1989 225 Yamaha excel Runs great Except at WOT

[Mueller1956]

Here's the story, 1989 Proline 230 with a 225 Yamaha excel engine. Complete rebuild 24 months ago by one the areas best Yamaha Tech: Ran fantastic until I let it set for a couple of months. (About this time last year) Operational characteristics: Starts great even after a long period of no operation. Idles fine, but as you put the throttle down instead of a neck snapping hole shot (which it used to do) I have to look over the starboard rail to make sure I am not running over anyone. The bow stands straight up and it takes 45 to 60 seconds for the boat to plane out. RPMS at WOT are 4200. Previous 5300 to 5500. Speed has decrease also of course, 32mph now instead of 42. Runs smooth with no hesitation at all........... What I have done so far: Carbs have been gone through and cleaned. Plugs and wires, caps too. Coils on number 2 and 4 were close to out of range so they were replaced. Knock sensor, crank position and throttle position sensor check out OK. Fuel pumps and filters changed. Empeller and housing changed. Lower unit not binding. And the boat is not full of water in the hold. Although it feels like it has 20 people on board. Any assitance will be greatly appreciated:

 

[Ray Neudecker]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Are you running premium fuel? Those motors require 91 octane to keep the knock sensor from retarding the timing to -7 degrees.

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Here's the story, 1989 Proline 230 with a 225 Yamaha excel engine. Complete rebuild 24 months ago by one the areas best Yamaha Tech: Ran fantastic until I let it set for a couple of months. (About this time last year) Operational characteristics: Starts great even after a long period of no operation. Idles fine, but as you put the throttle down instead of a neck snapping hole shot (which it used to do) I have to look over the starboard rail to make sure I am not running over anyone. The bow stands straight up and it takes 45 to 60 seconds for the boat to plane out. RPMS at WOT are 4200. Previous 5300 to 5500. Speed has decrease also of course, 32mph now instead of 42. Runs smooth with no hesitation at all........... What I have done so far: Carbs have been gone through and cleaned. Plugs and wires, caps too. Coils on number 2 and 4 were close to out of range so they were replaced. Knock sensor, crank position and throttle position sensor check out OK. Fuel pumps and filters changed. Empeller and housing changed. Lower unit not binding. And the boat is not full of water in the hold. Although it feels like it has 20 people on board. Any assitance will be greatly appreciated:

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Are you running premium fuel? Those motors require 91 octane to keep the knock sensor from retarding the timing to -7 degrees.

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Are you running premium fuel? Those motors require 91 octane to keep the knock sensor from retarding the timing to -7 degrees.

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Thanks Ray for your response, I have always ran the highest octane fuel. But it has set up for a long time. Although I have used Stabilizer I wonder if the gas can get contaminated? This weekend I put 20 gals on top of the 40 plus gals and ran it with the same results.
Mike

 

[Ray Neudecker]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Even with stabiliser, the results of octane loss from evaporation of the additives now used to provide the octane has been very noticable. I have seen a lot of detonated pistons caused by the fuel.
The old methods of dealing with this have basically been negated by the newer losses due to the rapid evaporation of the additives.
Testing with a timing light under load is the best way to determine what is happening.

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Thanks Ray will strap myself in for timing underway.
(Closed Transom with a Gill Bracket!)

Thanks again

Mike

 

[Ray Neudecker]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Might be a lot safer and easier with it strapped to the trailer and a test prop preferably. It will show up almost instantly after hitting the throttle.
The only real solution is to drain the fuel and put in something else and trying with fresh fuel. This test will allow you to justify doing so.
I have older vehicles to transfer questionable fuel to and burn without a problem.
Good luck and keep us informed.

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Ray,

Drained the fuel and replaced it.

Checked the timing uderway and saw that it was advancing.

Are things pointing to the Carbs?

Thanks

Mike

 

[Ray Neudecker]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Yes they are pointing to a fuel restriction, Bypass the engine mounted filter and fuel disconnect as well as replace the fuel pumps to eliminate them. Later models had a different filter that wasn't as likely to cause a problem and eliminated the fuel disconnect . Also replace or eliminate the anti siphon valve at the tank and be sure you have a fresh water seperator filter.

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Will do.

Thanks

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Replaced all related Fuel connections, pumps and filter. Operation was slightly better. Now she's up to 4300 rpms. I have noticed that the port plugs seem to be fouling up with carbon after 2.5hrs of operation.

Checked the compression and each cylinder is 155 to 120. Pulled the Carbs and cleaned them out again. Minor black fibers were in the main jets that looked to be old fuel line fibers. (Replaced fuel line)

Tried my alternate prop with the same results.

Verified that the timing was advancing under operation.

I feel like I need a priest for an exorcism!

I belive that the CDI was relaced. I will check the invoice.

Stator? Can a Computer give out on one or two cylinders?

Thanks

 

[kavika]

Re: 1989 225 Yamaha excel Runs great Except at WOT

I had a similar problem.

They did a vacume test on the fuel system. Had restructed fuel line, which when replaced everything ran fine.

 

[Ray Neudecker]

Re: 1989 225 Yamaha excel Runs great Except at WOT

You are most likely still dealing with a fuel restriction. The black vibers are often the bowl gaskets coming apart inside the carbs.

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

I only have one fuel line to replace. The one from the bulb to the engine.

I think what I am having trouble with is that top two cylinders (2&4) are the ones that seem to have the abnormal carbon build up. Which I thought could mean a weak spark.

I will continue forward with fuel restriction.

Thanks for the input.

Mike

 

[CaribbeanSoul]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Mike---are you still have the fuel problem?? I lived in Tampa for many years and had the same problem happening to my Pro-Line. What we found was the anti-syphion valve in the fuel tank was corroded and the ball inside was sticking, restricting the fuel flow----just a thought

Steve

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Thanks Steve,

The boat has had the tank replaced and now had a straight 90 on it.

I finished replacing all of the lines the bulb primer and the oil lines.

(Also found a broken wire from the engine a yellow/red. repaired)

Put it in the water a week ago and ran it hard for 2 hours. Still has the low top RPM and bad hole shot.
(I am beginning to imagine things! Thought that is sounded diferent when it first started.)

So after the run I pulled the plugs.........

Number 2 and four top two plugs on the port side were so full of carbon that the gap was bridged! All of the other four plugs were in great shape. In fact a lot better than they had been........................

What do number 2 and 4 have in common that could cause such a build up of carbon? Could the trigger coil be the cause? I thought that the trigger coil would be bad on 1 and 2 if so not 2 and 4? Then I thought that may be half of the coil could be shot on 2 of the coils. Compression test shows 155 to 120 on all cylinders..............Could a head gasket cause.......Too much oil in only 2 and 4?

The search continues................................Closer but not fixed......
Thanks to all that have read the saga and have had simular situations......

 

[JUSTINTIME]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Compression test shows 155 to 120

that is not good

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Sorry 115 to 120.