bf 7.5 milky oil

I have search and also read the post today. I have a 1972ish bf 7.5 hp Honda motor. I had starting problems which were fixed thanks in part to JGMO. The motor idles great and runs great for a short period, but then runs rough at higher throttle and gets milky colored oil. I have seen recommendations to check the T-stat and maybe the prop shaft seal but, these were for larger motors. Are these common on the 7.5 hp motor as well?
TIA!

Small motors are just like the big ones in many areas, including the T-stat and prop shaft seals. Make sure you let it sit for a while before checking the gear oil. Little bubbles form while running the lower unit making it look milky. I don't know the story of what you have already done. Rough running can be caused by a lot of things. The basics are check compression, check for strong spark with a spark tester, check the fuel system to make sure it is delivering correctly. A bad connections, cracked hose, pinhole in the fuel pump, or dirty carb can make it run rough. With a 4 stroke you also have more parts to diagnose beyond the basics, like the valves, timing belt, etc. I would start with the easy stuff and work from there. My guess is carburetor or fuel line connections. Give us some more details so we can help.

To clarify this is engine oil not gear oil that's turning milky. I thought maybe a head gasket or something on the motor not the lower was the problem. The engine idled and at slow speed was fine, I only shut it off when i noticed the milky oil dripping out the rear drain holes on the case. My guess is the motor will start right up if I try. The motor idled fine but ran rough when at higher throttle. I thought maybe the milky oil was getting by the rings some and fouling the fuel. I was hoping that there was a common problem that people were aware of or that someone can point me in the direction of what to look at and check first.

Hondadude could probably tell you exactly what it is the first try, but it doesn't sound good if you are getting milky colored engine oil. Have you completely changed the oil in the powerhead? There should not be any water in any of the same compartments that the engine oil is in. You may have a crack in the block or a bad head or waterjacket gasket that is allowing water from the cooling system to enter the combustion and lubricating areas. That would also explain the rough engine at higher speeds. It would just make the cross contamination more extreme. I would recommend a compression test to see if one cylinder is worse than the other. From there it is replacing the head gasket and waterjacket gaskets. Did this engine ever overheat?

I did drain the oil and replaced with new prior to my last outing when I noticed the milky oil. I got this motor used and was told it ran before storing. It looked clean and started very easily after fixing the fuel issues and timing. I have no other info on it other than the work I have done. I will check the compression after I pick up a gauge. I did plug with my finger and got something.

You are getting some compression or it wouldn't run at all, but the only way to really check it is with a good compression tester. This is a must have tool if you are working on any engine. When you get your tester. Pull both spark plugs and leave the out. Put the tester in one hole snugly and pull the rope nice and hard 3 or 4 times. Write it down and do the other. They should be fairly close in PSI to each other and within the specs for this motor (which I do not know off the top of my heaad) probably above 90 psi.

I haven't gotten around to picking up a compression gauge just yet. I went ahead and changed the thermostat, gaskets, and oil. I started the motor and noticed a small stream of water coming out next to where the hose that comes from the thermostat and goes to the dip stick area is. Needless to say the oil and water are still mixing. It seems like said hose maybe connected in the wrong location. I checked the hose routing in the manual and there is conflicting information. I have 3 ports on the dipstick plate and the manual doesn't show any on my model. I have 1 large port on the left which is connected to the hose mentioned above. To the right there is a large and small port. Both the upper large and lower smaller port goes to the water pump. You can see the large ports has milky oil just above the hose in the picture. Why does water get routed through the dip stick plate?

I just sold my motor like that and wished I had taken a look first. The hose coming off the engine by the thermostat should not go to the dipstick area, but to the lower cowl on the tiller handle side there should be a place to hook it up as a water pee indicator. This is so you can see it is pumping water. The dipstick ports are probably breather lines that hook to the engine in a different place. It sounds like you are pumping water directly into your oil in the engine. Can you see where I am talking about hooking up the hose that has water coming out of it to the lower cowl indicator hole. With these motors the water kind of drops straight down rather that shoot out the side like an OMC or Mercury engine.

I will look again but I did not see any other empty places to hook the hoses to. I have a hose coming from the water pump for the pee indicator I agree it looks like my setup is pumping water in to the oil. This is how I got the motor. The pee is not mixed with oil and seems normal and has normal pressure. My current setup is hose coming from thermostat to the port to the lower left on the above picture. Small hose to the right goes to water pump. The port just above that also goes to the water pump. Then I have a hose from the water pump which goes to the opening which also lets the carb. drain fuel. I'm not sure but I think it's the pee hole indicator you speak of. I only ran the motor a few seconds and there was alot of water in the oil. It seemed like it was being pumped in. If it was a head gasket issue I would expect the water to be introduced more slowly.

The early versions of the 7.5 were different than the later versions.

What is your serial number? So I can determine what you have.

The later version has the hose that goes from the starboard side of the engine to the thermostat area. The water comes from the water pump and splits near the lower starboard side....part goes to the head and the other goes to the thermostat housing to the telltale, as thebubba, said. Some of it also goes to the exhaust to cool it down until the thermostat opens.

If it is the later version, it is very similar to the BF8. If so, check out this link and it will give you several things to check. http://www.marineengine.com/boat-forum/showthread.php?407490-bf8a

The later BF75 compression should be around 142 psi, with the throttle wide open.

Mike

My serial number is BF75 1100992 I have been told this is a 72-73 motor. It seems like it may be the O-ring under the filler neck. I saw a water stream coming out the side of the oil fill cover next to the hose.

It is a 1979. The model is BF75Z Use this model number to get parts.

When you take the fill off, if it is the plastic one, check to be sure it is not warped. If so, replace it as well as the o ring.

Mike

I replaced the filler and the gasket then ran it for 10 minutes and the oil was clean. Thanks HondaDUDE!

Glad things worked out.

Mike