Honda BF50 steaming from exhaust and losing oil

[phoenix777]

Hey All,
First off I am new to Hondas and relatively ignorant in some respects, but have worked on this boat some already and poured over a lot of threads. I spent more money on the boat and motor than i am willing to throw away from my own ignorance... I also bought it on an impulse as I thought it was a pretty sweet deal(3000boat, motor and trailer). Motor appeared to run great when I was buying it.. watched the guy I bought it from replace impeller the day I bought it. That being said got it home and realized it had no muffler assembly and linkage hadn't been re attached, Lets just say that the guy I bought it from also sold used cars... Realized I was dealing with a different animal than the simple tiller steer 2cycles I had before and i might be out of my element to a degree(mainly my wallet) but I can't really afford to take it to a mechanic so need learn how myself.

Motor issues
Steam is coming out of the exhaust after warm up both on muffs(taped the intake) and water out of the telltale can get pretty hot but not scalding, not steaming out of the telltale and pressure is good and consistent after initial startup. The head is hot once warmed up, not burning hot but too hot to leave my hand for long. The bottom end of upper cowling(near exhaust) is hot to the touch. I haven't had an overheat alarm go off since it has started steaming but i don't know if the alarm even works. It seamed to steam a little bit on occasion in the past but it is consistent the last few times out once warmed up and occurs at higher rpm and idle.

Also the motor loses oil at a pretty quick rate. I check it every time I go out and it seems to vary but I could easily put a quart in every 10-15 hrs.. On 2 occasions out of the many times out I have seen a small oil slick in water, but not any more than you might see on a 2cycle. When I installed the muffler I noticed a spray of oil in that area of the engine near carburetor but haven't noticed more since. Noticed on the muffs last week that there appeared to be some smoke out of the prop like a 2cycle might have been carbs from sitting a couple months but not sure. The oil loss is certainly abnormal. I'm down to learn and try and work this out myself, but I'm not sure where to even start. I'm also worried one of you is gonna say something expensive. Ive change oil and filter maybe 30 hours ago.



I am going to replace/rebuild water pump and impeller and thermostat in the next week but is there anything else obvious I could do to make sure I'm not going to burn engine up? As to the oil issue?
Thanks, I've learned a lot already from this forum.

 

[hondam]

Before you do anything else, a leak down test needs to be done and mechanical timing needs to be checked. That will tell you what kind of condition internally the engine is.

The "steam" your experiencing may not be an overheat situation, there are a couple things that could be causing this. Since your loosing oil, there is a high possibility this is the motor burning the oil which would cause it to smoke. Make sure the engine is reaching proper operating temp with an infrared thermometer and when your done with the motor do not leave it tilted all the way down, tilt it up slightly. Also the carbs require a different procedure and special tools to adjust correctly, it could be heavily flooding which would also cause it to smoke.

If you decide to replace the water pump impeller i would take a good look at the housing and bad, if its melted at all it needs to be replaced. Look into the housing from the top and if you see the housing melted where it meets the stainless liner it needs to be replaced. Also looking at the base from the top take a good look at the surface immediately surrounding the drive shaft, the edge should be square and not melted. If you have to replace the base, it does not come with seals so make sure you order a couple of those.

 

[tommarvin]

Wow, you have a project. Over heat is three things, water pump/ which is a rubber impeller, thermostat, put in a pan of cold water heat slowly, what temp does it open? lastly the sensor, test sensor you may have to ground the body, put end in warm water heat slowly ,our overheat buzzer sounds at 180F we have a force 125. You should never get to 180F at thermostat, an IR Thermometer is perfect for this aim at t-stat housing, HF has them fair price,

Losing one quart of motor every 10-15 hours I hope it's not going through broken rings.If you can't find a motor oil leak, you better do a compression test.
You always want to do a compression test, and check for water in the lower unit before you buy a boat. If the compression is bad can you go to small claims court? Do you have a lemon law where you live? Just go back to the guy and say you want your money back!

 

[hondam]

A compression test on most 4 strokes need to be done with the throttle linkage at WOT. This cannot be done without some manipulation. Doing it any other way will give you false reading so be careful.

Factory spec on that motor was 199psi

 

[tommarvin]

hondam, I didn't know you had to do a compression test on four strokes,with the throttle linkage at WOT,can you please share with us how to do it?.

 

[hondam]

There are two ways. Put the gear handle all the way wot, this can only be done while in forward gear so take the prop off, and use a starter button directly on the solenoid to bypass the neutral safety switch.

Two disconnect the throttle cable so you can work it by hand and have a helper crank over the motor for you while you hold it wide open.

Either way make sure all the spark plugs are out not just the one that your doing and if you have a shut down lanyard make sure it's not attached. Stay clear of the spark plug wires. There are a lot of safety concerns when doing a compression test that's one of the reasons i usually do a leak down test, it eliminates a lot of variables and to me since I've done a lot of them it's actually easier on 4 stroke outboards.

 

[tommarvin]

Thanks hondam, 4-stroke compression test are not easy, plus the safety concerns.
Feel like sharing how to do a leak down test, please

 

[hondam]

A leak down tester is a specialized tool, not to expensive, They range anywhere as low as $25 up to about $200 for a high end digital one.

Pull out the spark plugs, turn the engine over (i usually do it by hand, easy to do with the plugs out) until the cylinder that you are testing is on TDC, plug the tool in and read it.

The only complication is that a leak down tester requires an air supply, so if you dont have an air compressor handy you cant do it. What a leak down test does is it puts compressed air into the cylinder and measures how much of it is escaping.

 

[tommarvin]

Thank You, how long do you wait to read the cylinder leakage?

 

[hondam]

Its an immediate result