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Old 10-16-2011, 03:26 PM   #1
Lt. JG
 
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Default Need some help ! can't get my boat to go on plane!!

I have a 3300 se twin engine 5ltr 260 hp merc Bravo 3 units
when I cruise at slow speed Up to 1800 rpm on the engine all seems fine!
When I increase speed to go on Plane ( faster) the port engine will not go faster than 1800 to 2000 rpms,
the starboard seems to be fine
observations
1. the wake turbalance is extreme as compared to when it is working correctly
2. my helm system whem the boat was working correctly would be parallel to each other when increasing speed, Now the port helm needs to be pushed forward more than the starbard helm.
here is what was done so far
A. engines were tested by a certified Merc Mechanic, he says motors are fine
B. checked or changed all fuel line filters.
C. Mechanic indicated that the boat may have barnicales on bottomor on drive units
( Pulled boat to see if that was the case, bottom was clean !!
d. boat is out of water now,
E. yesterday I ran engines up to tempature using fresh water attached to drive unit, this is my observations
1. starboard system appears to run smooth took engines up to 1500 rpm appeared fine
2. ran Port side and noticeda wiggle on drive system, compared the props from the 2 sides and can really see any difference???
How can I test props for balance and this slight wiggle can it cause the boat not to go on plane???

any other ideas or suggestions!!!

John
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Old 10-16-2011, 04:27 PM   #2
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john
a couple of things that you didn't mention ...1)are there 2 tanks on the boat...if so...did you check the antisyphon valve....you checked the fuel system and filter....then if the engine checks out...and you still can't get rpm...then there has to be something holding the engine back..ie vacuum leak....clogged fuel filter....crappy hull....etc....if your timing is advancing properly...you don't have bad gas....then there can only be one answer....clogged antisyphon valve....so..check that out and report back..

the wiggling prop and drive has me worried...get that checked out...it means that either the propeller shaft or the prop blades have been hit hard enough to do damage and although it may work...it shouldn't cause you to hit max rpm of 2000....have the drive pulled and inspected....repair props....

hope it helps and let us know how it goes..

SP
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Old 10-16-2011, 07:58 PM   #3
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I would run the engine in neutral over 2k RPM, in the water or out, its not going to kill them for a few seconds. if it pops over 2k on the tac, its not the engine.

did you have a party of people sitting in the back? this means your plowing water, and your prop is under high torch.

Is there 1/4 full in the gas tank, this will make the boat plow w/o the 800 lbs of fuel weight down the keel.

Did you use your trim tabs or do they looks like this?



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Old 10-16-2011, 08:03 PM   #4
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Default Need some help!

Thanks for your response, The 3300 has only one tank for both engines 189 gallons
Do you think a little wiggle can cause the engine not to acerlerate after a certain speed, are there any electric interlocks that will stop the boat from going faster!!

any other ideas will be usful to me in my troubleshooting efforts!

Iam pretty sure that the outdrive will need to be pulled, but I am trying to narrow the malfunction down soit can be repaired ASAP.

John
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Old 10-18-2011, 03:13 AM   #5
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Does each engine have its own fuel pickup from the tank? If so, I would bet on a bad anti siphon valve like Seapuppy said.
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Old 10-18-2011, 01:54 PM   #6
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A couple of thoughts (mostly recaps of what has already been said). I doubt that a dirty bottom would cause this condition in only one engine. Rather I would expect both engines to be impacted. If it is a growth related issue, then running the engine in nuetral should allow the engine to go above 2K RPM's. Drag from growth would not impact the performance while in neutral. However, you already stated that you've pulled and inspected the bottom and running gear and they are clean. As stated earlier, put the drives back on a hose and crank the RPM's up well past 2K. It should be fine. Heck My merc mechanic had me run the motor while on land in gear up to 2K while inspecting the drive. It was ony for a few seconds. He's a certified merc, Yamaha, yadda yadda yadda and asured me it would be fine. I wouldn't suggest this on your own though.

Try swapping the port and starboard pickups and see if the problem follows the pickup from one engine to the other. This will tell you whether it's the pick-up or line by only swapping the hoses to the opposite fittings. If it follows the pickup, then it's the pickup or line. If it doesn't, then it's with teh motor itself. Check where the throttle cable connects to the motor. Can you manually bypass the cable and actuate the throttle directly. Maybe there's undue amounts of slop or a loose or disconnected cable. Just some thoughts.
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