Honda BF75 Hot and Weak Telltale

[presleymarkw]

I bought this engine a year or so ago. Its been abused pretty hard but has perfect compression. Been fixing it up, even had the wrong carb when I bought it, turned around backward so the linkages would fit. Very inventive mechanics.

So when it stopped peeing I went right for the impeller. The impeller cap was in very poor condition. Seems to have been exposed to some high heat. Seemed like parts of the cap had melted and there were rough obstructions that were eating away at the impeller. Flexible impeller so someone had replaced it knowing the condition of the cap. Even the water channel cover next to the cap was malformed. Definatly small bit were being abrased off the impeller, not real bad but bad enough.

I replaced the cap, the cover and the impeller. Still wouldn't pass water, so I decided (incorrectly) that it must be the thermostat and pulled off the intake manifold and inspected the water channel realizing the telltale isn't inline with the thermostat. Replaced Thermostat and gaskets and the warped studs. Doing this I blew out the Telltale hose and a bunch of muddy gunk came out.

Still didn't pass water. Took me allot of pouring over parts diagrams to realize I missed replacing the water tube seal that sits on top of the impeller cap. Ok so now it passes water again.

However when I run it for a while the Telltale output starts to decrease and almost to a stop. I notice some holes that are on the midsection that start to put out steam. Don't know if this has an overheat alarm but I stopped it immediately at that point. The telltale water was very hot compared to the water in the trashcan.

I started it again next day and could see the same symptoms start. When its cold the stream is strong. As the engine runs for a good 10 to 15 mins the pressure from the telltale decreases and the water starts to get warm. I dont push it to where it almost stops.

I see two possibilities. 1. new thermostat is defective or I installed it wrong some how. 2. There are impeller bits in the block affecting flow.

I think my plan is to take off the intake manifold and if thermostat is fine then drop lower unit and hook up a hose to the water tube and try to wash impeller bits out the thermostat port.

I am now thinking my water issue has started because of impeller bits. Any tips to addressing something like this?

 

[racerone]

Running in a test bucket ?----Water must be 6" above the impeller.

 

[presleymarkw]

arped stu

Running in a test bucket ?----Water must be 6" above the impeller.

I have seen this but probably not really 6". I did wonder about this when the water was not flowing but that turned out to be the water tube seal cause I replaced the cap. It has always passed water fine in the trash can and is now. Only when it starts to warm up is there an issue.

It is also not the exhaust warming the water. The water in the can is very cold, the water from the telltale will eventually get very hot and almost stop.

 

[MattFL]

Stick a long piece of weed whacker string up the telltale and poke it around, while the motor is running, and see if you can dislodge anything. You might just have a lot of debris in there that starts to build up while it runs.

 

[racerone]

Up to you to test with water at least 6" above the impeller.-----Too many exhaust bubbles means you will have trubbles.

 

[presleymarkw]

Up to you to test with water at least 6" above the impeller.-----Too many exhaust bubbles means you will have trubbles.

It's not the level of water in the bucket. The level of the water in the bucket does not change over time, the flow of water and the temperature from the telltale does. I have run this engine in this can so many times for longer.

After many hours of research I am pretty confident this is a blown head gasket. I am going to retest compression. But even if that is good it's still probably the head gasket.

Besides the symptoms I mentioned here, there is a variance or pulse to the water output. This could be due to the water level in the bucket so if I don't have low compression I will test it on the water.

If you haven't heard of Danger Marine on Youtube he has some excellent info. Every time I go there looking for the hard answers I seem to find it. He mentions these symptoms very specifically in two different videos on cooling and head gaskets.

 

[MattFL]

If you can get your hands on a leak down tester, you can pressurize the cylinders and you might be able to hear where the air is leaking. You could remove the thermostat or exhaust plate if there is one and possibly hear the air leaking into the water jacket area. Also that cylinder would show more leakage on the gauge.

 

[presleymarkw]

Up to you to test with water at least 6" above the impeller.-----Too many exhaust bubbles means you will have trubbles.

Ummm... ok. Maybe it was cause I was running in a can. Compression test is fine same as before. Ran it on the water all day it purred like a kitten telltale never got hot or weak or did any pulsing. So umm... I owe ya a beer?

 

[Cpotts]

I've got the same problem on my 1983 BF75L. telltale is decently strong, but the water is really hot after about 3 minutes the engine dies. It's in a big bucket with water level nice and high.
I removed the inlet manifold and there's no thermostat! and it's pretty dry in the housing. I'm guessing it's overheating.
I was trying to trace the water pathways and using my compressor to blow them out. looking at the manifold itself, I don't see a pathway for water to even get to the thermostat.
I need help figuring out why the thermostat pathway is dry and how is water supposed to get there in the first place..

 

[flashback]

I've got the same problem on my 1983 BF75L. telltale is decently strong, but the water is really hot after about 3 minutes the engine dies. It's in a big bucket with water level nice and high.
I removed the inlet manifold and there's no thermostat! and it's pretty dry in the housing. I'm guessing it's overheating.
I was trying to trace the water pathways and using my compressor to blow them out. looking at the manifold itself, I don't see a pathway for water to even get to the thermostat.
I need help figuring out why the thermostat pathway is dry and how is water supposed to get there in the first place..

Probably want to start a new thread Cpotts, it would be more relevant...

 

[presleymarkw]

I've got the same problem on my 1983 BF75L. telltale is decently strong, but the water is really hot after about 3 minutes the engine dies. It's in a big bucket with water level nice and high.
I removed the inlet manifold and there's no thermostat! and it's pretty dry in the housing. I'm guessing it's overheating.
I was trying to trace the water pathways and using my compressor to blow them out. looking at the manifold itself, I don't see a pathway for water to even get to the thermostat.
I need help figuring out why the thermostat pathway is dry and how is water supposed to get there in the first place..

So ya I did all that too. You can DM me as well. Its because the telltale can still flow with the thermostat closed. The telltale does not ensure water is flowing and cooling your engine. It can give you and indication it may not be. But reality is once water comes up the pickup tube it slits. One path through the thermostat the other through the telltale. This is why they aren't connected when you look under the manifold.

So first get a thermostat. Cheap and easy and you already opened it.

Then stop running it in a bucket once see water flowing. Test it in a body of water. If you dont have the engine deep enough you dont have enough pressure for the water pup to do its job right. I would expect it to overheat heat running in a bucket in about 3 mins working normally.

I did not want to believe it but its true. Even running it in a trash can it will overheat. In the lake its just fine. There is a post above where I grovel that he was right.

 

[presleymarkw]

So ya I did all that too. You can DM me as well. Its because the telltale can still flow with the thermostat closed. The telltale does not ensure water is flowing and cooling your engine. It can give you and indication it may not be. But reality is once water comes up the pickup tube it slits. One path through the thermostat the other through the telltale. This is why they aren't connected when you look under the manifold. But it is likely your water flow is just fine if you see the tell tale flow.

So first get a thermostat. Cheap and easy and you already opened it.

Then stop running it in a bucket once see water flowing. Test it in a body of water. If you dont have the engine deep enough you dont have enough pressure for the water pup to do its job right. I would expect it to overheat heat running in a bucket in about 3 mins working normally.

I did not want to believe it but its true. Even running it in a trash can it will overheat. In the lake its just fine. There is a post above where I grovel that he was right.

 

[presleymarkw]

I need help figuring out why the thermostat pathway is dry and how is water supposed to get there in the first place..

for the thermostat as I remember that path is internal to the block. The pickup tube comes into the block and splits. One path to the internal thermostat passage. When the thermostat opens the water is allowed to flow essentially back into the block through another passage as controlled at the thermostat which allows water to flow cooling the block and exiting through the exhaust.

for the telltale once it splits in the block it comes out the Starboard side of the engine into a tube that runs over the top of the engine, into the manifold. That passage does not connect to the thermostat passage as it might appear it should. It passes through the manifold and out a nipple to your tell tale tube.

I did run a hose to my water pickup tube, and watch it come through my telltale because I wasnt getting any at the time. But you could do the same with the manifold off and watch it run out the thermostat cavity. That would ensure you have flow there.

 

[Cpotts]

thanks for the reply flashback. I've got it in a large garbage can with the water level over 6inches above the pump.

where the pump line splits between telltale/block, I suspect I have a blockage to the block side.

 

[presleymarkw]

thanks for the reply flashback. I've got it in a large garbage can with the water level over 6inches above the pump.

where the pump line splits between telltale/block, I suspect I have a blockage to the block side.

If you have water flowing go put it in a lake before you make another decision. I would have sworn the same thing. Then if you have the same issue worry about it then.

I literally had every symptom of a blown head, I had convinced myself. In a trashcan that deep as well. It was a little longer than 3 mins though.

 

[Cpotts]

If you have water flowing go put it in a lake before you make another decision. I would have sworn the same thing. Then if you have the same issue worry about it then.

I literally had every symptom of a blown head, I had convinced myself. In a trashcan that deep as well. It was a little longer than 3 mins though.

I don't have a boat..just.the.kicker

MOD EDIT: @Cpotts Adding your issue onto another person's thread is a hijack. Please review the forum rule on hijacking and feel free to start your own thread.