1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

[Don S]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

All electrical items such as distributors, starters, alternators, relays, etc. can spark. Marine parts are shielded to prevent sparks from igniting fumes in the bilge.
Fuel systems are also marine rated. I would bet from seeing parts of your engine in the videos, that your shop just stuck in a truck engine.
Probably the truck carb and fuel pump too. Those are two items that really need to be marine parts for safety. The marine parts are designed to not leak fuel into the bilge or onto the engine. If the carb float sticks, the fuel is directed into the engine, if you have a mechanical fuel pump, if the diaphragm fails on the automotive engine, the gas just goes into the bilge. With a marine pump, the fuel is again directed to the carb and into the engine. An engine running really rich usually means you have a problem you should be looking into.

 

[81 Checkmate]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Just seen your last post. You can do this yourself with the help on here. Its not that big of a deal.
We will have you up and running before winter sets in. HA! HA! Just kidden

Im sure Don will post you the right manuals for ya. if not goggle is your friend!

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

checkmate yes I have torn into an engine before ... it has been a while. I did not purchase the boat from the so called shop. Yeah the reason I wanted the clarification on the distributor is because it does work lol Im a big believer in if its not broke dont fix it. That being said I have small children and do not want to have any unnecessary risk while on the water. Any ideas where the best place to get an aftermarket ignition system (guessing i will have to replace almost everything so I know its right) for a decent price? I dont wanna risk a big KABOOM especially with my kids onboard.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

All electrical items such as distributors, starters, alternators, relays, etc. can spark. Marine parts are shielded to prevent sparks from igniting fumes in the bilge.
Fuel systems are also marine rated. I would bet from seeing parts of your engine in the videos, that your shop just stuck in a truck engine.
Probably the truck carb and fuel pump too. Those are two items that really need to be marine parts for safety. The marine parts are designed to not leak fuel into the bilge or onto the engine. If the carb float sticks, the fuel is directed into the engine, if you have a mechanical fuel pump, if the diaphragm fails on the automotive engine, the gas just goes into the bilge. With a marine pump, the fuel is again directed to the carb and into the engine. An engine running really rich usually means you have a problem you should be looking into.

Don,
To clarify I purchased the boat from a third party not the shop. Only reason i took it to the shop to winterize it was because I was busy at work and didnt have time to do it myself. they only fogged and put antifreeze in it (at least thats what they said) which is why i was going ahead and doing all other maintenance now. (want to make sure its safe reliable and ready to go) as for the carb and fuel pump. how do i tell if they are automotive or marine or should i just replace them? I can post pictures if need be tonight and also I will get you the s/n off the block this evening. the s/n off the plastic piece on top of the motor says 0F608760 but i will verify the block number tonight. Im also guessing there is a way to check the starter and alternator to see if they are marinized?

I dont mind spending some of my time and money as long as I know im doing it right and I will get the desired effect in the end. Thanks to everyone who is helping me out it is greatly appreciated.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Just seen your last post. You can do this yourself with the help on here. Its not that big of a deal.
We will have you up and running before winter sets in. HA! HA! Just kidden

winter lmao In all honesty Im shooting for 2-3 weeks ready to go but that may be just a dream depending on parts availability and price not to mention time ... gets difficult on a limited budget and little ones running around everywhere

 

[Don S]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Take the plastic cover and flame arrestor off the engine and take some clear photos of the carb and the fuel pump.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Take the plastic cover and flame arrestor off the engine and take some clear photos of the carb and the fuel pump.

Ok I will do that this evening and post pictures as soon as I do.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Ok guys got home this evening and started her up with the valve cover off and tightened the nut on top of the rocker arm only about 1/8 of a turn and BAM no more tap. started losening it up till it tapped again then tightened just enough to stop the tap ... attempted to take a video of me doing this but it didnt save for whatever reason

Don
Below are pictures of the carb hope this helps.

 

[Don S]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Well the one picture that was actually big enough to see, looks like the Mercruiser carb.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Sorry Don I tried to get them as large as possible not sure how to put them in the thread the best way. I Think im going to replace that lock nut on top of #2 exhaust rocker. Im guessing they sometimes ware out and come a little lose? Should I replace all of them or just the one? Actually sounds good now that the tap is gone ... idling much better after the new plugs too ... back to 650 rpm at idle instead of 800-850.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Don does this help any? I found your thread about posting them in the body followed it and first two are still rather small.

 

[Don S]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

The carb has been confirmed as marine, it's everything else on the engine we can't see that is suspect. Close ups of an individual item only allows us to see one item at a time. Let us see the rest of the engine with some size to see things.

 

[Pete104]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

The original ignition system is entirely gone! Judging by the mildew everywhere, it's been like this for awhile. Not only is the "GM HEI" not safe, the ain't got tires! Engine ain't getting the proper advance for the timing.
The noise? If you got an 1/8th of a turn & stopped the noise, pull the heads & take a real close look!

 

[81 Checkmate]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Don do you see a PCV Valve in the pic?

Coopin - Your rocker arm stud nut that you tighten up normally doesnt just loosen up. Something has caused this!

Did ya check across the top of the rocker studs with a straight edge? This would eliminate a stud that is pulling out!

I would bet you have a bad cam lobe or a calasped lifter or bad valve spring.

 

[Don S]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

I would bet you have a bad cam lobe or a calasped lifter or bad valve spring.

Would be very easy to check.With a remote starter button hooked up and the coil wire grounded, crank the engine over while holding down on the lifter on the push rod side and seeing how much up and down movement there is. Should be the same amount as the others. If not, the cam lobe is gone.

 

[RogersJetboat454]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Would be very easy to check.With a remote starter button hooked up and the coil wire grounded, crank the engine over while holding down on the lifter on the push rod side and seeing how much up and down movement there is. Should be the same amount as the others. If not, the cam lobe is gone.

+1 ^^^^

And a compression test wouldn't hurt either.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Ok guys sorry it took so long for me to reply this time busy with work but when I get home this evening I will try what you said Don. First I will put a staight edge across the top of the rocker bolts and make sure they are level and go from there. In all honesty I really think that the "lock nut" or what ever you call it that holds the rocker in place is bad (lock part not holding). Not sure if there is a way to test that or not. Im also going to count the threads on each bolt and compare them. There is a PCV valve on both valve covers. Next question I have is reguarding the "Bad Cam Lobe" idea. Wouldnt you have to run the thing for this to happen. I just dont see how a cam lobe can go bad from sitting (no tap before stored for winter .... tap on first startup of the season) Please tell me if im mistaken here. Either way I will try what don mentioned above and let you know my results.

Pete 104 Im a little confused as to why you say its been there so long because of mildew there is no mildew that I have seen paint pealing but no mildew unless your talking about something else.

Any sujestions on decent priced ingnition kits for my application?

Don I will get some more engine picts posted sometime this evening.

 

[RogersJetboat454]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

I just dont see how a cam lobe can go bad from sitting (no tap before stored for winter .... tap on first startup of the season) Any sujestions on decent priced ingnition kits for my application?

The same argument could be made for your lock nut theory. How does it go bad just by sitting over the winter? If you put a socket on the nut and back it off, and notice it has resistance, I would say your lock nut isn't the issue.

Perhaps that lobe on the cam had the valve open all winter, and its lifter bled down, and has not recovered.

As far as an ignition kit, this would be your best bang for your buck deal;
http://www.michiganmotorz.com/delco-voyager-marine-electronic-distributor-p-119.html

 

[tpenfield]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Is that a 2 barrel carb that we were seeing on this motor???

So, as long as we are ordering parts maybe a 4 bbl carb and a new intake manifold?

 

[Pete104]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

I'm just noticing the "yuck" on the wires, the cap & generally all around the underside of the flame arrestor cover!