2GM20F engine issue

[Ken13559]

1. I've never had this problem before. But 2 weeks back, starting engine after sailing it gets overheated with alarm. Found U Mixing elbow hot. Pull out the SCW hose to pump to clear any airlock, then start engine and pull out the hose at heat exchanger inlet to make sure SCW is flowing then engine runs normally.
Thereafter I have checked all the hoses from water inlet valve right through to U Mixing elbow and couldn't find and issue. I even removed the Anti-Siphon valve for blow & suction test. All looks good BUT still engine gets overheat each time i start it. What gives?

2. Engine could not reverse normally. I might have damaged the gearbox last year when i shift engine into reverse while tie to the dock against a fast flowing river water. Engine reversing was trying to push river water back upstream! My mistake. After that whenever i shift to reverse, the engine gets loaded with black smoke and I need to shift to neutral, forward then reverse again before things works.
Now, one year later, engine totally won't do a sub-normal reverse (as described above), it will laboriously turn the prop very slowly puff out black smoke. I guess the gearbox is shot. So what broke in the gearbox? Any idea?

Thanks.

 

[Davidasailor26]

1. Have you checked the mixing elbow itself? It could be clogged and explain why all the hoses up to that point seem to provide good supply but once connected you have problems. Also have you checked the impeller to make sure it still has all of its blades? You could have reduced flow if a blade is missing or has lodged in the pump body heat exchanger. If you open the seacock quickly with no hose attached, or the hose held below the waterline do you get a really strong flow of water? Sometimes a partial obstruction will reduce the flow. Can you tell how much water is actually coming out the exhaust?

2. How fast was the current running? Shifting into reverse against a current shouldn’t really be any worse than shifting into reverse to slow the boat down when approaching a dock. Neither should do any damage unless speeds are really excessive. So I wouldn’t beat yourself up about having done anything wrong there. It does sound like something’s wrong in the gearbox though.

 

[Davidasailor26]

One other thought on the transmission - do you have a feathering prop? If so it could just be that the feathering mechanism is worn or fouled preventing the blades from feathering properly for reverse.

 

[kloudie1]

If you are sure the sea water side is free flowing, you could have a bad thermostat, water pump, loose belt on the coolant pump. fouled heat exchanger etc..
Reversing against current would not be enough to cause a transmission problem by itself.. If you are comfortable that the prop is clean and the shaft and cutlass are not fouled and (as David says) the prop is not malfunctioning ....
usually a failed transmission would be making some nasty noises ..

 

[dlochner]

Check the transmission fluid. If it is black you may have burned up a cluctch plate. Reversing into a current should not have damaged the transmission, unless there was some latent damage like worn clutch plates.

Check the shift cables to make sure they are still in proper adjustment.

 

[Ralph Johnstone]

Thereafter I have checked all the hoses from water inlet valve right through to U Mixing elbow and couldn't find and issue.

Check out your fancy SS mixing elbow for blockage. If it is blocked, please don't tell me. I'd rather live in ignorance and be happy.

If I remember rightly, it was your glowing description of the SS mixing elbow that fired me up to invest in one. That was just before you developed the corrosion hole in the side. I've been doing great for years with the elbow ...........

Ah, what the hell, if it's plugged tell me about it. I guess I'd rather know the truth than be known as a happy ignoramus.

Please don't take my ribbing seriously. It's problems like this that keep us so highly sought after in the cocktail circuit. They all love us when we REALLY open up about sailing rather than just replying with a simple "Meh"

 

[rgranger]

I’m so confused

 

[Ralph Johnstone]

I’m so confused

You would have had to live through it to understand it and even I still have quite a number of questions.

 

[Ken13559]

Ralph,
1. I've taken out the SS U Mixing elbow and it's full bore! No fouling or rust or carbon crust of any sort. My final assessment is it's likely the anti siphon valve that's not behaving. I guess while sailing the Venturi effect drains the exhaust of water hence air pocket.

2. The River flow was really fast, guestimate 3kts+. In any case I'll get the gearbox overhaul.

Ken

 

[Ken13559]

One other thought on the transmission - do you have a feathering prop? If so it could just be that the feathering mechanism is worn or fouled preventing the blades from feathering properly for reverse.

Yes! I do have a feathering Kiwiprop. Things is, this prop blades are free flipping. Going forward no issue.
Never had this problem till I made that mistake of reversing against the River flow. Now I'm pretty the the gearbox has a problem.

Ken

 

[Ken13559]

Mechanic took away my gearbox for repair 2 days ago. Had to chip away the engine bay fibreglass ridge in-order to move the shaft couple back enough to remove gearbox. Now there's exposed balsa core in the fibreglass. What can I use to water-proof the balsa core and epoxy up the ridge?

 

[dlochner]

Saturate the raw balsa with neat epoxy. Then it will probably be necessary to replace the fiberglass. A few photos would help.

 

[Ken13559]

Saturate the raw balsa with neat epoxy. Then it will probably be necessary to replace the fiberglass. A few photos would help.

Will get some photos this weekend.

 

[Ralph Johnstone]

Hi Ken,

System three is what I have always used from glass repairs to waterproofing balsa core material. I think they're all just about the same but this one has an excellent instruction book that goes along with the material.

I've cut several holes in the hull and cabin structure. Any thru hulls are soaked with thinned epoxy to saturate the balsa before the SS thru-hull in installed.

See page 11 and do a search for "thinner" which is up to 10% lacquer thinner which gives the epoxy the viscosity of water. After the balsa is soaked, eliminate the thinner and the viscous epoxy can be used with glass cloth to build up the ridge.

The Cliff's Notes of the manual says to keep adding coats of epoxy once the under coat is sticky to the touch so you can move fairly quickly when it's warm outside.

 

[Ken13559]

Had to chisel off the ridge to move the shaft flange back so that gearbox could be be removed. I should have loosen the engine mounts and lifted the engine some instead but what's done is done

 

[Ken13559]

Now I'm back to square one! The repaired gearbox didn't solve my reversing problem. Now I'm thinking perhaps its due to low compression of the engine....piston & scraper rings wears?
I'll try to adjust the tappet gaps and do compression test in coming weeks. I know for sure the compression pressure wasn't up to spec since several years back but never put much thoughts into it....till now.

 

[Davidasailor26]

If there are no problems in forward I wouldn’t assume compression is an issue. I’m still leaning towards an issue with the feathering prop somehow jamming in reverse.

 

[Ralph Johnstone]

Had to chisel off the ridge to move the shaft flange back so that gearbox

@Ken13559 , if you haven't started the repairs on the little dam, use a glue gun to set up a temporary retainer around the chiselled wood for the thinned epoxy and then pour the thinned epoxy to it. DON'T build up the original dam to its original height as who knows, someday you may be doing the same thing again and it's best to leave the engine alone once it's aligned.

The repaired gearbox didn't solve my reversing problem. Now I'm thinking perhaps its due to low compression of the engine....piston & scraper rings wears?

Ken, do you have a theory as to why the low compression may be what is preventing the transmission from shifting into reverse ? I fail to see a relationship between the two, but that's just me.

Keep us informed of every detail on the mechanical problems as you go along. I can imagine how you feel. It seems like a lonely, miserable, SOB right now but we're all with you on this.

 

[twodzusfittings]

Two things come to mind. First in regards to low compression is, make sure your compression lever is fully closed. Secondly: Have you recently adjusted your shaft boot seal? Have you made it too tight, so much so the shaft isn't turning freely?(Therefor the low rpms)

Dont bite my head off, just thinking outside the box, so to speak!

 

[Ken13559]

@Ken13559 , if you haven't started the repairs on the little dam, use a glue gun to set up a temporary retainer around the chiselled wood for the thinned epoxy and then pour the thinned epoxy to it. DON'T build up the original dam to its original height as who knows, someday you may be doing the same thing again and it's best to leave the engine alone once it's aligned.

Thanks for this idea.