.....so it is in limp mode (reduced power) because of a fault code.....makes sense so you aren't stranded on water. Funny they don't add "check engine" light on dash so you are aware it needs error diagnosedYes there is a diagnostic port on top of Mercruiser I/O's. On my 4.3L it was near the distributor/cap. Your Mercruiser engine guardian system is performing exactly how it's supposed to. It's limiting the RPMs preventing damage to your engine. With the diagnostic scan tool it shouldn't take them long to figure out what's up. You'll be back on the water in no time. Be positive. There's plenty of summer left!
Oh yeah those plugs arent cheap. I'm assuming they're iridium??? But they perform well and last long. Hope this solves your problem......Update: the Mercury dealer finally hooked it up and said it was throwing numerous engine fault codes. His initial diagnosis was fouled plugs. He said that my engine has a tendency to that. $425 (plugs $180, the rest labor and tax)
Haven't had it out on Lake yet, but I ran it in my driveway and as the dealer said, the engine was much smoother. MUCH smoother!
In the driveway it used to sound like a dragster at idle... loud brap brap brap. On the water, I always thought it was loud. I now realize this was a lot of misfires. This is my first motor boat and I bought it used, so I don't have a basis of comparison.
Now, she just hummms!
If Hurricane Hanna is gone in time, I may try to get her out tomorrow for a test run.
Also, I bought the Vesselview Mobile and installed it. Seems pretty cool. Looking forward to trying that out also.
Nothings cheap when it has “Marine” in front of it (except maybe me) When I had my old jet boat and was constantIy changing plugs, I cross referenced my “marine plugs” to regular and price was like 75% less ..Oh yeah those plugs arent cheap. I'm assuming they're iridium??? But they perform well and last long. Hope this solves your problem......
Yup used to do the same in our first boat. Back then the AC Delco "marine" plugs were $6 or $7 a piece. Regular automotive ones were a dollar. Put them together and they were identical! Same with the oil filters......Nothings cheap when it has “Marine” in front of it (except maybe me) When I had my old jet boat and was constantIy changing plugs, I cross referenced my “marine plugs” to regular and price was like 75% less ..
Wow at least 6 years without changing the plugs. I bet you won't do that again. While you are at it have them check the distributor cap and spark plugs wires. Especially if they are the originals. Also put a can of Seafoam in your gas tank. Clean those fuel injectors.......Have you changed the impeller?Thanks. As I said, this is my first motorboat and we bought it used, so we have no baseline for comparison.
We were thinking today that it has never run this well. The plugs were possibly bad from sitting unused for 3+ years before we bought it, and kept getting worse in the 3 years since.
Today, during 2 hours of run time, it seemed to get smoother. As Jack M said... maybe some high speed blow out helped?