1997 5.7L thunderbolt ignition. Slow crank

[findinghomer]

Hi guys Okay I've done a lot of research on the internet and iboat, and I'm stumped still. Hoping someone could steer me in the right direction with my individual problem. Took the boat out of storage from winter, everything fired up just fine, Strong crank and fired with minimal effort. went on the lake everything was fine except for a few hard starts went hot. I got it home to try to diagnose that problem and ran it on muffs , it fired right up nice and strong. I let it get to temperature so I can try a warm start by shutting it off and then restarting it 10 or 15 minutes later. I did that, and now I have a really slow crank as if I have a low battery. I know the batteries are 100% charged I even pulled the working battery out of my truck for testing, same issue. Figured I had a starter issue, because I replace it with an aftermarket one 7 years ago. So I just went ahead and got another one. Even with the brand new starter, it's still cranking slow. So I pulled all the plugs, no water came out, cranked it with the plugs out still cranks slow. My next step was to check all of my connections, I did notice one of my battery terminals was loose out of the eyelet. Figured that was my problem, so I redid it. Now it's nice and tight and even greased up. Still a slow crank. So I figured I should just redo all of my battery connections including to the starter, or maybe it's my ground? So I traced my ground wire on my battery, apparently the ground wire attaches to battery one, and just loops behind the engine attaches to the ground of the other battery, it's not grounded to the engine? Is that normal? I know that cable did short out about 10 years ago and melted the insulation to it, but being that it was just a ground cable I never fixed it. I'm thinking this could have something to do with it as well, but shouldn't it be attached to the engine? This is where I'm really confused now , the negative posts on each battery just attach to each other. I found the ground strap, there are two grounds coming off of them they are smaller wires, can't see where they go maybe a ground bus? the ground seems nice and tight but I just don't understand why the batteries aren't grounded lol. Anyway I'm pretty stuck and I got a boating trip in a couple weeks and I'd like to try to get it fixed so I figured I would reach out hoping someone can help me. Thanks!

 

[findinghomer]

Oh also the ground wire that loops behind the engine, it appears they are joined with some sort of battery terminal in the Middle with a bolt through it or something I can't really tell because the insulation melted to it. I think it's two eyelets ends of each cable being adjoined with a through bolt and nut. Or is that something else?

Also another thing of note, I also tried bypassing the ignition switch, by bridging the slave solenoid and also right at the starter. Still cranks slow

 

[alldodge]

traced my ground wire on my battery, apparently the ground wire attaches to battery one, and just loops behind the engine attaches to the ground of the other battery, it's not grounded to the engine? Is that normal?

No this isn't normal, Bat ground should go to one of the bolts on the flywheel housing.

 

[findinghomer]

No this isn't normal, Bat ground should go to one of the bolts on the flywheel housing.

This is my 16th year with the boat And I've never messed with the wiring , So it's been like this ever since I've owned the boat, I just figured I should redo all my battery cables to try to eliminate that as the problem. And that's when I found they just connect to each other. Also when I crank the engine the yellow wire with a red stripe drops to 9.22 volts at the starter. Forgot to mention that

 

[alldodge]

Connect a ground cable to block and see if your issue clears up

 

[nola mike]

So the batteries need to be grounded to SOMETHING or else nothing would work. If not the main ground strap, do you have a small wire connecting the harness or something? Can't imagine that any situation without a proper ground from the starter would work well for long.

 

[findinghomer]

So the batteries need to be grounded to SOMETHING or else nothing would work. If not the main ground strap, do you have a small wire connecting the harness or something? Can't imagine that any situation without a proper ground from the starter would work well for long.

Yeah that's what I was thinking, but my ground wire attaches from my bank 1 battery goes around the engine goes to some kind of terminal coupler directly behind the engine (But just floating it's not attached to the engine, it was attached to the firewall behind it) , then that wire goes to a wire loom along the stringers towards the other battery. I can't see exactly what's going on in the wire loom yet , but when it comes out of the wire loom suddenly there's two ground wires a fat one (which appears to be the one looping to the other battery) and a smaller one and then it attaches to the battery. But I don't see that wire attaching to anywhere on the block unless it attaches in that wire loom somehow from the main harness. But even if so it would be a small wire . I guess I'll just have to cut into that wire loom and see what's going on in there. But like I said it's been like this for 16 years never had an issue.

I was thinking of hooking my starting battery directly to the starter and bypassing my multi battery switch, And then run a fresh new ground isolating everything to that battery and that battery only and see if it starts cranking properly. I guess if I do that and it's still slow is the engine damaged? Or maybe the starters not adequate?

 

[findinghomer]

Connect a ground cable to block and see if your issue clears up

Yeah I think my next step is to remove the house battery completely out of the equation , then hook my f starting battery directly to the starter with a fresh positive cable and a fresh ground that's actually grounded to the engine. And see if my cranking returns to normal. If it doesn't that would eliminate my battery setup , my battery switch , the ground, my terminal connections, The batteries itself, and possibly the starter since it's a brand new one. Could it have anything to do with the coil? The thunderbolt ignition system? Engine problem?

 

[nola mike]

Pics maybe? Ohm out the block-->battery neg to see if you're missing something. Bad ground could definitely get worse if it's hot. Either way, easiest/best thing to do is run a proper ground like AD said.

 

[findinghomer]

So the batteries need to be grounded to SOMETHING or else nothing would work. If not the main ground strap, do you have a small wire connecting the harness or something? Can't imagine that any situation without a proper ground from the starter would work well for long.

But yeah the starter grounds through the mounting bolts to the block right? So the batteries have to be grounded in some way, I wonder if it's one of those smaller wires on the grounding strap comes off of that into that wire loom along the stringers and then onto the battery

Because now that I think about it that extra ground wire I mentioned earlier that comes out of that wire loom and attaches to the second battery is about the size that comes off of that ground strap. But I can't tell where it goes , it's too tight back there. I'm guessing that's the ground wire from the block. It's a small wire probably 10 gauge

 

[nola mike]

Could it have anything to do with the coil? The thunderbolt ignition system? Engine problem?

Not the ignition system. Engine less likely if only hot and you've ruled out a hydrolock.

 

[findinghomer]

So the batteries need to be grounded to SOMETHING or else nothing would work. If not the main ground strap, do you have a small wire connecting the harness or something? Can't imagine that any situation without a proper ground from the starter would work well for long.

Okay now I feel dumb. I cut open the wire loom that runs along the stringers. The battery is grounded to the flywheel housing. Then another cable attaches to the battery which connects to the other batteru. That battery cable is the one that was melted and really bad shape. So I think what I'm going to do is bypass my dual battery switch , and hook my starting battery directly to the starter and ground that with the brand new cable and see what it does with just the one battery. If that fixes it, I'll just buy all new cables for all of it, And rewire everything, But if it's still cranking slow , regardless of what battery I put in there,, what else could I check?

I appreciate you guys taking the time to help me troubleshoot this thank you

 

[findinghomer]

Okay guys, I have some 4 gauge power wire from an old amp kit, can I use that to make cables for this just to test it to see if it helps. It is 4 gauge but it's that really fine copper not the hard stiff ones. Currently my battery setup is with 6 gauge wire I just don't want to put a ton of money into new cables if that's not even going to fix it. Because I plan on getting fatter wires for the battery, But the current wires have worked for 15 years so before I go and spend all the money on that I just wanted to see if you guys think it's worth trying it with this wire I have

 

[alldodge]

Saying this just for clarification in case your swapping gauge numbers

A 4 gauge wire is larger than a 6 gauge, the smaller the number the larger the wire.

Currently my battery setup is with 6 gauge wire

6 AWG wire would be small for a 305 and can current will increase for a 350

Depending on how far away the Bat is from the starter which includes the Bat switch, I would expect 2 AWG. If your wires are actually 6 then using 4 would be better