Motor bogs down under load......most of the time

[Roland817]

Hello all, brand new to the forum and in need of some help. I have a 1995 175 hp Johnson ocean runner. It was running great until About two months ago when I bought some bad fuel and almost got stranded offshore. Lots of water in the fuel and I had to keep dumping the filter to make it back to harbor. Once I got home I went ahead and pulled the fuel tank and cleaned it out completely and replaced fuel filter/water separator and reinstalled. I also rebuilt all 6 carbs at this time with new bowls and floats. I refilled with clean fuel (pre mix 50:1, vro is disconnected) and dropped boat back in the water. I adjusted fuel/air mixture screws to get engine idling right. Engine fires right up and idles perfectly. The problem is when I go to throttle the motor up with a load it typically bogs down and if I don’t pull off the throttle the motor will die. Sometimes it takes right off and runs just as it should until I throttle it down and when I try to throttle it back up again it will bog down and die. I’ve tried running it off my 6 gallon jon boat tank and it does the same thing. I replaced the fuel pump thinking maybe it was weak but no change. I’ve checked compression and it is all good as well. Any ideas? Thanks in advance.

 

[joereeves]

Having the engine hesitate and/or die out when throttle is applied is usually due to:

A sticking timer base under the flywheel.

Partially fouled high speed carburetor jets.

Linkages out of adjustment resulting in the throttle butterflies opening too soon in relation to the timing. The butterflies should just start to open when the scribe mark on the cam is dead center with the throttle roller.... assuming that the distance between the vertical throttle arm and the cam has not been tinkered with <--- If this linkage distance has been changed, the idle timing will need to be reset with a timing light.
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Although this will not cause a bogging problem... Also check the diameter of the roller. It should be approximately 3/8" in diameter... if it is only about 1/8" in diameter, replace it. The roller from day one was always a one piece roller that lasted forever. Some idiot redesigned it to be a two piece roller... 1/8" of hard black material with a clear covering to make up the 3/8" diameter... BUT... the clear covering breaks away in time that changes the idle timing and makes it impossible to obtain full throttle.... brilliant engineering!

 

[faztbullet]

1) If it has adjust screws this makes it a 60° motor. Boat must be untied, in gear, at temp and trimmed level to adjust mixture.
2) Motor doesnt have a timer base but a optical eye on top of flywheel.. never seen one stick
3) Timing should only be set with timing tool as timing light flashes can confuse eye
4) The linkages can slip on these models and cause bogging and the roller cover as posted...

The roller(yellow looking part on carb linkage)

linkage slipped and roller not touchng

Loosen screw, move roller as indicated by arrows.

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Correct roller position.



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[Roland817]

Thank y’all so much for taking the time to respond. Yes sir, it is a 60* motor. The roller in the first picture that faztbullet posted is pretty new and in good condition. The roller from the other pics seems to be in the correct position as well. However, when I adjusted the idle screws the engine was in neutral and tied to the dock. I will try to readjust these with the boat in gear and see if that changes anything. Could a timing light be used to at least check the timing just to see if it is out?

 

[Roland817]

So I adjusted the idle screws again while boat was in gear and trimmed level and I’m still getting the same issue. I also checked the timing with a timing light and it seemed spot on. One thing I found is that when I throttle up I can get the boat to plane out if I push in key which I believe either chokes the motor or primes the carbs. If I continue to do this periodically the boat will stay running. I’m at a loss. Boat was running great before I rebuilt the carbs so I know it’s something I did or didnt do. Any ideas?

 

[joereeves]

Pushing the key in activates the fuel primer solenoid, causing fuel to bypass the carburetors with a direct route to the intake manifold...... and you state that this act (in effect) temporarily cures the problem.

This indicates that fuel is NOT flowing thru the carburetors properly. Best to double check your carburetor work. Be sure to clean the high speed jets thoroughly, carefully with a piece of single strand steel wire if needed.

 

[Roland817]

ISSUE RESOLVED!!!! So I rebuilt the carbs again and did a link and sync and motor was running alot better. Boat would jump up on plane and run great for about ten seconds at which point it would bog down and die. Boat would run great at lower speeds for extended periods of time so I figured it had to be a fuel issue. I traced the line back to the anti siphon valve on the tank and found a little round piece of foil from an oil can stuck in it causing the restriction. I guess the issue was a combination of me not syncing the carbs correctly and the restriction in the fuel line. Boat has been running great for the last couple of months and I wanted to post in case anyone else ever had a similar issue.