1990 Yamaha 150 no power under load...help....

[Bahlockay]

i'm having issues with the motor bogging under load will get up on plane but very slowly and rpm tops at 4500ish also has vibration while getting on plane.
motor is on a 89 champion 17foot motor 150etld

how the issue came about?
i was rolling through the river cruising. seen some people fishing on side the bank came off plane like normal shut the motor off chit chatted with them and cranked it right back up and the when i tried to get on plane it took near 20 seconds for the bow to come back down... went in and out a handful of times "full power-no power" and that was a wrap done know what happened..

here are things i've done and or checked

• compression 110--112 all the way around
• cleaned carbs jets etc
• cleaned/checked fuel pumps
• checked fuel filter
• drain fuel lines and carbs and ran fuel line to new gas in a 5 gallon jug
• new spark plugs
• new ends on ALL fuel line fittings "clamps etcetc"

i also pulled the coil packs while engine was running some made a difference and some did not at 1300 rpm in the driveway
i tested spark on the coil packs and they will shoot a spark strong enough to stretch about 4 inches or so and the coils that seemed to have no effect DO indeed work...
also tested spark plugs to make sure they had visible sparks as well...
i have compression spark and fuel but yet no power under load.
also in the drive way i can rev it up no problem idles fine and idles fine in the water and revs just fine in the water
put in gear =slow I typically run around 53ish mph top speed now is 43-45

at this point im at wits end and seeking help even after reading the 266page yammy service manual...

[21XDC]

Cleaned/checked fuel pumps?....... Not replaced?

[bassboat1]

Check the piston tops for signs of water intrusion? If you're got compression and spark, it has to be fuel.

[PSM207]

Also check primer bulb. I've seen the parts inside these bulbs break and restrict fuel flow.

[Amistad Tackle]

Likely a fuel restriction or your lift pumps.

[Bahlockay]

no restrictions on fuel pumps trust me on that
one no water on top of pistons or cylinders
primer bulb is in top notch shape check valve also works on primer bulb

[Amistad Tackle]

Are your lift pumps leaking? Loosen and pump the bulb. Any fuel leaks then replace.

Could be one way check valve at the tank. I've had that cause issues.

With Yamaha almost always fuel related.

[Bahlockay]

Still working on the issue once I find fix I will update!

[n_gong]

How is the timing and linkage movement ?

[Texas Rig]

It sounds like a fuel problem similar to the issue I had with my 1990 ProV. I had to use the process of elimination to find the problem. First, I purchased a small 3 gallon portable tank and connected it to the fuel line at the inlet to the primer bulb. Get a buddy and take the boat to the lake. Remove motor cawl and carb intake box to expose the throats of the carbs. Do a couple of hole shots to see if there is any difference. If things are better, the fuel issue resides in the boat side of the fuel system and not the motor. If things didn't change, have your buddy rapidly squeeze the primer bulb while at top rpms. If you feel a difference, it's most likely the fuel pumps. If no change, have your buddy squirt a small stream of gas in to each carb throat while your at WOT and on plane. If you feel an instant surge and gain in power, take note of which cylinder it is as you have a restricted main jet. If things didn't change with squirting gas, start looking for vacuum leaks on the carbs. Hint, the silver metal plate on top of the carbs are prone to leak if not tightend properly. Good luck!

[Bahlockay]

more testing will be done this weekend. the heads are off the motor at the moment and are getting put back on this weekend along with some new parts will keep posted and at the end i'll do a full write up!

[YoungGun29]

I just went through this, have you checked your plugs for water? I tried everything, ended up being my inner exhaust plate gasket.

[Bahlockay]

Put heads back on changed computer pulled fly wheel visually checked pulse coil and stator top cylinders 1&2 do nothing when coils are pulled when running. I can get #1 to have change when #3 is also in plugged. #2 does nothing at all I’m thinking could be reed’s possibly. Pulled carb 1&2 and swapped them problem stayed at 1&2 cylinders which would rule out a carb issue. Thoughts?

[Bahlockay]

Just another update I cleaned the motor and I mean it’s spotless looks like it’s brand new and after about 2 days I open the cover and find fuel in the cowling and leaking out the carbs. I ordered 3 used carbs (my carbs seem to have some funky things on the inside from previous owners) and a rebuild kit. Will post back once that’s changed. I think it’s leaking out the carbs now that I put a check valve on the fuel tank to keep it from leaking down.

[Bahlockay]

Ok guys the boat is now fixed! I’ll do a full write up here shortly still working out idle screws with the new carbs. Long story short for now

[Amistad Tackle]

Good to hear. Interested in what the issue was.

[Bahlockay]

You and me both I’ve tested both top carbs… the used set off eBay and my used carbs. The top carb was the one causing the issue. Both eBay set of carbs and my carbs seem to have no difference that I’ve seen so far. Both had rebuilt kits on them and both of them the floats float in fuel….. I have absolutely no idea why my old carbs still don’t work but the used set on eBay did…