bloohound guide to boat motor trouble shooting.

[bloodhound]

*motor doesn't run.
-fuel issues
1. try to start with starting fluid. if it doesnt start go to spark issue. if motor starts but dies very fast will only run if starting fluid is sprayed in carb, motor needs a carb clean/rebuild.
-spark issues.
1. motor has no spark take it to a shop, or buy a manual and follow the step by steps for your motor.
*motor runs, poorly.
1. do a spark and compression check, all cylinders should have spark and all cylinders should be within 15% of each other. example.. 110,115,112,118, bad example 110, 50, 113, 120. if everything checks ok, carbs is most likely issue and need to be cleaned/rebuilt.
2.if missing spark on one or more cylinders take it to a shop or buy a manual and follow the steps. 

following these steps will allow you to trouble shoot almost everything.

[Soady]

Three items needed for combustion: fuel, oxygen, ignition source. Remove one of these and nothing will happen. Within each of these three components are various delivery methods (peripheral systems)  that provide each one to the combustion chamber so one must become familiar with each delivery system and evaluate each delivery system to make sure each system is operating within specifications.

In addition today's modern intelligent systems have safety lock outs to prevent damage to components as well as the motor itself so all peripheral systems must be doing their job as well.

Just today I was stumped by a 1987 Volvo AQ131D motor not wanting to start from the ignition switch. Both batteries were fully charged, spark was evident, fuel was evident to a point. The fuel filter was filled and changed out which let the motor start from a remote starter switch connected directly to the starter, bypassing the ignition. The motor ran for a bit and then died-due to loss of fuel. Loss of fuel resulted from the boat being attached to the tow vehicle which was pointed slightly down hill even though there was ten gallons go fuel in the boat. Spark loss was due to a safety lock out switch in the shift control locking out the starting mechanism. After moving the tow vehicle to allow the boat to sit level as if on the water and allowing the fuel to reach the pick up tube I then adjusted the shift lever to allow the safety to make up the contact allowing the ignition system to fire and boat motor ran perfectly.

So even a boat with modern intelligent 1987 systems in place one really must think through all possible scenarios in order to truly understand what is really happening and what is not happening . BTW I had all the manuals and the entire web at my disposal and they did not help in the least, the only thing that did were the three components fuel, oxygen, and combustion and how the peripheral systems interacted within each other.

[bloodhound]

its called a neutral safety switch. there are 2 on on some stern drive boats