Starboard engine occasionally loses thrust at higher rpms when cruising

Was this boat re-powered? sea Ray did not offer an 8.1 for your model year standard power was a 5.7 350 with an optional 7.4 let’s get back to the basics find out exactly what model engine you have in there...
 
Not sure where yo get your information, but most 2006 340s we looked at when purchasing, if not all of them, had 8.1s with V drive or 496mags with Bravo IIIs. I can assure you they are the original motors, with 1025 hours each and the outdrives were replaced 2013 for the Port Side and 2015 for the stbd. So no need to get back to the basics, I know what motors I have.
 
tiara in the snow 01.JPG
I see you replaced the coils. Did you also replace the spark plug wires at the same time? Running the boat in the dark with the ER hatch open (if that's possible with your set up) will sometimes show you just which wires are bad. My 370 Express was hard on plugs and wires. When it started to exhibit the symptoms you describe, there was a blue lightening storm going on in the engine room. New wires, and things returned to normal. This sounds like an electrical issue to me.
 
electricaldoctor - totally agree. Replacing them is on the agenda as they will not hold a charge. Will rule out the bad batteries ghost, and they are overdue.
 
Korkie said:
Not sure where yo get your information, but most 2006 340s we looked at when purchasing, if not all of them, had 8.1s with V drive or 496mags with Bravo IIIs. I can assure you they are the original motors, with 1025 hours each and the outdrives were replaced 2013 for the Port Side and 2015 for the stbd. So no need to get back to the basics, I know what motors I have.
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Relax buddy This was not directed at you it was directed at the OP he has a 1995 330 Sundancer
 
Korkie said:
Not sure where yo get your information, but most 2006 340s we looked at when purchasing, if not all of them, had 8.1s with V drive or 496mags with Bravo IIIs. I can assure you they are the original motors, with 1025 hours each and the outdrives were replaced 2013 for the Port Side and 2015 for the stbd. So no need to get back to the basics, I know what motors I have.
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After all that’s what this thread is about isn’t it? ...
 
OK My bad. Sorry about that. It is hard to decipher exactly who is responding to what when there are several inputs on topics in a thread. I usually put whom I am responding to in the post.
Again - My Bad. Really didn't make sense that joeyleggz wouldn't have already known that.
 
Korkie said:
OK My bad. Sorry about that. It is hard to decipher exactly who is responding to what when there are several inputs on topics in a thread. I usually put whom I am responding to in the post.
Again - My Bad. Really didn't make sense that joeyleggz wouldn't have already known that.
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No worries we’re all just trying to help each other out that’s the whole purpose of this form normally I do reply to a specific post ,Caught off guard this time
 
OK, now that we are back on point, has anyone heard back from Guuci lately? I'm not 100% sure that he wants our assistance anymore as he has hired a marine mechanic to solve his problems. It would be nice to know how his situation was resolved though.
 
Thanks for the plug wires suggestion. After batteries, if ghost still present, will try the running in the dark trick. Makes sense. The plugs and wires were only supposed to be 3 years old when we purchased. Have changed plug twice, but never wires.
 
electricaldoctor said:
8.1 Mercruiser?? Why does your sig say Twin Mercury 350?? Which is it?
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Sorry, 8.1 Mercruiser 320 hp, did not know the distinction between outboard (Mercury), inboard (mercruiser).
 
electricaldoctor said:
OK, now that we are back on point, has anyone heard back from Guuci lately? I'm not 100% sure that he wants our assistance anymore as he has hired a marine mechanic to solve his problems. It would be nice to know how his situation was resolved though.
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Thanks, the marine mechanic is still trying to solve it, he is saying that the heat sensor might be the problem, causing the engine to run at closed loop, since the indicator shows, it is not heating to the normal mode 130-170
 
I relayed the suggestions on topping up the batteries (batteries are less than a year old but has not been topped up) and plug wires,let’s see what happens.
 
Korkie said:
Have the same motors (496 mags) and been chasing the same type of issue (all last season). Would be cruising at 3400 and the rpms would drop 2500-3000 briefly (just long enough for you to feel it) and return to the 3400 withing a couple of seconds at most. It is always the same amount of drop but would do it more and more often the longer we were out. End of last season had transom assemblies done and the mechanic also helped me chase this ghost around when we went out for test run after transom assemblies done. Had the computer hooked up and was getting some voltage variations to different sensors. After some discussion, he asked the age of my batteries. They are more than 4 seasons old and if left of charge for longer than a few days, will not start the motor. After looking at them, they are bowed out on the sides and his first instinct was to replace the batteries (since they are due anyway). So . . .Plan is to replace batteries for that motor this spring and see what happens. He explained that the Mercury computers are very voltage/amperage sensitive and just 1 poor battery can cause really weird stuff, just as this.
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This seems to be the exact same problem, very frustrating indeed.
 
electricaldoctor said:
OK, now that we are back on point, has anyone heard back from Guuci lately? I'm not 100% sure that he wants our assistance anymore as he has hired a marine mechanic to solve his problems. It would be nice to know how his situation was resolved though.
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Not resolved, still interested in hearing other suggestions anyone might have, will be sure to let you know though, if we manage to resolve it.
 
sbw1 said:
View attachment 65768 I see you replaced the coils. Did you also replace the spark plug wires at the same time? Running the boat in the dark with the ER hatch open (if that's possible with your set up) will sometimes show you just which wires are bad. My 370 Express was hard on plugs and wires. When it started to exhibit the symptoms you describe, there was a blue lightening storm going on in the engine room. New wires, and things returned to normal. This sounds like an electrical issue to me.
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Did not replace the spark plug wires yet, next in line..
 
joeyleggz said:
Was this boat re-powered? sea Ray did not offer an 8.1 for your model year standard power was a 5.7 350 with an optional 7.4 let’s get back to the basics find out exactly what model engine you have in there...
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I will ask my mechanic.
 
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