Engine Bogs Down

[rmart]

This site has helped me time and again with questions re: a 1987 18' Outrage I purchased last year. Now, after my first run of the season, I am experiencing a frustrating engine problem with my 1987 Yamaha 115 that I thought had been resolved last year.<br /><br />The best way to describe problem is that the engine bogs down and sometimes stalls when I increase the throttle from a trolling speed. The bogging and/or stall can be minimized quite often if I click on the full choke switch at the same time I increase the throttle.<br /><br />What is most annoying is that I took this boat to a local marina last year in September and had the following work performed:<br /><br />(1) engine tune-up; (2) replaced spark plugs; (3) rebuilt carbs; (4) replaced water/fuel separator; (5) changed oil senders in both remote and main tanks; (6) changed lower unit oil; and (7) water test.<br /><br />Following this work the engine ran much better for the month of September 2002.<br /><br />However, this afternoon on the first day of use the engine is boggin down again. I am frustrated and don't know where I should start at this point and would greatly appreciate any suggestions. <br /><br />With an older engine like mine, I want to be careful in spending too much on repairs so your guidance on where to start and what I should anticpate in repair costs is greatly appreciated<br /><br />Thanks in advance.

 

[trumpetbucks]

Re: Engine Bogs Down

If the problem is helped by choke and/or full throttle, then it would seem the problem is a fule restriction somewhere.<br /><br />Check for some gunk in your fuel system. Could be anywhere between the tank and the carbs.<br /><br />Hopefully someone with a similar problem can give you more specific advice.

 

[dakk1]

Re: Engine Bogs Down

rmart<br /><br />BoatProject is right. The same thing happened to me. I also have an older motor, 1985 Merc 150. I had rebuilt the fuel pump and the carbs, put in new gas and oil and the first day out I had the exact same problem you describe. Although I still don't know how, I had water in the gas. At any rate I would suspect a fuel delivery problem. The fact that you can improve performance by operating the choke indicates fuel starvation. Especially since it ran good last season. <br />I removed the bad gas and tried again with a new remote 6 gal tank and I still had the problem ,to a lesser degree. Took another 6 gal. to clear it up. In your tune up list I didn't see anything about fuel pump. I'm sure you covered that though. Goog Luck!

 

[dcato]

Re: Engine Bogs Down

i have been having similair problems with my yam 225. tried cleaning the carbs, checking fuel lines, new plugs, etc. i believe the problem was water in the fuel. it doesn't take much to bog you down. not sure about adding dry gas to a 2 stroke but ask about it.

 

[kkip3816]

Re: Engine Bogs Down

I am currently having the same problem with a 1984 merc 150. It seems to run pretty well once I get up to high rpm's (4000 and above) but has a very difficult time in the mid range area. I have to choke it during acceleration to get from idle to plane speed. The problem seems to be getting worse as well. I have cleaned and rebuilt all carbs, adjusted float levels, rebuilt fuel pump, even experimented with slightly different jetting (compensation for altitude changes), and still have the problem. I did not try the complete tank drain approach to eliminate possibility of water in the fuel, although I go through fuel very regularily I guess there still could be some water in it. I will give it a try tomorrow and see if it helps. Has anyone had luck using a fuel dryer additive on these outboards? I use stabil before the end of the season to keep the tank fairly clean over the winter and then drain it at the beginning of each summer. I am running out of ideas but if anyone has suggestions it sounds like quite a few of us could use the help.Thanks,<br />Kip

 

[Bluefish]

Re: Engine Bogs Down

Try a premix of gas and oil in a spray bottle and spray into one crab at a time when engine is bogging down if rpms pick up that is the crab giving you the trouble. You can also install a clear line between primer bulb and engine to check for air bubbles a big problem for outboards it is best to check all the way to fuel pump remember you can be sucking air in and have no signs of a fuel leak.

 

[rmart]

Re: Engine Bogs Down

Status report. Ran the boat last night after de-carbing the engine with a can of ValveTech. Ran the engine on a new 6.5 gallon tank, new gas and new fuel line (with new primer bulb) running the new line directly to the engine (no water/fuel separator). <br /><br />Engine still bogged down while increasing throttle! <br /><br />Only help continues to be full choke toggle switch.<br /><br />Afterwards, changed the water/fuel separator and drained the old cannister to find no water or debris.

 

[kkip3816]

Re: Engine Bogs Down

rmart, sounds like we are in the same situation. I removed and cleaned main fuel tank, as well as checked all fuel lines and connections for restrictions or leaks. I tried it again yesterday with the same results. When I am able to get through the midrange acceleration using the choke, it will run pretty well on top end. But after letting it run fast for awhile it seems to run even worse at slow speeds and mid range. I have checked all compression (not great but within specs at 104 to 109 lowest to highest cylinder). I also removed and inspected all of the reed petals and blocks and they look perfect. Now I need some gaskets to re-assemble tomorrow. I found something today that may solve some of the problem, I removed and doublechecked all carbs. I found that the floats do not appear to be the exact same type that the manual pictures. The manual suggests a 1/16th inch drop from base of carb bowl to float base but the float is not flat on the bottom. It has a tapered rim. I slowly filled the bowls with fuel and noticed that they were shutting the needle valve off when the bowl was only half full. I adjusted all of the loats to allow a little more fuel into the bowls before closing the needle valve. I think that they may have been starving the main fuel circuit for fuel due to low float levels. The idle tube extends further down into the boal than the main pickup and it would make sense that the idle tube was getting fuel but the main pickup tube was having trouble. I am still experimenting but I will let you know if it appears to help. If I run out of ideas concerning fueld delivery, I guess the problem may lie in the ignition side (although all coils are firing even after the engine is up to temperature), I checked each one yesterday and had a strong spark on all 6 plugs. Does anyone have any other ideas?<br />Thanks,<br />Kip

 

[ntermini]

Re: Engine Bogs Down

Do you know where I can pick up some ValveTech

 

[ppresutticoast]

Re: Engine Bogs Down

I had a similar problem with my 2001 Yamaha. Checked for water in the gas....none found. Changed all plugs and water seperator. Still same problem. Turns out that my Thermostats in the engine were bad! They were telling the engine she was running cold. This then tells the computer to create an oil gas mixture that bogs down the engine. You can try just cleaning the engine thermostats. Sometimes a piece of sand can get in there and keep the thermostat open which can cause this problem. I simply changed my thermostats and she runs perfect. Try that! Thermostats were about $40 each and I changed both. Good luck.