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HELP!! 1987 75 HP 3 Cylinder Won't Fire

M

mkjprice

New member
Some back story - I have only had the boat for about a year. Never really have had a successful trip with it. 1st Trip - motor ran OK but not full power - and noticed transom was soft. Took the boat out of commission and rebuilt the transom.

Next trip after transom - motor started fine and once out of the no wake zone, it would slowly lose power throttle position the same, until cut off.

Same every trip after that.

Things I have tried,

Compression 90 psi on all three cylinders. Replaced fuel line, fuel bulb, anti siphon valve, rebuilt carbs, new fuel lines and filters. New spark plugs, also rebuilt fuel pump. Running fresh gas. It is a 2 stroke but the oil injection system was removed prior to me getting it. I run 50:1 premix. Tested spark on all three cylinders with the spark plugs arcing to the block. All look good.

Motor will crank, but will not fire. With water collar on - I cranked it yesterday and it backfired out the exhaust, and nothing since. Looking to see if there are any more suggestions.

This motor is on a 1986 Fiberglass fish and ski boat, so not looking to spend a ton of money on it, but hoping for some suggestions. In Rural Utah, I cannot get anyone to look at it because it is too old.
 
I have a '85 - 60hp 3 cylinder, I am assuming that these are fairly similar. I am guessing but would start looking at the stator and the wires coming from the stator. You will probably need to pull the flywheel to get a look at them all. (buy the Merc flywheel puller off ebay for about $25 - worth every penny). The insulation on mine was crumbling off and possibly shorting out, not fixable. There are two sets of ignition winding in the stator. One for low speed and the other for high speed. The third set of windings in the stator is the battery charge windings. You will probably need a DVA to test the stator for correct operation if the wiring looks good.

https://smile.amazon.com/dp/B0093U3...-smile-us000-pcomp-feature-scomp&ref=aa_scomp

here is a link to the CDI troubleshooting charts

https://issuu.com/cdielectronics/do...eb.2013_issuu?mode=window&viewMode=doublePage

Hope this helps.
 
WOW! that is a great resource, I will look into that also. Weekend is coming up and I should have some time to look further.
 
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