So, I decided to change the spark plugs, wires, caps and rotors myself and see if I could take care of the issue. The vessel was in for boat paint about a year or so ago and the shop changed the cap, rotors, wires and plugs on Port side engine to chase after a mishap that they caused....don't want to get into all of that, but I figured everything out and fixed it myself after getting it back and everything has been fine since. This vessel has never had a single hickup at all while underway before or after the shop had it.
Anyway, I recently changed both caps, both rotors, all wires and all spark plugs. For some that might be interested, I took resistance measurements on the aftermarket wires that the shop used VS the stock Volvo Penta wires and have all of the readings below. Not that this setup doesn't work great below 4,000rpm and such, but just something I noticed is all:
Longer to shorter wires | Resistance Measurement | Aftermarket VS Brand New Stock Wires:
14.82K VS 1.52K
12.33K VS 1.14K
11.06K VS 1.1K
9.2K VS .93K
8.90K VS .86K (Coil)
Old Volvo Penta Wires that came out from Starboard side (Over 3 years old) Resistance Measurements:
1.59K 1.58K
1.34K 1.37K
1.13K 1.14K
.92K .92K
.75K (Coil)
Port Side Cap and Rotor New VS Old - This side was replaced about a year ago by a shop
Starboard Side Cap and Rotor New VS Old - Over 3 Years Old - Still Volvo Penta Wires
Old Caps, Old Rotors and Old Plugs
Old Caps and Old Rotors
New Spark Plugs, New Wires, New Cap and New Rotor Installed
Filling up the tanks before testing
Another Carver at the Marina
Bad day for testing, but did the initial test to only 4,300 - 4,350 range with full tanks and pretty heavy winds - boat has never been above 4,000rpm previously and was working great as it easily went to the 4,350 range no problems at all! Weather was not the best with all the winds and also wanted to do baby steps to check everything out first too so stopped at 4,350. Fox Marine Data Logs showed 68% throttle. Followed the data all the way up to 4350 and is in line to hit 5,000rpm max. I would not personally run a boat engine that high for every long, but just would like to know that it can do its max rpm.
Important Note: MPG is multiplied by 10 everywhere to make it more graphical.
Before and After Maintenance - Did a bit better MPG in the midrange and of course a lot better in the upper, but this is also comparing 1/3 full tanks and great weather to 100% full tanks and also terrible windy weather out, but mainly the boat would not go above 4,000 range before the maintenance and now it easily goes above 4,000rpm no problem. Also to note....I have been testing trim tabs as well and they were still deployed down a bit too in all testing in the graph. Since I can now test above 4,000rpm I can now see that it is very apparent the MPH starts going up pretty good when I start clicking the trim tabs upward, but the midrange is or course better with the trim tabs down for efficiency. For MPH and MPG tests in the upper range I need to finish testing with the trim tabs all the way up and do another graph as I think it will increase MPH more with no RPM changes as the trim tabs were still down a bit.
Beautiful Day out, but chilli!
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