Logo
FULL SITE MENU

84 Mercruiser InLine 4 140

C

Chip Timm

New member
I have the 84 Mercruiser In Line 4 Cylinder 140 HP motor. 3 years ago when I went to start it up after the winter, I couldn't get a spark from the ignition coil. I was told that replacing the points was usually the cause of that so I replaced them and it fired right up. The next 2 years, same thing. At 17.99 for the points and condensor, I figured no big deal, replaced them and it would start right up. This year, no such luck. I however only replaced the points. Now I don't believe that replacing the points was the only problem, but it was the easy fix. Now since those don't work, what other possibilities are there? Should I still replace the condensor? Is it likely that the dist. cap is letting moisture in and that's what's failing the points over the winter? Is it possible that the ignition coil itself is not working properly, and if so, how can I test that? Any help in this would be greatly appreciated.
 
Chances are it's the condenser. The condensers go bad when they have a full 12 volts to the points. The voltage to the ignition coil has to be resisted down to about 9 volts. You need a digital volt meter and need to check the voltage at the purple wire on the coil. It should be 9 volts or less.
 
Thanks, I'm going to try a new condensor then. Those are also only a couple of bucks. After I posted this last night though I got to searching around and saw the conversion kit. Is there any merit to going with this? It looked like it may save a lot of hassle in the future and may be more efficient.
 
no conversion kit. You have a kill switch ? Pull it and reset it. Sand the points and make sure they are gapped correctly, sand the contact points under the cap.

Pull the wire on the cap and coil and make sure it is clean on the ends and set them again make sure they are seated all the way.

Post back i got the exact motor.
 
Are you saying I can't use a conversion kit? I don't think I have a kill switch but maybe, how could I tell? I replaced the points and gapped but still no spark. It's also a brand new wire. I just bought a new condensor and will try that.
 
I have 4 years now the same points, i changed them out just for giggles, the old ones are still in my tool box onboard with the old condenser.

I gave my opinion i would not convert.

3.0 dist est

If anything i would change out the whole dist.

So with the battery disconnected, you cleaned all the connections starter and all ? You cleaned the coil connections ?

You cleaned the main ground " follow the neg cable to the back of the bell housing "

Test the coil with a ohm meter 0 ohms means a new coil. Any auto parts store has them.

Ok another thing i would try is run a pos wire straight from the pos lug on the battery to the pos side of the coil and start the boat.

If it starts, then it ain't the condenser, points, wire or coil.

You will need to quick remove the jumper wire, or the motor won't shut off.

Post back.
 
Update - I replaced the condensor and she fired right up. I have a suspicion though that I may have found the cause while replacing the condensor (due to previous owners wiring) that may have played a part. I know chiefalen that you said you wouldn't convert, I'm just like a little kid though and have to ask the why. I have no need to replace the entire distributor but everything i've read in the meantime claims that a conversion would smooth out the idle, give a little more power and improve the fuel efficiency. At 4.30 a gallon these days I'm trying to save every way I can!
 
If you do it then why not do it right, the kit i posted has everything in one box.

Me, leave it alone i can have the setup for free to convert still on my friends shelf. My boat runs good.

I'm gonna take a guess something inside the cap was touching something it wasn't supposed to. Or the previous owner ran a wire that wasn't a resister wire.

Don't keep it a secret.

I mean this i wish you nothing but good things and success in all your endeavors.

If at any time i can help you in the future just ask.
 
No secret, they had just wired an additional wire to the ignition coil from the accessory switch I think so they could start it in case they lost the keys in the drink. I think that may have been loose at the coil and when I replaced the condensor, i also tightened all the contacts. Unfortunately, I didn't try starting it first to see if it was the tightening of the contacts that needed to be done so I may not have needed to replace the condensor at all.

My biggest concern now that it's running goes back to the original question, why over the last 3-4 years do I need to replace the points each year? I never replaced them for the 6 years that I first owned the boat and it would start up every spring no problem.
 
I did away with my points about 10 years ago for Pertronix first gen conversion and so far no issues. I check my timing and advance every year just to make sure things are still in spec.
 
My thoughts would be that moisture is the culprit and/or the condensor taking in moisture, and that sanding the contacts is unnecessary.
A moisture displacement spray chemical may work here.

If you insist on sanding contact points :mad:, use extremely fine emery paper, and it can be glued to some sort of backer board... making it ridged such as a fingenail board.

I'm not a fan of the Pertronix Hall Effect conversion kits, but it would certainly solve this issue.
Do it.... and you won't have to look back! :)


Aside from this issue, your 1984 ignition distributor advancing system is no doubt showing signs of wear.
When you set BASE advance, I'd suggest that you go to the next step, and check your TA.... (total advance)...., and make sure that it's within specs.
All too often even well seasoned Marine mechanics will set BASE advance only, and then walk away.

.
 
Last edited:
When I was in the business I did at least 300-500 4 cylinder boats a year every spring. They were all point ignitions.
We replaced the points, rotor and condenser in every one of them!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Each and every year.

I would have 3-4 1 gallon zip lock bags full of the old stuff each year.

The reasons are,
1. the minute you start the engine the points start to wear out. They arc and arc and arc and pit.
2. when a point ignition sits over time moisture causes a black oxide to form on the points surface this blocks electrical continuity.
3. maybe the tune up parts you are purchasing are lesser quality then in the past. We used NAPA parts ONLY!
4. do you add a bit of grease on the main shaft where the points rub?? if not you are wearing out the plastic as well as the points them selves.
5. and the most important!!!!!!! This is your boat, you want a trouble free summer, WHY WOULDN'T YOU WANT IT TO BE AT ITS BEST RUNNING CONDITION FOR THE COST OF ~ $25-$35 A YEAR?????????

Spend the money and convert it. One time and you will NEVER have to do it again.
 
LOL you guys don't snoop through your wive's stuff much do you? If you're going to deal with points and file them down every few months then your wife's nail file emery boards, they are perfect for the task at hand.

BUT in my opinion, dump the points and condensor and go for the pertronix. Ps and Cs are the absolute weak point in the ignition system. If I never had to deal with them again I will be a very happy backyard mechanic. As Kghost says that's where he made his money off of boats owners like you. Seems the points fans are just old school guys that resist change. I wish they wouldv'e invented the hall effect ignitor systems long ago. just my $0.02
 
To the OP: you said the previous owner added a wire from the ignition switch to the coil. You might want to check and make sure you only have 9 volts going to the coil. If you have the full 14 volts going to the coil you will eventually be rowing back to shore like I was 2 weeks ago. The coil will get scalding hot and cut out. If you have 14 volts going to the coil, go to NAPA and buy a ballast resistor. It has two prongs: hook up the wire coming from the key switch, hook up a new short wire to + on the coil.
 
I know, I know - 2 years later and now he's posting! After a lot of diagnosing and bandaging, I found many culprits. 1) that wire the previous owner had replace was giving 12 volts. 2) the original coil didn't need an external resistor. 3) I replaced the points with the conversion and found the resistor I needed. I still have yet to replace the resistor wire but using the 12v and a resistor works great. A bigger problem I had as it would turn out was a blown head gasket. Amazingly these engines run great on 2 cylinders! While diagnosing I found that strong spark wasn't necessarily a points problem each year, rather a problem getting very slightly worn points to start an engine with only 2 cylinders properly compressing.
 
Back
Top