- 98 Merc 150 Runs fine on land / not in water VIDEO ATTACHED

[Ant-Knee]

Hello All,

I just got my baby back together from rebuilding the carbs.. I can get her running fine on land, But yesterday I took it for my first ride and once in the water it ran real crappy, Could not get the RPMS over 1000 would stumble and die like it wasnt getting fuel.. I was trying to do the final carb(s) adjusting but it just kept stumbling and would die when trying to give it gas.

I attached a video of the motor running on the land and it sounds great to me..

How does it sound to you?
Should the fuel filter be full of fuel at all times? I am wondering if the fuel pump is bad..

Any suggestions?

Thanks Ant...

 

[79Merc80]

Re: - 98 Merc 150 Runs fine on land / not in water VIDEO ATTACHED

First, I would turn up the water pressure on the hose. You weren't getting much out of the prop while running and almost none from the tale tell. Others will chime in on the rest.

HTH, Craig

 

[NorthportTroller]

Re: - 98 Merc 150 Runs fine on land / not in water VIDEO ATTACHED

Did it run like this before doing the carbs?

Also, try running the boat on the water without the cover on it and see if it makes a difference. I had a cylinder block base gasket leaking exhaust fumes into the housing that would kill the motor if the cover was on but when the cover was off it ran fine.

 

[Ant-Knee]

Re: - 98 Merc 150 Runs fine on land / not in water VIDEO ATTACHED

Was trying to do the carb adjustments, The cowl was off..

The motor did not run before carbs were rebuilt.. It runs great now, But
as soon as I put it in the water in neutral or forward it stumbles real bad and dies, Couldnt get the RPMs over 900 - 1000 and it would just die..
On land I can get the RPMs to 3000 with no problem at all...
I am gonna take it back to the water tomorrow if weather is ok, I will get video of it on the water..
Maybe that will help..

Thanks..

 

[CharlieB]

Re: - 98 Merc 150 Runs fine on land / not in water VIDEO ATTACHED

Big difference in fuel requirements between 'on the hose' and 'on the water'.

Exhaust back pressure once on the water greatly increases the motors fuel requirements. A faulty fuel pump, leaky hoses, can cause problems that may not show while on the hose.

Disconnect the fuel hose to the carbs, point it into a suitable container, pull the lanyard to kill the ignition, crank the motor and observe the fuel stream. You should see a strong pulsed flow the diameter of the hose and spurting out at least and inch and a half.

Temporarily replace that hose with a clear hose, reconnect it and start the motor. Now observe the clear hose with the motor running and watch for any air bubbles passing thru, indicating air sucking into the fuel system from leak(s) anywhere before the pump.

Replace the temporary clear hose when finished, it is NOT rated, nor safe for continued operation.

Idle fuel adjustment must be finalized on the water and in Forward gear. Too lean and the motor will not take throttle, it will bog, lean miss, cough, and die. Adjust idle mixture to 'Best' idle speed IN Forward gear, plus almost 1/8 more fuel (CCW) to provide the additional fuel necessary for crisp acceleration. Again, too lean will cause a hesitation, bog, lean miss, indicating a need for even more idle fuel mixture. Make very small adjustments from here, only the width of the screwdriverblade slot. Repeat holeshot testing until perfection.

 

[CharlieB]

Re: - 98 Merc 150 Runs fine on land / not in water VIDEO ATTACHED

Since the carbs have been off, have you check the carb link and timing synch?

Does this motor have an 'idle stabilizer module'? If so, remove it and toss it into the trash. Adjust WOT timing to 22 degrees while cranking with the spark plugs removed and all spark plug wires grounded.

 

[Ant-Knee]

Re: - 98 Merc 150 Runs fine on land / not in water VIDEO ATTACHED

Big difference in fuel requirements between 'on the hose' and 'on the water'.

Exhaust back pressure once on the water greatly increases the motors fuel requirements. A faulty fuel pump, leaky hoses, can cause problems that may not show while on the hose.

Disconnect the fuel hose to the carbs, point it into a suitable container, pull the lanyard to kill the ignition, crank the motor and observe the fuel stream. You should see a strong pulsed flow the diameter of the hose and spurting out at least and inch and a half.

Temporarily replace that hose with a clear hose, reconnect it and start the motor. Now observe the clear hose with the motor running and watch for any air bubbles passing thru, indicating air sucking into the fuel system from leak(s) anywhere before the pump.

Replace the temporary clear hose when finished, it is NOT rated, nor safe for continued operation.

Idle fuel adjustment must be finalized on the water and in Forward gear. Too lean and the motor will not take throttle, it will bog, lean miss, cough, and die. Adjust idle mixture to 'Best' idle speed IN Forward gear, plus almost 1/8 more fuel (CCW) to provide the additional fuel necessary for crisp acceleration. Again, too lean will cause a hesitation, bog, lean miss, indicating a need for even more idle fuel mixture. Make very small adjustments from here, only the width of the screwdriverblade slot. Repeat holeshot testing until perfection.

Hello Charlie,

I was trying to complete the adjustments yesterday after I read your post.. When on the water it definetly bogs and dies as if it starving for fuel, I tried to adjust the carbs in gear with 1/8 increasements at a time but it got to the point the idle screws were gonna fall out.. So I started over from the beginning but the same thing happened did this 4 or 5 times,

I have an extra fuel pump here, maybe I should just swap pumps and see if it changes.., First I will disconnect the fuel line and see if it spurts out like you say.. If not I will swap fuel pumps and see what happens.. If I take it to the water I will get video of what is going on..

Thanks.

 

[Ant-Knee]

Re: - 98 Merc 150 Runs fine on land / not in water VIDEO ATTACHED

Since the carbs have been off, have you check the carb link and timing synch?

Does this motor have an 'idle stabilizer module'? If so, remove it and toss it into the trash. Adjust WOT timing to 22 degrees while cranking with the spark plugs removed and all spark plug wires grounded.

Not realy sure on how to do this..

 

[Ant-Knee]

Re: - 98 Merc 150 Runs fine on land / not in water VIDEO ATTACHED

Hello All, Just a quick update, Turms out I had a bad coil.. Will have one today and hopefully will be good to go.. Thanks Ant...