260 not turning r's

[20cc]

i posted here a while back about my merc 260 not turning the rpm's it use to,i tryed out some of the things that was mentioned but still no success, so here's the deal: i have a 20cc bullet and had my bottom pad redone, it got water in it and the bottom started to flex and the boat would not lift, so i had the pad redone and the transom redone while the boat was apart, since I got it back it want spin the r's it did, i was turning around 8200 running around 95, now it will only turn around 6900 at 87, I can run loaded to fish with 2 people and run empty by myself and it runs the same rmps at the same speed 87, the motor runs fine, no skipping, its feels good and strong, heres the deal about the motor, the top cylinders are clean as a whistle, middle half & half and bottoms mostly black, I thought it was a motor issue so I : changed out injectors, coals, switch boxes, tryied out another ecu, spark plugs, tryied a prop 2 pitchs smaller,checked the firing, compressions real good, made sure vacum hoses,checked filters, i've done came this far so i'm willing to try anything else,THANKS

[D.B.S]

Did you check the leak down? How many hours on the motor? Is the boat heavy now that you had it fixed?

[patchesII]

You've covered just about all the bases with the motor. I would definitely do a leakdown and also check the bottom of the boat for straightness. If the bottom was a little tweaked when they added the glass inside they could've preserved that hook or rocker.

[RED ALERT]

i posted here a while back about my merc 260 not turning the rpm's it use to,i tryed out some of the things that was mentioned but still no success, so here's the deal: i have a 20cc bullet and had my bottom pad redone, it got water in it and the bottom started to flex and the boat would not lift, so i had the pad redone and the transom redone while the boat was apart, since I got it back it want spin the r's it did, i was turning around 8200 running around 95, now it will only turn around 6900 at 87, I can run loaded to fish with 2 people and run empty by myself and it runs the same rmps at the same speed 87, the motor runs fine, no skipping, its feels good and strong, heres the deal about the motor, the top cylinders are clean as a whistle, middle half & half and bottoms mostly black, I thought it was a motor issue so I : changed out injectors, coals, switch boxes, tryied out another ecu, spark plugs, tryied a prop 2 pitchs smaller,checked the firing, compressions real good, made sure vacum hoses,checked filters, i've done came this far so i'm willing to try anything else,THANKS

Are you sure you have the propshaft height back to where it was previous to the repair?

[mirage243]

I've seen guys add a ton of weight to a boat when they were repairing one. Sometimes a repair can weigh three or four times what the origional did.

[20cc]

not checked leak down yet, motor has less than 100 hrs on it and i aint sure about the weight but would that explain the cylinders being clean and running same rpm's and speed loaded or empty? how much weight coulld cause an issue?

[patchesII]

It did the same thing after you swapped to good set of injectors and a known good ecu? Are you sure the injectors you tried were good. Any evidence of water intrusion in the motor
I know it sounds too easy but have you checked for full throttle? That got me one time:D

[20cc]

I had the prop shaft at 5/8 above pad when the boat wouldnt lift and now I have it at 1 1/4 above pad, i checked the pad for straightness and its pretty much flat 2 to 3 foot from back, i didnt realize u could add that kind of weight from a repair since the old being wet which added weight but then again i ain't no expert when it comes to boats and motors

[20cc]

I swapped injectors and ecu from a buddys motor that runs good on his and I replaced the head gaskets and didnt see any issue with water intrudtion, I also checked the horn flap for full throttle

[patchesII]

Have you checked the fuel pressure or tried a different regulator. You could be making too much fuel pressure

[racerx]

Back the boat in the ramp on the trailer,put a real small prop on it,and wind it up,see if it revs up..

[20cc]

i have checked fuel pressure but not while running but i havent changed out regulators yet but going to

[patchesII]

Too much fuel pressure will hurt top end rpm. I'd pull the regulator from your buddies boat and try it

[Skittles]

I doubt you added enough weight to cause this especially when you said it runs the same with or without a passenger/loaded.....that raises a flag for me. It sounds like the top two pistons are fuel washed (very rich) unless its cleaned by water which I doubt considering the 2 clean pistons are on opposite sides of the motor. I would start w/ the basics here...Is compression good? Next, I would definately be cking fuel psi when running at speed as well as timing..I would also connect a timing light to all cylinders while running and make sure they all appear to be firing steady.......Id also ck the air temp sensor just a few places to start. Let us know what u find.:cool: