Strange Change on RPM's - any ideas?


My fuel filters were changed two weeks ago, and it did not resolve the problem.
For me, it is barely noticable whith 1 or 2 people in the boat. When I have 6 or 7, it is much more pronounced.
I have not tried WOT yet. I will Friday to see if I am not reaching 5000 RPM on Stbd, as it should.
 
Has anyone with this problem but a computer to the engines? I think this must be the next logical step...
 
I also compiled a list of other people having similar issues (not just forumula). Any of these items could result is issues...and other people had success at some point or another by resolving these issues.

Ground cable to battery loose
Spark Plug(s) Bad
Spark Wire Disconnected
Fuel Filter
Too much oil
engine in Guardian mode
Crankshaft position code activated
camshaft position code activated
Clear all engine codes
 
Interesting.
Is it coincidental that we are all experiencing this on Stbd, or is there something about this list that is more likely to occur on Stbd?
 
toofast said:
Has anyone with this problem but a computer to the engines? I think this must be the next logical step...
Click to expand...

So, as I stated, my dealer recommended a tune up and new plugs & filters to address the problem. I just spoke with the mechanic. He DID put a computer on the engines at that time and got no codes. Everything seemed fine when he test drove it after the tune up. It did for me, as well when I test drove it.

Then, when I got more people and gear on the boat, I got the same results -- needing to throttle up the Stbd engine in order to sync the tachs. This suggests that, under incresing load, my Stbd engine is losing power.

The mechanic asked me to run the boat @ WOT to see if the Stbd engine will achieve max RPM equal to the Port engine (5,000 RPM). If it does not, then, for sure, we need to do a compression test and leak down test. I will be doing that this weekend. More to come. :-\
 
Seas-The-Day;

I also talked with a lead tech at Raylar (builders of 496 engines)...they confirmed we are right on track. If you are not getting WOT of the STBD engine and you've done the rest, then a compression/leakdown is the exact next step!

Let's all keep each other informed!

Best of luck and hoping for a dry weekend!
 
No I have not modified...

It is something I am considering...but not for a while...plus I have a PC, so not sure it is worth it.

Might save it up for my 400SS
 
So, as requested by the mechanic, I took the boat out at WOT yesterday and both engines met or exceeded the 5000 RPM's.
That would, at least, suggest that the cable linkages are OK.

The only problem is that I am experiencing a greater loss of power on my Stbd when under a greater load (more people and gear on board) and I was only able to go out alone yesterday. It will be at least next weekend before I can get 6 or 7 people on board and try again.
 
I experienced a large difference in stbd throttle, of a couple inches, to match rpm last year, and it turned out to be one spark plug.

I do have small differences of about a quarter inch or so depending on load, trim and weather, normally. Stbd needs a little more at higher rpm's but less at low rpm's suggesting linkage. I too want to try the WOT though, sounds interesting.
 
Would our drives handle the Raylar torque and HP? Don't think I would try it with mine, but the Volvo Penta DPH would surely do the trick. That would be an interesting combo in a few years, but here's betting I won't be in the 34PC at that juncture.

Got your anomaly figured out yet TF? My bet is a fouled plug or plug wire, but I'm certainly no authority on this sort of thing.
 
V1rowT8 said:
Would our drives handle the Raylar torque and HP? Don't think I would try it with mine, but the Volvo Penta DPH would surely do the trick. That would be an interesting combo in a few years, but here's betting I won't be in the 34PC at that juncture.

Got your anomaly figured out yet TF? My bet is a fouled plug or plug wire, but I'm certainly no authority on this sort of thing.
Click to expand...

As for the Raylar...our drives, meaning the normal BIII should handle the upgrade from 375HP to the equivilant of the HO, 420 or so...but honestly it is probably not a great idea...thus why I am only "dreaming" about it. Maybe someone else can chime in as well.

As for the RPM Difference....well I checked everything I could...Spark Plugs, Wires (both sides), Fuel Filters, Batteries Grounds....everything seemed perfect.

Went for a run...same problem. EXCEPT this time I notice my drives seem to be out of trim...meaning the PORT drive was "higher" then then STBD drive...if I trimmed them manually I seemed to get close to the same RPMs...but the lake was rough, so I really could not tell for sure.

But I do have some glimmer of hope that maybe it is not engine related after all...I will have to hope for a small lake and do some more testing.
 
I have the B-III X and run with 496 Mag HO (425 HP) and it does not seem to be a problem. However, over the 496 Mag HO's, I think they recommend the Bravo III XR.
 
Well then maybe I need to supress my dreams of an engine upgrade...us mortals ;) with the 496 mags only have the regular BIII and not the BIII X drive.

Oh well...

To keep on this thread....

To all those having issues...if the do it yourself engine stuff comes back negative...I would really recommend measuring the drives as Castines indicated earlier in this post...I will not be able to get to mine till hull out...but I really think before we waste money on computers and compression testing...check what we can first.

I will keep checking of course, and keep everyone informed.
 
Good point, too fast.
I did that, as well, on Saturday.
I measured the pistons from mounting bolt center to mounting bolt center on both sides of both drives and came up with 19" on all four.

(Previously, my Port drive was higher by about an inch, but I was advised that air can get in the line and cause a difference. Before measuring, I am advised that you need to fully raise the drives all the way in trailer mode, and then drop them down. You should be able to get an accurate read then.)
 
Volvo DPH or DPR drives would be awesome on a 34PC.

Wish Volvo would offer those drives with gas engines especially like the nibral props with the DPH drives.
 
Seas-The-Day said:
Good point, too fast.
I did that, as well, on Saturday.
I measured the pistons from mounting bolt center to mounting bolt center on both sides of both drives and came up with 19" on all four.

(Previously, my Port drive was higher by about an inch, but I was advised that air can get in the line and cause a difference. Before measuring, I am advised that you need to fully raise the drives all the way in trailer mode, and then drop them down. You should be able to get an accurate read then.)
Click to expand...

Seas---

I think there is possibly another step or two as well.

Meaning, you measured at full drive trim down. What if you use the "dual trim button" and trim it up to normal operating trim on plane. Are the measurements still exactly equal? What if you then trim back down, are they equal again?

I think what might be happening is that because for unknown reasons, the drives do not perfectly move up and down in unison...after two or three up and downs...maybe we have a big difference? Does this make sense?
 
Castines said:
if one is drive is different then the other, then you have a calibration problem from the sensor on the drive and it needs adjustment.
Click to expand...

Quick follow up...if the measurements are off....is this something that can be adjusted "in water" ? For example, if one drive is 1" lower than the other...do I move one down or the other up? Is that even possible?

Thanks again!
 
My drives do not move up and down in unison. My Port raises faster than Stbd. I always need to manually trim Stbd further after using the "dual trim button" in order to get my trim gauges equal.

When equal, my drives are within a small fraction of an inch w/in the same trim distance (which, by the way, is only about an inch or greater than when they are fully lowered).

Now, with the throttling issue, I am finding I need to trim Stbd a little bit more in order to get the throttles and tachs synchronized.
???
 
Does anyone know on the smartcraft sc5000 display showing trim angle there is only one screen, is it showing the port or starboard drive angle?


TIA
 
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