Engine advice

Y

Yorkshirelad

Active Member
Oct 21, 2017
132
Stratford
Boat Info
340 Searay 86
454 Mercruisers with v drives
Ray-marine radar and gps
Engines
454 mercruisers
Hi Guys,
Returning from our favourite swimming hole, about a 1 hour ride back to our marine at 22 knots, my port engine started missing while on a plane. I played around With the throttle but couldn’t get the rpms above 3000. Seamed like it was fuel starvation Or electrical, kept on a plane finding the sweet spot. Before I speak to the mechanics this morning just thought I would put fresh fuel and stabilizer in the tanks. Last year i had the plugs, wires and points replaced. Idles fine. Any advice would be greatly appreciated!
Cheers Rob
 
How old are the exhaust elbows/risers?
 
tiaraatya..jpg

You may have three fuel filters on a boat of that age, a water separator, a middle filter, and a small carburetor filter. Could be any one of them. Also, arcing spark plug wires will produce the symptoms your describe. You can see the cracks in the wires when you run the boat in the dark with the engine cover removed. You will see blue lightning coming from the wires where they are bad.
 
sbw1 said:
View attachment 89831
You may have three fuel filters on a boat of that age, a water separator, a middle filter, and a small carburetor filter. Could be any one of them. Also, arcing spark plug wires will produce the symptoms your describe. You can see the cracks in the wires when you run the boat in the dark with the engine cover removed. You will see blue lightning coming from the wires where they are bad.
Click to expand...
Um.....awesome picture!
 
Points don't store well. Your describing ignition issues with (missing). Your points are a year old, stored since last year. I'd clean them and readjust. Then give that a try.
 
Thanks guys, I put in some gas and Sea Foam treatment. I took her out and she ran great! If it happens again then I will assume it’s the electrical components, but thanks again for the advice.
Cheers Rob
 
Yorkshirelad said:
Hi Guys,
Returning from our favourite swimming hole, about a 1 hour ride back to our marine at 22 knots, my port engine started missing while on a plane. I played around With the throttle but couldn’t get the rpms above 3000. Seamed like it was fuel starvation Or electrical, kept on a plane finding the sweet spot. Before I speak to the mechanics this morning just thought I would put fresh fuel and stabilizer in the tanks. Last year i had the plugs, wires and points replaced. Idles fine. Any advice would be greatly appreciated!
Cheers Rob
Click to expand...
 
Replace your fuel water separators if you haven't this season. The Thunderbolt module is also suspect. One good old school technique is to run the engine at the dock at night and look carefully at the engine to see if you see any stray sparks between plug wires and surrounding metal. This suggests bad plug wires
 
Neil Goldberg said:
Replace your fuel water separators if you haven't this season. The Thunderbolt module is also suspect. One good old school technique is to run the engine at the dock at night and look carefully at the engine to see if you see any stray sparks between plug wires and surrounding metal. This suggests bad plug wires
Click to expand...
Picture 001.jpg

It's best to do this while the boat is underway and loaded. Many times bad wires will allow the engine to rev to full RPM if it is not loaded. Load it up and you will see blue lightning when the engine struggles to produce power.
 
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