sandkicker
Outstanding Contributor
My BF75 ( 7.5HP long shaft S/N 150xxxx) which runs in salt water, has developed an appetite for T'sats these last 5 seasons. It came to a head last season when after only 3 hrs of operation ( and a mid season flush with a salt removal product) it started to run hot with a diminished output from the bypass hose.
Since there was evidence that during Hurricane Sandy ( after running warm incident) that storm surge "pooped" the boat in its slip, I decided to do a partial tear down of the engine. Apparently, the engine in its cover got pretty well splashed, but no water inside ( advance mechanism was a bit rusted). I decided that so long as I had the engine on the saw horse, that I'd pull the intake manifold.
My big surprise was that the T'stat itself was almost totally caked in salt. I checked the passage in the intake manifold that the bypass hose attaches to and it appeared to be plugged. After fooling with it for a time with wire, I decided to run a drill bit by hand thru from the inside to the outside to clear that passage. Then I discovered the problem. When HONDA makes these engines, there is a tapered hole cast into the intake manifold into which the tube that the hose attaches to is press fit. In order to make sure this is secure, HONDA slits this tube for about 1/4" on the manifold end, so that when the tube is forced in, the leading edge collapses in a "curl" insuring a tight fit. Which it does, HOWEVER, what it also does is convert that looks like a single hole into two holes with a divider between them. The smaller of these two holes plugs very easily.
This bypass hose serves two purposes.
1) indicator of water pump operation
2) DRAIN OUT PASSAGE for the intake manifold t'stat housing when you shut off the engine.
A partial blockage allows #1, above, to happen, but not #2! This will cause salt deposits to accumulate in and around the t'stat. BTW, an overnight soak in vinegar cleaned up the t'stat.
My fix,
1) I drilled out the sheet metal tube totally (turning drill bit by hand with a tap wrench)
2) purchased a nylon barb hose fitting ( <correct> tubing to 1/4 pipe)
3) Cut off the 1/4 male pipe fitting from the barb with an exacto knife leaving a short straight tube on one end and a hose barb on the other.
4) Threaded the straight tube. I ruined one before I got it right.
5) tapped the hole in the intake manifold that the old hose barb was force fitted into after "chasing" thehole withthe correct drill for the tap. Very little material is removed in doing this.
6) screwed the now threaded barb into the now tapped manifold.
7) After installation in the manifold, I used a larger drill bit in a tap handle, to carefully cut a slight chamfer in the manifold end of the new plastic bypass hose barb.
Since there was evidence that during Hurricane Sandy ( after running warm incident) that storm surge "pooped" the boat in its slip, I decided to do a partial tear down of the engine. Apparently, the engine in its cover got pretty well splashed, but no water inside ( advance mechanism was a bit rusted). I decided that so long as I had the engine on the saw horse, that I'd pull the intake manifold.
My big surprise was that the T'stat itself was almost totally caked in salt. I checked the passage in the intake manifold that the bypass hose attaches to and it appeared to be plugged. After fooling with it for a time with wire, I decided to run a drill bit by hand thru from the inside to the outside to clear that passage. Then I discovered the problem. When HONDA makes these engines, there is a tapered hole cast into the intake manifold into which the tube that the hose attaches to is press fit. In order to make sure this is secure, HONDA slits this tube for about 1/4" on the manifold end, so that when the tube is forced in, the leading edge collapses in a "curl" insuring a tight fit. Which it does, HOWEVER, what it also does is convert that looks like a single hole into two holes with a divider between them. The smaller of these two holes plugs very easily.
This bypass hose serves two purposes.
1) indicator of water pump operation
2) DRAIN OUT PASSAGE for the intake manifold t'stat housing when you shut off the engine.
A partial blockage allows #1, above, to happen, but not #2! This will cause salt deposits to accumulate in and around the t'stat. BTW, an overnight soak in vinegar cleaned up the t'stat.
My fix,
1) I drilled out the sheet metal tube totally (turning drill bit by hand with a tap wrench)
2) purchased a nylon barb hose fitting ( <correct> tubing to 1/4 pipe)
3) Cut off the 1/4 male pipe fitting from the barb with an exacto knife leaving a short straight tube on one end and a hose barb on the other.
4) Threaded the straight tube. I ruined one before I got it right.
5) tapped the hole in the intake manifold that the old hose barb was force fitted into after "chasing" thehole withthe correct drill for the tap. Very little material is removed in doing this.
6) screwed the now threaded barb into the now tapped manifold.
7) After installation in the manifold, I used a larger drill bit in a tap handle, to carefully cut a slight chamfer in the manifold end of the new plastic bypass hose barb.