake for the day. Again backed the trailer in, again fired right up. Backed it off the trailer took a little spin waiting for the truck to be parked. Came back in to the dock went to hit reverse to slow and and it sprung forward. Didn't tear anything up but now I've lost reverse completely. The cable from the throttle handle acts as if it's shifting forward. And moves the shifting control arm and the momentary kill switch only in the forward position. When tried to put into reverse the kill switch lever doesn't move. Only the throttle cable. So it seems as if I'm stuck in forward. But when given throttle forward anything past the in gear detent it dies. Doesn't seem like I can catch a break. I thought I was a decent mechanic until I screwed up a simple plug wire change. That's a first lol but I'm defenitly looking into some manuals for sure. Any recommendations would be great. Thanks for all you all do here its a great help to us novice marine mechanics.

 

[Bondo]

That's a first lol but I'm defenitly looking into some manuals for sure. Any recommendations would be great.

Ayuh,..... Welcome Aboard,..... In my signature, click on "Don'S Adults Only Section",....

Scroll down to the Merc Info tab,....
In there scroll down to the Factory Manuals link, 'n click it,....
In the library, scroll down to Mercruiser, then side-scroll to yer motor, 'n drive,....

 

[a8218]

Excellent thank you. Does anyone have a suggestion on where to start with my most recent issue at hand? The cables from the throttle handle seem fine. I'm thinking it's the shift cable that goes from the adjustment rods beside the carb to whatever makes the outboard shift from forward to reverse. I'm going to get the manual that was suggested and look thru it before I really dig in. Just looking for some suggestions on what could have went wrong here.