Hello all and thank you for what...

[Lizzy]

Hello all and thank you for what I have read and learned from your answers.  We are new to boating and bought a 2006 340 Sundancer with Mercury 8.1’s.  She’s very clean.  Looking for advice on an intermittent no start / stall of our port side motor.  I can not stress how well maintained the boat is.  The prior owner replaced many items just to be ahead of things.  Fuel pumps were replaced 2/3 years ago.  Fuel solenoids were replaced too.  (Will not bore you with the whole list of new parts) We replaced the fuel filter on the port side - thought that fixed the issue.  Our mechanic tightened a slightly loose harness which when he moved - she stalled.  Last night- no start - cranked (full fuel tank). We squeezed some hoses and 5-10 minutes she started and ran beautifully.  Went out.  2/3 hours later about to head home- started.   On way stalled.   10-15 minutes later started.  Anything you think I can look for will be appreciated.  I will do my best although when our mechanic has time- I will ask for his assistance.  Unfortunately the intermittent issue does not make this easy.  Picked he up end of last season and most time she started and ran beautifully.  

[wingless]

Welcome to the forum.

The boat will only go when it wants. Please learn who is in charge and get w/ the plan.

The issue is VERY easy to diagnose. There are two engines. Do the same checks on each to see what is good, what is bad.

Using a DC voltage meter, black wire connected to the engine block ground, measure DC voltages using the red lead.

The Red / Purple wire should have +12VDC when the engine is on. Measure on the rear of the circuit breaker. The Red lead from the circuit breaker to the starter should also have that same +12 VDC.

The small Yellow / Red lead to the starter slave solenoid, up high on the engine block should have +12 VDC when the starter switch is pressed.

The thick Yellow / Red lead on that same starter slave solenoid should also have the same voltages.

My 100% speculation guess is the starter slave solenoid has gone bad. My spare parts arsenal includes two of these, just in case.

Another 100% speculation is that the high current leads will all be MUCH happier if they are disassembled, inspected, cleaned, reassembled, properly tightened, then protected w/ liquid rubber. Please remember to disconnect every battery negative terminal before performing this service.

[Lizzy]

Wow. Thank you for the detailed response and information. First I will need to pick up a DC volt meter. Next day off - will take a whack at this. Thank you again. Dave & Liz