tm29

sorry also there are no tabs or p/u under boat etc etc under either side

InXS

Airpacker is correct about making a drastic effect in handling when you change props from turning out to props turning in. You also metioned having a bent prop shaft, that you fixed. If could be that the bottom of the boat was damaged when the prop shaft was bent. Sounds like you have check quite alot, I would also check the hull for damage or damage that was corrected and is still not quite 100% spec. IMHO

dirtyplumber

try one engine at a time and note the difference even just to listen
could that slow engine be leaning out .swap,fuel pump,,injectors(you'll need new o-rings),maybe a bad antisiphon or vent .swap ecm, is there a knock sensor i'm not an expert on efi.how did the plugs look/differ.check plug wires with ohm meter

tm29

the bent prop shaft was from previous owner it was not in route at all he backed into a dock and bent the shaft didnt even scratch the skeg at all and looked again at the hull and seen nothing at all

as far as plugs and all the ones I took out all looked real good the port side looked a little fatter than the stb side but not to bad

Im just running out of things to check at this point not sure if I need to locate a scan tool and see if any codes etc etc.

mcollinstn

If you haven't done wires, DO THEM.
You only THINK you can't hear a miss. Takes a couple of times to hear the change when you drop a cylinder from a weak wire (it fires reliably until you get a good load on it).

Verify tachs. Get a calibrated snout tach (push a rubber cone into the center of the crank while spinning).

You mentioned earlier that one reved to 5100 when trimmed max. Are you trimming to the limit switches? Don't do that. You may be aerating the prop and losing bite, letting the revs climb. Do all your tests with the drives at the same exact angle.

tm29

I will do wires for sure and go from there. Im trimming not to max but just where the bow comes up and cruises real good.

tm29

The only reason that made me think it wasnt wires was all the engines I ever seen when ever wires went bad and you were under a load the rpm's would jump around some. the lame engine in the boat is dead steady on the rpms. But I will take your advise for sure and change them just for peace of mind if anything
thanks everyone for help

Twig111

I just reread this post - originally you could sync engines if you reversed props. I wonder if they would sync with your new props? That would have to be a clue. Maybe a hull problem like a hook causing one side to bite harder than the other.

At lower speed and WOT, do you still see a 300-600 rpm difference? Hole shot etc. Someone mentioned running one engine at a time. What are your max rpms under those conditions?

tm29

No I havent tried turning the props in yet. maybe im on the wrong track here. I was thinking this was going to be a engine issue. But after reading some replys it seems people are thinking it maybe the hull. any way of checking the hull. still maybe an engine issue though. I was wondering if anyone else has ever ran into the same issue

blue thunder

I switched to spinning in last year. What a difference. The boat behaved entirely better, particularly at WOT. Currently I have one engine making more power than the other (9.5:1 vs 8:1 comp) and get a variance in engine rpm or about 200rpm. I can even the rpms using the trim. You should be able to as well if it is an engine issue. You should get running, trim it out the way you alway do, note the rpm variance, then stop and visually check your drive positions relative to one another.

BT