mopower

OK , I give . I've been battling this problem all season and getting nowhere
Past two years I've been running 28 Bravos and 3000 rpms got me 50 mph. This year it gets me 40 mph and I have to stagger my sticks to get both at 3000. Something is slipping in the right engine/drive/prop. Found some rubber in bilge so I changed the coupler...no help but now clean. Threw on a spare drive...no help. Tried spare props...no help. Reversed rotation(turn in instead of out)...no help ,but did get a roostertail . Removed speedo pu...no help. Yesterday lifted boat to inspect bottom under trailer bunks and all seems ok.
At 3000 rpms my sticks are staggered almost 2 inches. If I run the right engine up to 4000 , nothing else changes (just revs more), if I run the left engine up to 4000 the boat speed increases and the right side increases also because I'm lightening the load on it.
Finally , slam the sticks to the dash and the right one is turning 5900 and the left 4800 and a top speed is off a good 10 mph.
I also checked the tachs with a third tach and they are ok and my speedo has been and still is within 1 mph (usually lower)
of my GPS.
Virtually everything has been changed or swapped or reversed twice with the exception of the engine coupler and the bilge is clean. My parts guy swears in 20 years he has NEVER seen a bad new coupler but will concede he has seen new parts bad. It has also not gotten any worse and if its been slipping for 10 hours now you woould think it would HAVE to be getting worse
I also tried 30" Bravos and the only change was 200/300 less rpms on both engines.
The poor left engine is down in rpm because its doing most of the work.
With the great minds on here are there any other ideas? I'm totally F'n lost.
Sorry for all the reading.

Dave1972

This may be somewhat remedial but have you checked the throttle linkage/cable to make sure both are adjusted properly and that WOT is actually WOT? I was going to say it was prop related and maybe a spun hub but since you changed that...that option isn't valid either. How about fuel filter or anti-drainback valve? Fuel pump? Have you checked fuel pressure?

Hmmm...this does sound odd.

Gary Anderson

Have you checked the ignition secondary? A bad/arcing wire or cap wil cause high tach readings and loss of power.
Gary

Mr Gadgets

Thinking out loud here.. If the right engine/drive is free wheeling.. and the left has the load, what happens if you take both up to 4000k.. and then pull back on the left engine.. see if the righ one ever does carry the load.

What i am saying is, will the boat stay on plane with one engine? If it stays on plane with the left one and not the right one, then bad water to the prop? Can you turn the wheel and see a difference in load to right or left?

If you had a drive line slipping problem, it would seem to break loose and free rev at some point. I cant see a couple holding on "sort of". Can you mount your wife or gf on the swim platform and have her look at the water getting to each prop?

Like I said, just thinking out loud. You have tried adding load to the left motor. Try subtracting it and see if the right one ever ponies up to holding any load at all..

With all you swapped, it seems not be a hardware issue.. I am thinking water to the prop issue..

Good luck.. this boating thing is suppse to be fun, not perplexing..

Dick

shawn

Could that engine be down on power due to weak/broken springs or something else going away?
Shawn

mopower

Dave , throttles are both wide open when sticks are.
Gary, new caps and rotors.
Mr gadgets, My thought too. Thats why I removed the speedo pu and inspected the bottom of the boat. Also why I tried turning the props in , hoping they would pu water differently.
When I slow the left engine down , the boat slows and the right engine slows. Don't know if it will stay on plane or not. I havn't tried that.
Shawn, that was my original thought back in May but I realized when I put my GPS back in the boat the speed was down. For 2 years 3000 got me 50mph now 40. Same speedo same GPS.
The slower engine will push the boat faster when throttle is advanced the right one will not , just the rpms increase.

Good work guys...keep the questions coming

Wally

Have you done a compression test on the engines??? may give you some clues about the engines health.....also try hooking up a vacume gauge to both engines to see what they are doing when under load......

Inspect the prop hubs as well.....

mopower

Engines pump 180 across the board. Changed to 30" Bravos and lowered both engines 200/300 rpms.
Like I said before hit the right engine and rpms increase and nothing else. Left engine will increase boat speed.

pachangalpina

have you checked the timing and timing advance?

mopower

Yep. Also advance the throttles to 3000 in neutral and the sticks are side by side. Advance the over 3000 IN gear and the left engine moves the boat faster , right engine just revs faster(no change in speed)