T Bolt IV to MSD Ignition

[mikeav85]

hi all, new to the forum and first time boat owner. picked up a 1990 Arriva 2450 CBB 454 7.4 bravo1 earlier this year. engine has just been rebuilt. spent last week putting in new manifolds, risers, a starter, fuel pump, fuel line, spark plugs and wires, and a thermostat. when i finished everything i checked and double checked my firing order before i started it. the first time it started fine, it ran for about 3 mins then i turned it off to restarted it and recheck things. when i went to start it again i turned the key to the ON position and heard clicking/spark sound coming from the top of the block and my tach was jumping around, then when i pushed the key to start the engine it turned over and came on as normal. while my engine was at idle my tach jumps around from 2000 to 2500 but when i give it gas the needle drops down and reads properly and continues to do so when ever i'm given the engine gas. i turned of the engine tried it again. this time no more click/spark sound but my tach starts jumping as soon as i turn the key to the ON position and when ever the engine is at idle. the engine does NOT jump around at idle, it runs smooth, just my tach needle. any help please. boat is a 1990, how can i tell if i have an 89 or 90 engine. i read that the 89 was rated at 330hp and the 90 at 300 but from what i can see both engine have all the same specs and requirements/parts????

 

[tinkerguy70]

Re: TACH jumping around ONLY at idle

Re: TACH jumping around ONLY at idle

First of all, better punctuation and sentence/paragraph structure would make it a lot easier to read your posts and give you a good answer.
Secondly, it sounds like you have a bad or loose connection somewhere in the wiring for the tach. Every tach I've ever seen that jumped around like that had a loose or bad connection somewhere. Usually, you'll find it at the coil.
Start looking at the wires and connectors that go to the tach and I think you'll find a corroded or loose connection somewhere.

 

[Don S]

Re: TACH jumping around ONLY at idle

Re: TACH jumping around ONLY at idle

Check the coil tower, and wires. Sounds like you have spark arching to the - terminal of the coil which will make the tach jump around.
Faulty cap, faulty plug wire, or a faulty spark plug will cause the coil tower to arch to the other coil terminals. This can also crack the coil tower itself.

The engines MerCruiser serial number is needed for proper ID of year and HP rating.

 

[tazrig]

Re: TACH jumping around ONLY at idle

Re: TACH jumping around ONLY at idle

hi all, new to the forum and first time boat owner. picked up a 1990 Arriva 2450 CBB 454 7.4 bravo1 earlier this year. engine has just been rebuilt. spent last week putting in new manifolds, risers, a starter, fuel pump, fuel line, spark plugs and wires, and a thermostat. when i finished everything i checked and double checked my firing order before i started it. the first time it started fine, it ran for about 3 mins then i turned it off to restarted it and recheck things. when i went to start it again i turned the key to the ON position and heard clicking/spark sound coming from the top of the block and my tach was jumping around, then when i pushed the key to start the engine it turned over and came on as normal. while my engine was at idle my tach jumps around from 2000 to 2500 but when i give it gas the needle drops down and reads properly and continues to do so when ever i'm given the engine gas. i turned of the engine tried it again. this time no more click/spark sound but my tach starts jumping as soon as i turn the key to the ON position and when ever the engine is at idle. the engine does NOT jump around at idle, it runs smooth, just my tach needle. any help please. boat is a 1990, how can i tell if i have an 89 or 90 engine. i read that the 89 was rated at 330hp and the 90 at 300 but from what i can see both engine have all the same specs and requirements/parts????

The sparking sounds like a bad connection at the coil. Also check for a bad ground wire. (usually green wire coming off of the negative terminal on the coil going to you your tach)

 

[mikeav85]

Re: TACH jumping around ONLY at idle

Re: TACH jumping around ONLY at idle

thank you all for the advice, i will take a look at all of the connections behind the gauge and on the coil this weekend and report back what i find.

 

[grewvin1]

Re: TACH jumping around ONLY at idle

Re: TACH jumping around ONLY at idle

Once one of mine did the same, from an older post they suggested: on back of tack, switch to change from 8cyl, to 6cyl or 4. give switch a couple of turns from one end to the other. Possible the contacts have corrosion, I took my screwdriver and switched it back and forth a few times now steady as a rock.

 

[mikeav85]

Re: TACH jumping around ONLY at idle

Re: TACH jumping around ONLY at idle

Once one of mine did the same, from an older post they suggested: on back of tack, switch to change from 8cyl, to 6cyl or 4. give switch a couple of turns from one end to the other. Possible the contacts have corrosion, I took my screwdriver and switched it back and forth a few times now steady as a rock.

thanks. i got a new set of plug wires and a cap and rotor kit, seeing as how everything else on the engine is new I thought I should go ahead and do it. I will check all the connections and try your trick with the gauge before i put any of the new hardware on to see of any of it clears up the problem.

 

[mikeav85]

Re: TACH jumping around ONLY at idle

Re: TACH jumping around ONLY at idle

I got a chance to look at all of the connection on the coil and everything was tight and clean. I put in the new cap and rotor along with the new set of plug wires. after i put everything in i got a littler curious so i turned on my batteries and turned the key to the ON position and my tach needle instantly jumped down to zero instead of jumping around the 2000 rpm range. i hope putting in the new hardware solves the problem and it was just a problem with a bad connection or a faulty wire/connection. i won't know until i get a chance to start the engine this coming weekend, here's keeping my fingers crossed. thanks for all the great advice and help from everyone.

 

[tazrig]

Re: TACH jumping around ONLY at idle

Re: TACH jumping around ONLY at idle

Hopefully you killed the electrical gremlin. If not I'd recheck the coil like Don suggested. Sometimes the coil can look fine on the outside but be toast on the inside.

 

[mikeav85]

Re: TACH jumping around ONLY at idle

Re: TACH jumping around ONLY at idle

hi everyone, so i finally got a chance to start the boat and no good. I get spark as soon as i turn the key then i get no spark and then as soon as i let go of the key there is spark and the engine back fires and white smoke comes out of the flame arrestor. the local shop said that my Tbolt-iv system is no good. they gave me two options; either put in an MSD distributor and coil and get rid of the stock distributor, coil and control box on the port riser. Option two is to put in a MSD distributor, coil, and 6AL box. Is anyone familiar with any of this equipment? should i jump in and make the switch or should I go through the entire system and look for bad grounds or connections. I guess my concern is that it's a 23 year old system and is it just time to revamp and put in the MSD with the rev limiter and multi spark system?

 

[mikeav85]

Re: TACH jumping around ONLY at idle

Re: TACH jumping around ONLY at idle

hi everyone, so i finally got a chance to start the boat and no good. I get spark as soon as i turn the key then i get no spark and then as soon as i let go of the key there is spark and the engine back fires and white smoke comes out of the flame arrestor. the local shop said that my Tbolt-iv system is no good. they gave me two options; either put in an MSD distributor and coil and get rid of the stock distributor, coil and control box on the port riser. Option two is to put in a MSD distributor, coil, and 6AL box. Is anyone familiar with any of this equipment? should i jump in and make the switch or should I go through the entire system and look for bad grounds or connections. I guess my concern is that it's a 23 year old system and is it just time to revamp and put in the MSD with the rev limiter and multi spark system?

i forgot to mention that i'm looking at the 8560 distributor, noise reducer, high vibration coil, and can't decide between the 6al or 6m-2l boxes. one is marine certified and i don't think that the 6al is marine certified but i see it used a lot in marine applications, can anyone help?

 

[mikeav85]

T Bolt IV to MSD Ignition

hi everyone, so i finally got a chance to start the boat and no good. I get spark as soon as i turn the key then i get no spark and then as soon as i let go of the key there is spark and the engine back fires and white smoke comes out of the flame arrestor. the local shop said that my Tbolt-iv system is no good. they gave me two options; either put in an MSD distributor and coil and get rid of the stock distributor, coil and control box on the port riser. Option two is to put in a MSD distributor, coil, and 6AL box. Is anyone familiar with any of this equipment? should i jump in and make the switch or should I go through the entire system and look for bad grounds or connections. I guess my concern is that it's a 23 year old system and is it just time to revamp and put in the MSD with the rev limiter and multi spark system?

i forgot to mention that i'm looking at the 8560 distributor, noise reducer, high vibration coil, and can't decide between the 6al or 6m-2l boxes. one is marine certified and i don't think that the 6al is marine certified but i see it used a lot in marine applications, can anyone help?

 

[achris]

Re: T Bolt IV to MSD Ignition

For those who haven't been following all the threads... This is the link to the thread that this should have been the next post to...

http://forums.iboats.com/mercruiser...ping-around-only-idle-587893.html#post4066291

 

[Bondo]

Re: T Bolt IV to MSD Ignition

hi everyone, so i finally got a chance to start the boat and no good. I get spark as soon as i turn the key then i get no spark and then as soon as i let go of the key there is spark and the engine back fires and white smoke comes out of the flame arrestor. the local shop said that my Tbolt-iv system is no good. they gave me two options; either put in an MSD distributor and coil and get rid of the stock distributor, coil and control box on the port riser. Option two is to put in a MSD distributor, coil, and 6AL box. Is anyone familiar with any of this equipment? should i jump in and make the switch or should I go through the entire system and look for bad grounds or connections. I guess my concern is that it's a 23 year old system and is it just time to revamp and put in the MSD with the rev limiter and multi spark system?

i forgot to mention that i'm looking at the 8560 distributor, noise reducer, high vibration coil, and can't decide between the 6al or 6m-2l boxes. one is marine certified and i don't think that the 6al is marine certified but i see it used a lot in marine applications, can anyone help?

Ayuh,.... Why the second thread, 'bout the Same topic,..??

You need a different Shop,.... The T-bolt system is 1 of the Best to ever hit the water....

'n Both of the options that shop offered, Ain't nearly the best....

I'd either sort out the T-Bolt IV, or scrap it for the Delco EST system...

 

[ENSIGN]

Re: T Bolt IV to MSD Ignition

I agree with Bondo,Keep the T-bolt ignition.

 

[mikeav85]

Re: T Bolt IV to MSD Ignition

k i'm going to start taking a look at everything tomorrow. If i end up in a dead end i will start looking at the Delco EST kit. I noticed that kit does not have a control box, does it use the stock box or does it eliminate it from the system?

 

[Bondo]

Re: T Bolt IV to MSD Ignition

k i'm going to start taking a look at everything tomorrow. If i end up in a dead end i will start looking at the Delco EST kit. I noticed that kit does not have a control box, does it use the stock box or does it eliminate it from the system?

Ayuh,.... It's a self-contained unit....

 

[mikeav85]

Re: T Bolt IV to MSD Ignition

No good. Checked all the wires in the ignition system and everything looks good, tight, and clean and still no start. I guess that just leaves me with a problem with the ecm which I don't plan on replacing. I think it might be time to start looking at the Delco EST. thanks for all the help.

 

[achris]

Re: T Bolt IV to MSD Ignition

Have you run through the TB-IV troubleshooting chart?

 

[mikeav85]

Re: T Bolt IV to MSD Ignition

I have not but I took it to the mercruiser shop where they put it on the dyno and ran diagnostics and came up with a bad ECM and a bad pick up in the distributor. It more cost effective to put in a fresh system. They want me to fix the T-bolt but it just seems like a waste of money for me to pump so much into a 23 year old system, what you think.