1986 mercruiser 4.3 cranks but wont start


Old 05-06-05, 06:01 PM
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1986 mercruiser 4.3 cranks but wont start

i have a 1986 mercuiser in a starcraft. engine wont start !

The boat has been sitting for five years. It was professionally fogged before it was last started. I put a battery in and the engine just clicked. Long story short and I changed the starter and now it just cranks and wont start. I smell gas so I think its getting fuel.

I pulled a plug and shorted it against the block, turn the engine over and didnt see a spark. I then pulled the dist cap and cranked the engine and didnt see a spark on the points. Someone told me to put a spark plug on the coil wire and that I would see a constant arc.. did it and no arc..;

I 'm looking for some guidance on testing the ignition curcuit..

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Old 05-08-05, 12:49 PM
Join Date: Nov 2004
Posts: 74
Failed start

I never found your test for spark to be always reliable. I use a simple test lamp that looks like a screwdriver. Rotate the engine so the points rubbing block is on a high cam point. Ground the test light clamp and touch the point of the test lamp to the points in the distributor. Rock the distributor slightly so the points just open and close. If current present the lamp will go on and off.

After sitting so long corrosion on any connections will certainly be an issue.

Start at the distributor and remove and clean all contact sufaces of wires leading to the distributor and to /from the coil. Any ground wires too. Coat with dielectric grease before re-fastening the connections. (vaseline?)

You could use the test lamp to probe any wire in the open circuit to see if it has current.

See also, a posting further down by 'onegizmo4u' titled '.. ran, Won't run'.

Old 05-09-05, 04:25 AM
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Thanks and some constructive input

Thanks oldjoe,

That is pointing me inthe correct direction and is very helpfull. Most of all, thaks for the reply, I did think anyone was going to help me on this !

I'm still looking for a complete trouble shooting guide for theignition. such as:

1) battery check...
2) key switch check
3) check points
4) with test light check to see if the safty swithch are working by doing..

something like this would answer about 50 recent question in this fourm...

Ive been looking for this for days.. I love it !! I have to tell you, I'm a first time boater so I do not know the ropes. please take the following as a observation not a critism.

Keep in mind that I'm know as a good trouble-shooter in my field. I can see why people have so many problems with boats if they use a hunt and peck method of resolving technical issues. I've been reading the postings and think that if someone normalised the problems people are having they would find several very distictive areas.

If the technical expersts on the site would write comprehensive testing guides for each area such as what I'm asking for with ignitions, the users would have quick repairs and save a bundle not buying parts that were not needed.

you guys could just point people tyo the articles AND the learning experince for people would be endless// In addition, people could print this stuff out and keep it on their boats to trouble shoot with in a difficult sutation..

just my two poorly spelled cents..


Last edited by lchiango; 05-09-05 at 10:12 AM. Reason: can't spell to save my life
Old 05-10-05, 08:04 AM
Join Date: Nov 2004
Posts: 74

The info you seek is included in a SELOC engine manual for your boat.

I ordered one from http://www.marineengine.com/

They also have other manuals that may also pertain to your boat. They provided same day shipping. I found the manual very complete.

The manual does not always get you to the core of a problem. Moreso a good reference for teardown and reassembly. For instance the manual would not suggest a test lamp. These forums enable access to someone who has a direct solution - so a novice in mechanics can obtain the insight necessary to readily understand the nature of the area in question. This should relate well to your experience in your own field. The book is available ... but can we absorb all of the material in the chapter readily? Not likely, due to use of unfamiliar terms, and related but additional material to add to the burden of the problem.

The ignition points break a primary circuit that allows a secondary circuit
(built up as a hjigh voltage charge on the coil), to release as the spark to the plug thru the pointing device the distributor cap. The high voltage gets to the cap from the short wire from the coil.

The usual problem I find is that the cam rubbing block on the points wears down, thereby changing the point gap setting, which in turn affects the timing of the electric charge to a plug. Rather than regapping the points, I ALWAYS replace the points set (and the worn down rubbing block). The gap
in the points at any high cam point I believe allows for the time for the coil to recharge itself. Points 'burn' i.e. transfer small amounts of metal from one side to the other due to the arcing of the low voltage primary circuit. the condenser absorbs some of the primary cicuit charge to reduce this 'burn' effect.

Points are gapped at a high cam lobe according to a setting for that particular engine. If unknown try .020". the engine should start. The engine timing is then fine tuned by using a timing gun (Strobe light) to see a mark on
the crank pulley that coincides with a fixed marker on the engine block. The distributor cap is rotated left or right slightly to obtain this alignment.(The slight rotation in effect adjusts the point at which the rubbing block touches the high point on the cam). The mark on the crank pulley is a chalk line you make there at the required number of degrees in advance of top dead center of the compression stroke of cylinder #1, i.e. maximum compression for firing referred to as BTC. The degree markings are ETCHED on the crank pulley but require a chalk line to be visible under the strobe light.

I use a cheap multifunction tester from Radio Shack. They are now digital as well as analog.

I use the ohms test for line continuity, ie to test to ensure a wire is not broken or does not have too high resistance! Spark plug wires are tested for resistance and should all have similar readings.

The test of a battery would be DCV dc volts and should be slightly higher than 12 volts. If testing the charging value of the alternator the voltage read should be (I think) in excess of 12.7 v.

If an older engine perhaps change the fuel pump before taking it out! The water pump should also be considered for replacement for the same reason.

In my autos I use for 90,000 miles, then simply replace certain parts. At 60mph that should approximate 1500 hours of use. A fuel pump does not give prior waring of failure, but the water pump may leak, squeal slightly like an unlubricated belt or the pump bearing has a lot of play.

Marine ignitions may be different than automotive so always refer to your marine manual for ignition switch information.

The clicks you heard seem like bad electrial connections at the battery,, whereby the solenoid was not getting enough current and only 'clicked'.

Since the engine just goes 'round and round' unless a peice simply breaks or wears out, the common problems should be carbueration or electrical .....

Safe boating...


Last edited by oldJoe; 05-10-05 at 10:12 AM. Reason: Add info

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