Help! 1999 1900sr Engine and Electrical Problems

[precool26]

Hey guys! After scouring you guys website for a few days, I feel hopeful that you can help me, as you already have by past threads. Last year I bought a '99 1900SR. Its fitted with the 5.0 V8 Mercruiser with Thunderbolt V ignition.

Never have I actually jumped in this thing once, cranked it up, and thought to myself "Heck yea, I love my boat"... its been a pain since the first day.

Last season, my engine started to miss/backfire (Not sure how to tell the two apart yet) while cruising. It got so bad to where it was inoperable. I have since changed the dist cap and plugs, with a little improvement, but not for very long. Back to the misfiring. Have pulled my plug wires testing for spark and I get it on some wires, not on others.. It used to idle just fine, but when under a load, misfiring. Ive since had it in two seperate shops, both claiming they fixed it with a total carb clean, and timing realignment. Once out on the water again, idles fine, cruised fine for a few minutes, but anywhere in between wot and idle its missing like crazy.

Decided to throw my wakeboard on and test it. Pulled me up for about 1 minute and crapped out and died. Nothing since, not even a start.

Im sure I have missed a whole lot in this post, but is there anyone who can help me with this.

I am prepared to start troubleshooting my Thunderbolt V ignition system by way of threads Ive read on here, but when I got home today to start, I am not even getting power via my ignition switch. No alarm, no crank, no nothing. very frustrasting.

Please help!!! Maybe with you guys help, I can have a running boat again! Thanking you all in advance.

[mmwjr]

Regarding the missing/backfiring: Remove fuel filter/water separator and pour it into a glass jar, let settle and look for water or particles. It sounds like bad gas, how old is it? Was the boat sitting before you got it as they may have stirred up crud in the tank?

Regarding not cranking; verify the kill switch on the helm control is in the run position. Also verify the engine breaker is set; red button. it's mounted on the engine near the harness plug. Harness plug can also come loose.

Post back after checking these.

[precool26]

I sure will! On my way to work now but when I get off ill mess with it again
I know that the kill switch was not engaged, but I do not have a lanyard. I just have it flipped to the ON position. As far as the gas situation, I just replaced the water fuel seperator, and put fresh gas in it. I'll pull it today though! I'll send pics too
thank you

[mmwjr]

Also the shift cable must be in neutral in order for the engine to crank. i.e. shifter in neutral or push button to disengage shift when advancing the throttle.

You probably know this but I have had folks who do not.

[shrew]

Originally Posted by mmwjr

Also the shift cable must be in neutral in order for the engine to crank. i.e. shifter in neutral or push button to disengage shift when advancing the throttle.

You probably know this but I have had folks who do not.

I've seen situations where you have to turn the shutoff off and then on again, like it was in on position, but not making contact.

I've seen the same with the shifter looking like it was in neutral, but still actuating the starter 'interupt'. Shifting it into gear, then back into neutral can fix that issue too.

[precool26]

I'm getting nothing at my key... Reading 13v at the wire on back of ignition, but nothing when I turn key, or even jump hot to ignition. Not turning over, nothing....

[mmwjr]

So power on the B terminal of the ignition switch, correct?

When holding the key in the start position do you get power on the S terminal?

When the key is in the run position do you get power on the I terminal?

B for battery, S for start, and I for ignition.

If these are ok then you need to see if the slave soleniod is getting power on the low current terminals. If not the neutral safety switch is open or faulty.

If you are getting power to the slave soleniod and it is not closing, clicking it's either bad or you battery is not providing power under load. Measure the battery to see if the voltage drops when someone try's cranking the engine.

[precool26]

Thank you shrew and mmwjr. After a little messing around and checking terminals in my dash, the problem has corrected itself, or I fixed it when I rewired my radio the correct way, rather then splicing into the first hot I found (omw to lake last season in a hurry, amateur boat owner). Also, as far as the engine I concerned, I started checking plug wires and plugs and found one loose at the plug on my engine. She is purring and driving somewhat nice. After taking her out for a spin she performed well, with one minor miss/ backfire at first, with none to follow. I only ran her for about 20 mins though... Would that be normal?

Also, I notice someone has piggybacked the two wires that are on the starboard side of my engine located at my oil pressure sensor maybe. I plugged the wires back into the sensor, but got no gas from fuel pump when turning boat on. Replaced the piggyback and she gassed right up? Any comments??

Thank you guys!

[mmwjr]

If the initial backfire was when the engine was cold the choke may be a little sticky.

You have an electric fuel pump, that is a safety switch that opens if the oil pressure is low. It's bad and should be replaced. With the jumper in place the fuel pump will continue to run if the engine stalls and may result in fuel overflowing the carb and a fire may result.

BTY call me Mike

[precool26]

Thanks Mike. Ill have to get me a new one soon.

What is the difference between a miss and a backfire? Would I be able to tell the difference in the two sounds?

[precool26]

btw... what part is that exactly with the prongs for the two wires on the oil pressure sender. Seems the switch is that round piece with the one wire on the tip of it. What is the part that the two wires actually hook to called?

[mmwjr]

A miss is when a cylinder does not fire and a backfire is due to a timing issue that results in fuel igniting when the intake valve is open and resultant gases blow back up through the carb. A backfire can also be due to an improperly operating carb that dumps to much fuel.

[mmwjr]

The smaller one with two wires is the oil pressure switch that provides power to the fuel pump, the other is the oil pressure sendor that is connected to the oil pressure gauge at the helm. It's resistance changes with OP (oil pressure) which varies the current through the gauge and the needle deflection is the result.

[precool26]

Help again! On the water now... Everything ran great for about mins. Then yhe backfires started anywhere in between idle and 3/4 full thottle... Now i cant even get to full throttle, backfiring like crazy... Help Mike!!!

[mmwjr]

Originally Posted by precool26

Help again! On the water now... Everything ran great for about mins. Then yhe backfires started anywhere in between idle and 3/4 full thottle... Now i cant even get to full throttle, backfiring like crazy... Help Mike!!!

Have you checked the ignition timing? Thunderbolt V requires a wire to be grounded to set base timing. Google for how to set mercruiser Thunderbolt V timing.

When on the water use the timing light to verify the timing is advancing correctly.

Fuel can be an issue, temporary use a portable gas can in place of the built in fuel tank to see if that makes a difference.

[precool26]

Havent messed with the timing. Dont have a light handy... Would it be a timing issue co sidering my idle and wot are fine? Could my icm be going out?

[mmwjr]

Originally Posted by precool26

Havent messed with the timing. Dont have a light handy... Would it be a timing issue co sidering my idle and wot are fine? Could my icm be going out?

If you can hit WOT the timing is probably ok. For electrical I would suspect either the coil or ignition sensor in the distributor before the icm.

[precool26]

If im not mistaken, i can test both those parts seperately reading some guides on here... Correct?

I just know that nobody around here knowz how to fix it apparently, its feels like a hopeless situation...

[precool26]

Maybe i should add the fact that my tach has never worked since i bought the thing. Im assuming im reaching wot based on the sound of my rpms as compared to before... Im just stumped

[mmwjr]

So where in the world are you?

Got a Harbor Freight near you? Go buy a cheap timing light and tach/ dewell meter.

The tach gets its signal fron the negative terminal on the coil, gray wire. Check the connections at both ends.

Do you have a Merc manual and wiring diagrams? If not get them from the Documents tab of this site.