Not much spark

[jimmmy]

I have a 1988 Oliver 17 ft with a 1988 Merc 3.0L 130HP. Since we bought it last year we have been unable to achieve WOT under load....can get 2800 to 3000 RPM even after dropping to 17 pitch prop. In neutral can get 4500 RPM no problem. Two different mechanics had the boat last year and after $1500 there has been no change. They checked for exhaust restriction, rebuilt carb, drained and replaced gas, found cracked head gasket and planed head, checked lower unit.<br />We've relaced plugs, points, wires, cat, rotor, condensor and coil. We checked and adjusted the timing to 6 degrees on idle today and confirmed that it is advancing with throttle but we had a heck of a time as the timing light had trouble detecting the spark from the spark plug wire. We were able to get the light to fire only if the pickup was right close to the distributor cap. As you moved the pickup along the wire away from the cap and closer to the plug we lost signal to the timing light. It was this way on all wires. When we looked at the spark on one plug, it appeared to barely spark. Also getting a raw gas smell in the oil (unburned fuel from cylinders??). Any ideas what would be causing my low spark and would this give me low RPM's on load??

 

[rattana]

Re: Not much spark

What is the voltage between the positive side of the coil and the block?

 

[jimmmy]

Re: Not much spark

rattana....how do I check this? Should the engine be running or just the key on?

 

[sculbert]

Re: Not much spark

You need to check your voltage at the - terminal on your coil going to your distributor. It should be around 7 volts with points open. Then you need to test your coil. This is what I would suspect to be the problem. From the tower of the coil remove your spark plug wire. We need to test the ohms resistance from there to the - terminal on the coil. it should be over 10,000 ohms if it says external resistor on the side of the coil. 7700 if has an internal resistor. Now you also need to test the voltage on the + side of the coil. this should have 12 volts if the coil has an internal resistor. If it has a external resistor it should have around 7 volts at the + post. <br /><br />These are very important. I also find alot of people don't understand this and get the wrong coils.<br /><br />The ohms test should be done with the key off and the voltage test with the key on.

 

[rattana]

Re: Not much spark

I would like the voltage a little higher at the positive side of the coil (8 or 9) but like Mercury says.

 

[sculbert]

Re: Not much spark

Rattana your correct. It was late last night. I laways take my boats and convert them to the pertronixs pointless ingnition system "Ignitor II" and put a "Flame Thrower II" coil on them. Just rememebred that it was lower on them. difference between 7 and 8 could make a difference on the spark also. <br /><br />The best solution is to get rid of the points all together like I do. The engines run so much smoother is is incredible.

 

[jimmmy]

Re: Not much spark

Mercury and rattana....<br />The engine has always been smooth...just lacks power and cant get over 3000RPM. With the weak spark and gas smell in the oil, does this sound like my problem?

 

[rattana]

Re: Not much spark

Did you get a chance to check the voltage and resistance yet?

 

[jimmmy]

Re: Not much spark

Nope....won't get back up to the boat until the weekend...unfortunately! My brother-in-law put a new merc coil in last year and it says it needs an external resistor....but I'm not sure there is one?? What would it look like?

 

[rattana]

Re: Not much spark

It will either be a ceramic ballast resistor 1/2" square by about 2" long. Or more commonly a piece of resistance wire in the wiring harness. This wire would splice in between the run signal from your key switch and connect directly to the + side of the coil. When you first replaced the coil how did it run?

 

[jimmmy]

Re: Not much spark

When we replaced the coil last year, we really didn't see any difference!

 

[Bondo]

Re: Not much spark

It Sounds like you have a 1.50/1 ratio Gear set in the upper drive................<br />You Need the 1.98/1s.........<br /><br />Been there, Done that.....<br />You Can't buy a prop Small Enough................

 

[jimmmy]

Re: Not much spark

Hi Bondo....You probably remember my crys for help last summer! I remember that you had suggested the wrong upper gears last year. Mechanics checked this out and ruled it out. We did notice the weak spark last season and again this season and we're hoping this is the problem. As I mentioned in my post, we can barely get the timing light induction coil to pick-up the spark in the plug wires and when it does, it is only on the wire when close to the dist cap. Checked the timing light on my car and it worked fine along the entire wire. This is one reason we belive the spark is weak. The other reasons are visually just a weak spark and the unburned gas smell in the oil. What do you think??

 

[Bondo]

Re: Not much spark

Well jimmmy,<br /><br />How Fast you can Spin an engine in Neutral, with No Load, is Totally Meaningless.......<br />And, Potentially Destructive to the Motor.......<br /><br />If you have a Weak Spark, You'll have to track it down,+ Find out Why it's Weak...... The Coil Should have fixed that.....<br />Maybe it's time for a 3rd Tech....... Who can do a Through Diagnostic exam...<br /><br />I'm also thinking that a Weak Spark, Isn't going to leave Gas in the base.........<br />This Sounds like a Carb Issue........<br /><br />Maybe a Compression Check,+ Leak-Down Test are in order, to see if this motor is even Capable of creating 130hp........

 

[jimmmy]

Re: Not much spark

Hey Bondo...thanks for the input.<br /><br />I don't make a habit of revving to 4500 in neutral. I know it's capable.<br />I hate giving this boat to another money grabbing mechanic! Last year we had the head shaved and a new head gasket installed. Compression test after showed 135 to 140 in each cylinder. Carb rebuilt and both money grabbers say the carb isn't the problem, the gear ratio isn't the problem and there's no exhaust restriction. I need to find a "good mechanic"! Anyone know one in the North of Toronto area??

 

[Northern Eclipse]

Re: Not much spark

Where north of Toronto...I know a good mechanic in Port Severn, His name is Andrew at Jim Earle Marine, he is worth $75hr.

 

[DHPMARINE]

Re: Not much spark

Just watch out for us money grabbing mechanics.<br />DHP<br />And keep asking our advice <br />Where do I put the (grin)<br /><br /><br />sorry,must have tried to put too many boats on the water this week.I'll try to do better next week.

 

[Bondo]

Re: Not much spark

I've been Wrong before, But ,<br />Go pull the top cap off your drive,+ Count the Teeth on the 2 top Gears..............<br />Then Verify that you have a 1.98/1 set........<br /><br />As far as the motor,<br />It Sounds like you Might have Both a Fuel Issue,+ an Ignition Issue.........<br /><br />Maybe Northern Eclipse's guy, Andrew can Bail you out.........

 

[sculbert]

Re: Not much spark

You need to check the voltages I told you. You will know if you have a resistor in the line to the coil. Remember if you have 12 volts on the coil you need a internal resistor coil. You really need to verify my test I listed earlier. If it all checks out you probably don't have any other problem with the coil. You could have a crack in your cap casuing the spark issue. The gas in the oil is probably from the fuel pump. that could be a problem and cause your system to not run very good. That is another issue you should definitly check. You can remove the pump right after running and see if you are getting gas in the oil.<br /><br />Please check the voltages and ohms we talked about to validate your spark issue.

 

[jimmmy]

Re: Not much spark

A merc mechanic near where I live, has suggested that perhaps the timing is only advancing to a point then stopping, causing my max of 3000RPM's. He has suggested checking the weights and springs in the distributor. What should I be looking for?