Excel 225 "bogging down"

[jamaso]

I have been told that the '89 model 225hp Excel I have, has a computerised system that retards ignition on initial heavy accceleration. This means that it is no good for skiing. I have tried all options with prop sizes, various positions on trim and jacking plate etc. with no success. Could someone please confirm that this is the case as I have only heard it from one mechanic. Also if poss. any details that might help. Thank you

[Hamfisted]

Never heard that before. What I have seen is the O-ring seals on the main jets deteriorate or crack and allow engine flooding when trying to accelerate to plane the boat. I would pull the main jets and inspect them. If you see any crack or deterioration of the orange O-ring seals at the end of each jet replace the O-ring. Here in the states they're about $4 a pop at the dealer but you may have some other supplier down there. They are synthetic material O-rings that withstand fuel. Regular black rubber O-rings will not work. How are the fuel pumps? Can you pump up the primer bulb firm? If not the fuel pumps need to be inspected for diaphragm leaks. Good luck.


Mike....... Miami, FL

[boats.net]

Actually I think that engine is an excellent ski engine it has quick response on take off. It has a knock sensor that if detects a knock in engine will retard timming if knock doesn't go away it will retard timming again it will keep on until knock goes away, you normally notice it on top end the engine will slow down a couple hundred RPM's.Check compression and compare cylinder 1 to cyl. 2, cyl. 3 to 4, 5 to 6 they should be within 10 percent of each other, if low then run a treatment of Sea Foam or Comustion Chamber Cleaner through engine to even up compression. That engine also has a throttle position sensor that needs to be checked.

[jb123]

bogging on takeoff sounds like your motor is starvin for fuel, then catching up slowly.i`d check from fuel pickup tube to carbs. does it run fine at all other speeds?

[jamaso]

Goes like a shot cat once on the plane.

[Ken]

jamaso,
If your outboard was allowed to set up for more than three months w/o being run, and was not properly "winterized" before storage, then you very well could have clogged-up carbs.
I would do a shock treatment with SeaFoam or RingFree - if that did not help, then I would tear the carbs down, clean, and install a carb kit. Be sure to check the o-rings at the end of the high speed jets like Hamfisted said.
Also, your problem could be bad spark plugs - if they have not been changed in the last year, do it.
Good luck [img]smile.gif[/img] ,
Ken K

[jamaso]

Thanks for your advice. Carbys have now been stripped down, floats adjusted and all completely serviced! No noticeable difference. Mechanic now indicating that the motor is breaking down under load. Based on timing check results we could be up for a replacement micro-computer apparently. A$2300 from Japan just for a start as none available in Oz. Any thoughts?

[Hamfisted]

Its tough to troubleshoot without actually seeing the motor. But these guys here at Boats.net have the CDI unit for about $445 p/n 6G5-85540-12-00 if that's what you're refering to. Do you have a service manual for your motor? It outlines the procedures for setting the timing. Or is your mechanic just using a standard timing light?


Mike

[jamaso]

Pardon my limited knowledge. I have been given the run-around by many local "experts" here and have become more and more confused. I believe the mech. I am dealing with now is on the right track though. My understanding is the CDI unit is a different part to the computer. The critical thing seems to be the control of the timing advance. I believe he is planning to use a timing light & does have manual. He has gone away for the Xmas break & I cant see us getting to it until the New Year, so will keep you posted. Will definitely look at the options if any for spare parts. Safe & Merry Christmas to all!

[Ken]

jamaso,
Let's review - starts ok, idle ok, low speed ok, high speed great, but mid-range bogs down - carb overhaul and does same thing - I would eliminate fuel problem. Sounding more and more like ignition advance control. Tell your mechanic to follow the procedure in the Yamaha shop manual to check the ignition advance. I believe the ignition advance is purely mechanical - sounds like it is hanging/sticking on something.
I checked the parts diagram (above) for your motor - could not find a separate "computer" - I believe you only have a CDI - and I can't imagine the CDI working at low and high speed, but not mid-range .
(Oops, I stand corrected) - there is another electronic module called the "control unit assy" - this must be the "knock-sensor" module. It would be logical that the knock sensor control could be faulty and telling the CDI to retard the spark too much during heavy acelleration. Hopefully, the Yamaha shop manual has a way to test this little rascal, because Yamaha is sure proud of it $$$$$.
Good luck and Merry Christmas [img]smile.gif[/img] ,
Ken K

[jb123]

(I have been told that the '89 model 225hp Excel I have, has a computerised system that retards ignition on initial heavy accceleration.)

How does it respond upon light acceleration?
If is runs fine at the top end I still think your chasing the wrong culprit.9 of 10 times your issue will be fuel supply,especially on the older carburated models.Ask your tech if he will refund the $$ if the cdi does not repair the issue. Either way,let us know your outcome.

[jamaso]

Thanks for your replies. The initial acceleration from standing start is where the problem lies. I can travel 20 metres with the motor labouring before it gets out of the hole even without a skier. Will check as you suggest & review the fuel supply option. If it is the CDI it looks like I may be able to find one a little cheaper than the dealers quote!

[jamaso]

[boats.net]

Just a couple of notes about that engine. That is one of two Yamaha engines that uses 89 octane gasoline,the Excell and F250 will not run well on regular gas. The Excell needs to be prop to around 6000 rpm's you can prop it just below the rev limiter 62-6300 rpm's. The timming is con*****ed by the computer(no adjustments can be made on timming)but the computer changes timming base on signals from knock sensor, crank sensor, throttle position sensor,thermosensor and pulsor coils. So if timming is out of specs or erratic then test all sensor's before changing out computer.