98 Yamaha 150 V-max Problems.....

[brownies]

Cold weather blues....
Engine/Heads/Carbs 89 Excell.
Electronics and everything bolted to it 98 150 V-Max.
Been running fine for 9 months. Several weeks ago it began to get difficult to "keep" running when 1st started in the morning. (just figured it was cold natured and cold air and cold water).
Spun hub in 25p 6200 wot prop.
Replaced with 23p which then turned wot to 6400 rpm.
Not sure if that had anything to do with this problem since "some" of these symptoms had already begun...
1. Seems to be getting harder and harder to keep it running/idling prior to 1st launch (four mornings per week).
2. After a 5-10 mile wide open sprint, set it down and idle for a few minutes, take off again...and...it bogs and surges intermittently and will hold at lower rpm...but...slowly it will finally get all it's speed/rpm back. (may take it 5miles to get there though).
3. It will fire up and idle fine the rest of the day though.
4. Couple months now it has what seems like an intermittent miss/spit/sputter/surge? on and off at a hard idle (under a load, going just fast enough to keep it from trying to plane....or, as fast as you can push the idle speed in a no wake zone).

Fuel pump Mallory elect. Holds 6lbs at idle and while reving it in a tub of water. No drop in pressure, No pressure spikes. Regulator located on motor right at the carbs. New fuel lines. Yamalube in every tank. 30gallon tank tank clean and run about 40gal of fuel through it every week. Good water pressure.
JUST: removed, cleaned, re-adjusted and/or checked carb settings (kitted them 8 months ago). Compression 145lbs each EXCEPT the bottom two cylinders which are 130lbs each. New plugs. No linkages/controls are sticking, hanging, or getting bound up. Timing all correct.
Plugs clean, but, DARK DARK BROWN prior to changing them. AND...Few drops of moisture on one of the lower 130lb cylinders. (figured it was just condensation from setting a couple of days). Can't find any water or moisture after playing with it in a tub.
Reeds are hydtrotech and going on two years use now.
Acts to me like it's running rich or loading up for some reason. Even in a tub at part throttle it just doesn't "sound" right. Not crisp and smooth throttle response just revving it. It's more of crackling/loading up sound.

Any ideas? and....HOW to check for leakdown in a 2stroke? Rings leakdown wouldn't be a problem (just hold the piston up) and maybe that would tell me if I've got a blow headgasket into the water port, but, How to leakdown test in order to know if I've got a blown crankshaft seal or crankshaft ring?

Just where do I go from here. It doesn't bang/pop/backfire. It does surge/bog though and I think I've worked my way from the tank to the intake manifold and found nothing wrong. What next?

 

[Ray Neudecker]

Re: 98 Yamaha 150 V-max Problems.....

Are you saying you dropped the complete 89 powerhead on the later model midsection? Are you running premium fuel? Have you checked the TPS? Did you remove and block off the fuel pumps when you installed the External fuel pump? Have you examined the fibre glass reeds for leakage? Are you running a seperate water seperator filter? Have you bypassed the engine mounted filter and plumbeb the fuel line direct with no quick disconnect?

 

[brownies]

Re: 98 Yamaha 150 V-max Problems.....

Are you saying you dropped the complete 89 powerhead on the later model midsection? Are you running premium fuel? Have you checked the TPS? Did you remove and block off the fuel pumps when you installed the External fuel pump? Have you examined the fibre glass reeds for leakage? Are you running a seperate water seperator filter? Have you bypassed the engine mounted filter and plumbeb the fuel line direct with no quick disconnect?

Raysir,
Now you know better'nat....
Removed 98 150 powerhead. Installed 89 Excell powerhead. Put all of the 98 electronics back on. (No TPS sensor on a 98).
Yes, premium 93 ocatane fuel.
Fuel pump holes are blocked off/sealed.

I've not checked out the reeds yet. (kind of hoping somebody might advise me to do that, IF they thought reeds could cause these problems).

Yes, separate water filer....no water, looked good.
Went ahead and replaced the filter trying to solve this problem couple of days ago.

I have no engine mounted filter. I have no quick disconnects. All fuel line is new. Water separator/filter is new. Pump is working. 6lbs constant four inches prior to entering carbs. (7lbs not running, 6lbs idling, 6lbs revving in the tub).
Carb were kitted with new parts 8 months ago.
Just cleaned carbed again, new spark plugs. No change.

This almost seems to be cold weather related. Started having problems in cold weather. Then again, I have been running 6400 rpm since it got cold also.
Old spark plugs LOOK to be in like new condition, aside from from being COFFEE Colored (less the cream and sugar).

I did all of this changing stuff last year and it's been running great up until about a month ago (when it got cold, which, is about the same time I changed props also).

Example: I get to the lake, fire it up, let it warm up while I park my truck. Get in the boat, put it in gear and....it dies. Battle with it trying to get it started again. High idle it trying to "clear it out". Drop it back to idle...it'll die.
FINALLY, I'll get in gear and moving at a fast idle.
Launch and run GREAT for 10 miles. Come off plane, idle for 3min, Take off again and it'll surge, go, surge, go, surge, go. Slowling picking up rpm......5 miles later it's back to running good.
Shut it down, fish for a while. For the rest of the day it will fire right up, idle fine, BUT, it will take five miles to get to top speed if when I run again.

 

[Ray Neudecker]

Re: 98 Yamaha 150 V-max Problems.....

It was necessary to know which electronics you were using since the Excell engine had a computer, TPS and knock sensor as well as the timing pick up sensor that are not in the electrics of the 98 150 model.
Since the crank sizes are different , It requires changing the top bearing to make everything compatible on top.
The reeds could be a cause of the problem as well as a fuel restriction. Have you changed or eliminated the anti siphon valve to the fuel tank?
I have worked mostly with the BLue Holley and have not seen the drop in fuel pressure from engine on to running you are experiencing. 7 lbs is where the fuel starts leaking by the needles and seats. 5 lbs of running pressure will work fine. We normally set the pressure at 5 1/2 lbs while running on the race motors.

 

[brownies]

Re: 98 Yamaha 150 V-max Problems.....

I'll check inside the tank and drop the fuel pressure down to 5lbs.

 

[brownies]

Re: 98 Yamaha 150 V-max Problems.....

It's still today and not had a chance to do the above yet. Still racking my brain though....
Acts sort of like it like before I "kitted" the carbs 8months ago. But, I did remove, clean, and double checked the settings. Just seems hard for me to beleive that a carb that gets 10 gallons of fresh fuel run through it every other day would need "kit parts" again 8 months later.

And, I wonder how long those hydro-tech reeds are suppossed to last before they start breaking down. Or, do they ever break down? Seems they might be something that could "wear out" with lots of use.

 

[Ray Neudecker]

Re: 98 Yamaha 150 V-max Problems.....

The problems with fibreglass reeds are common. They range from tattering to blown. One of the more common problems is that they just no longer seal properly.
We change the race motor ones yearly.The fishing motors vary tremendously in there wear. Some run for years with no known problems and others don't last long. Brand doesn't seem to matter.

 

[brownies]

Re: 98 Yamaha 150 V-max Problems.....

BTW, does Yamaha make a replacement bushing for the throttle linkage that makes contact with the timing cam? It'd be a bushing for an Excell.
That flat spot on that bushing bugs me.