2005 90hp 2 stroke bogs at WOT

[kne6768]

I'm new to outboards and this forum, but need some helps trying to diagnose an issue. Bought this motor recently and can't figure it out. It starts fine, idles good, runs smooth and even up to about 3k rpm, then begins to lunge or bog down. It goes lunges up and down about a 1k rpm or so. Never dies, just bogs and lunges.

I've replaced the fuel lines, bulb, filter, cleaned the 4 carbs. Still it persists the same. Maybe even a little worse.

any ideas or suggestions would be greatly appreciated.

Kevin

[Solarman]

Kevin check the shift sensor, if bad it limits motor to 3k RPMs.

Good luck.

[kne6768]

Thanks for the reply. Checked my Sealoc manual for location and it says those are only on the V6 motors. Where would it be located on the V4 90HP?

[Solarman]

Look around the shift linkage for a switch that only operates from the shift linkage. It is only activated by shifting from forward, neutral, and reverse.
Ilk see if I can find it in the parts listing.

Let me know if you find it.

[Solarman]

Wasn't able to find it in parts either. Most motors have the sensor, yours being an 05, thought it would. Then it may still have one. I couldn't find a breakdown on the controls for your motor, it could be located there?

will keep looking.

[kne6768]

Thanks for the suggestion. I am continueing to search for the issue.

When the motor begins to lunge, if i pump the bulb, it will run apparently fine. I'm leaning towards the fuel diaphragm in the vro mixer pump. I think it is pumping oil in quantity relative to the throttle and not enough fuel volume based on the throttle or the amount of oil being pumped into the carbs.

I'm also looking into the temp sensors being the problem. Some say they can throw the motor into "SLOW" mode. I hope to get to try a few things today or tomorrow, weather permitting.

I want to try everything simple before buying a new vro pump!!

Thanks again.

[jvd61182]

I'm having the exact same problem with my 48 hp johnson and I've been told if you prime the bulb while the problem occurs and that makes it better its a fuel issue. I tried that with mine to no avail so good luck and I hope you find the real cause because I would sure like to know what it is. I've replaced just about everything fuel related! I'm waiting for the manual to come in but could someone tell me if I have a shift sensor???

[Solarman]

Jvd, if you have a shift sensor it would most likely be mounted on shift linkage at motor. Many motors had them to prevent over revving in neutral. I'm not sure if you have one?

Good luck.

[Solarman]

Kevin, if motor runs ok if priming bulb, then a fuel issue most probably. Fuel pump it's a good call. Two other possibilities. One; is any air getting in fuel line before primer bulb? Two; is there a chance there is a restriction in fuel flow at the float needle valves (trash on backside of needle valve seat-small piece of debris could affect full fuel flow, and often it is overlooked/ not removed when cleaning.), or, possibly the float settings are slightly low, allowing float bowls to run low on fuel at higher RPMs?

Good luck, post back if find anything.

[kne6768]

I cleaned the carbs and throttle plates. No change.

I checked every switch and sensor i could locate and test. No change.

I rebuilt the fuel side of the VRO pump and it now runs smooth at about 4600 rpms. The diaphragm on the fuel side turned out to be the problem. I can't say what the previous owner used for fuel or their maintenance situation. It's such an easy fix, i'll carry a rebuild kit on the boat with me.

Thanks for all your suggestions and recommendation.