150 Yam Fuel Delivery?

[Parkhil2]

I have an 86 150 that is running very badly. The motor sat for 2-3 years, but was maintained and stored correctly. At the suggestion of those on the board, the carbs were removed, dissassembled, cleaned and reassembled, other that some clogged idle jets, the carbs were real clean. The motor has good compression on all cylinders, spark to all plugs. Yesterday It was idleing, very rough, so I decided to start pulling plug wires to see which cylinders were firing, basically only the top cylinder on each side was firing. I then flipped the fuel pumps, top to bottom, and the motor ran about the same, but now when I pulled the plugs on the 2nd cylinders from the top it seemed they were firing a little bit, not as effectivly as the tops, the tops were still firing as they were previously. Does anybody have advise, suggestions on where to start, I have a lot of money into the boat(Rebuilt the Transom) and would love to get some use out of it this summer. Is there a way I can varify that it is a fuel delivery problem, and not something electrical? Any and all help is appreciated.

 

[bigbrownbuku]

Re: 150 Yam Fuel Delivery?

did the carb link and sync get done correctly? i would start there.

 

[Ray Neudecker]

Re: 150 Yam Fuel Delivery?

Start by bypassing the fuel line quick disconnect and the engine mounted filter. They have both been sources of problems on those motors. The filter housing Often causes a restriction on those models after long periods of non use. You need to replace the fuel pumps and likely the fuel line and bulb.

 

[Parkhil2]

Re: 150 Yam Fuel Delivery?

Thanks, I will try all of the above today and post back how I make out. Is it okay to spray fuel into the carbs to see if it is a fuel delivery problem? Could this cause any damage?

 

[Ray Neudecker]

Re: 150 Yam Fuel Delivery?

Fuel or carb cleaner sprayed into the throats will work fine for that test.

 

[Parkhil2]

Re: 150 Yam Fuel Delivery?

I had a chance to bypass the quick connect and the fuel filter, with no better performance. I also tried spraying carb cleaner in the throats of the carb on the cylinders not firing, and didnt get any difference. For the heck of it, i compression tested all cylinders one more time, all were right at 90 psi. Tomorrow I am picking up the fuel pumps and replacing them, even if this is not my problem they shold be done anyway. The motor is still acting the same way, while running pull a plug off either of the top cylinders, big difference, pull a plug off either of center cyliners, minor difference. Pull one off bottom cylinder, no difference in how it is running. Any suggestions, or do I need to wait to rule out the fuel pumps first? I appreciate any and all help.

 

[Ray Neudecker]

Re: 150 Yam Fuel Delivery?

Since the compression is equal, you are down to fuel and fire as the problem. By far the most likely culprit will be fuel. I would change the pumps before trying to trouble shoot further.

 

[Parkhil2]

Re: 150 Yam Fuel Delivery?

I replaced both fuel pumps yesterday. Again I pulled one of the bottom cylinder plugs and noticed no difference in the running of the engine. If i pull the top cylinder plug wire I hear a huge difference in the performance, put that back on and pull the middle wire, less of a difference, put that back on and pull the bottom wire, no noticable difference. However, if i pull and leave off the top and middle wire, then pull the bottom I notice a difference in running of the engine, leading me to believe the cylinder is firing. Are the carbs not adjusted right? should this be happening? The carbs were disassembled and cleaned by me. All the fuel air screws were backed out 1.5 turns, about what the were prior to disassembly. What should I do next, or is this proper performance.

 

[Parkhil2]

Re: 150 Yam Fuel Delivery?

ttt

 

[Ray Neudecker]

Re: 150 Yam Fuel Delivery?

Time to give some in the water info. Very limited info from pulling plug wires while on the hose.

 

[Parkhil2]

Re: 150 Yam Fuel Delivery?

What should i be looking for on the water? Should I be pulling plug wires at idle in gear? in nuetral? with some throttle? Also, this might be a dumb qeustion and the source of all problems, but when the carbs were removed, no changes were made to any of the idle adjustment, butterfly adjustment, ect. So when put back on the motor these things were in the exact configuration as when removed, all butterflys are closed at idle, ect. Do you think I should follow the clymer manual instructions and make all the carb adjustments? Also should I re-shoot the timing? I was told by the person that gave me the boat that it ran well when stored 3 yrs ago?

 

[Ray Neudecker]

Re: 150 Yam Fuel Delivery?

Following the link and sych adjustments would be a good idea. Also turn the air idle adjustments all of the way in and back out 1 1/4 turns. Pulling plug wires on the water will more likely cause you to hurt yourself than do any good. Observe the idle and the boat through planing off. If it surges at any time, then back to trouble shooting the fuel delivery system, otherwise you should be good to go.

 

[Parkhil2]

Re: 150 Yam Fuel Delivery?

Will do. Going in the water Saturday. I'll let you know how it goes. Thanks alot for all of your help. I guess pulling the wires while swimming behind the boat is only good for the latter part of the fishing trip. LOL. Thanks again.

 

[Ray Neudecker]

Re: 150 Yam Fuel Delivery?

Never pull the plug wires while you are in the water. When the CDI units first came out, I unfortunately saw a Mercury Factory racing tech die from this at a race when he grounded out the multi thousand volts with his body. Be very careful about pulling on plug wires.