HELP! 4JH-TE with KWB-20 transmission Problem

[Grasails]

Hello all, Any advice "Much Appreciated Thanks"
I have a Yanmar 4JH-TE with KWB-20 transmission everything has seemed to run great for the last 12 months, yesterday I was out on the boat for a maintenance run and when I engaged forward, the boat didn't seem to have the push it usually has, my first thoughts were weed around the prop, the problem seemed to just get worse, I couldn't get the rpm over 1800 and the engine was labouring, but the boat still had very little speed 2KTS usually at 2000rpm I would be at 5.5 kts, engine was labouring hard but when I engaged reverse there was no labour on the engine and it seemed OK, revving to 3000rpm no problems without labouring, I dropped anchor and jumped in the murky water to see if there was a fouling of the prop, all seemed Ok. I lifted the floor and could see some red oil at the bottom of the bilge, The KWB-20 uses ATF, the oil in the bilge was about 50mls 2-3 oil caps full, any help to fine the problem would be much appreciated.

[markxengineerin]

Did you check the oil level in the KB-20?
Suck the oil out with a hand pump and look for metal shavings?
Those would be my next steps.

The transmission may be easier to remove than you might assume, takes me about 45 minutes on the non-turbo version in my Pacific Seacraft. Pretty much just remove the shift linkage then the bolts holding it to the engine block + driveshaft flange and a strong person can pick it right up and out.

[skipperpete]

Do you have a fixed blade prop or feathering/folding type? Try rotating the propeller shaft manually with the gearbox in neutral to see how tight it is and finally check if the selector fully engages the selected rotation. Does the ATF smell burnt on the dip stick?

[skipperpete]

It’s confusing that the engine is laboring and not achieving normal operating rpm, a slipping “ahead” clutch would allow the engine to spin up to max rpm, there must be some sort of parasitic load that doesn’t exist in astern. Any bearing seizure in the gearbox should remain, regardless of what rotation is selected....... it’s a constant mesh transmission where everything spins all of the time when the engine is running

[Grasails]

Hi Mark and Pete, thanks for your advise, ive been back to the boat today, all fuel filters replaced. I have a folding prop, propellor shaft spins easily by hand, after what you said Pete parrasitic load! Could a cuttless bearing cause this when the prop starts to spin up load, braking the propellor shaft the higher the RPM ?

[Grasails]

Oil level in transmission was low, colour was red with a tinge of brown, didn't smell burnt but maybe hard worked, not metal fragments came up on the pump all clean other than a slight brown tinge, I refilled with clean oil

[skipperpete]

Originally Posted by Grasails

Hi Mark and Pete, thanks for your advise, ive been back to the boat today, all fuel filters replaced. I have a folding prop, propellor shaft spins easily by hand, after what you said Pete parrasitic load! Could a cuttless bearing cause this when the prop starts to spin up load, braking the propellor shaft the higher the RPM ?

There’s a chance that it’s a delaminated cuttless bearing that wedges the propshaft in ahead but allows it to spin easily in the opposite rotation and while I’ve seen a lot of collapsed rubber bearings, I’ve never even heard of the propshaft being partially and temporarily seized by one. There’s a possibility that there’s something going on with the drive plate but I’m more inclined to think it’s an engine problem, a loss of power would be obvious in forward but in astern it goes up to normal rpm because ..... A. The folding prop blades close up and the pitch is dramatically reduced and. B. Some reversing gears have a different reduction in astern and yours is 3:1 while ahead is maybe only 2.6:1 or less [ATTACH]

[Scubaseas]

The stuffing box would have the same resistance in either F or R. If you can turn the propeller shaft by hand and have a drip or two of water now and then it's not the stuffing box. If it was binding it would also be getting very hot to the touch.

From your description it sounds like the prop is not unfolding all the way. An over pitched prop would give you the same symptoms you describe. Maybe one of the blades is not fully unfolding?

Either that or somehow you are partially engaged in reverse while in forward.

If you put the transmission in neutral and run the engine does the propeller shaft turn?
You have friction and steel discs clutch packs just like most automatic automobile transmissions. It's possible that reverse clutch pack has an issue where reverse works fine but if partially engaged in Forward would create friction. I would expect black or very dark and burnt smelling fluid in this case though. I've seen this a lot as a mechanic. The friction material on the disc delaminates and the pieces jamb the clutch pack making act like it's engaged.

The small amount of oil in the bilge could be from the transmission overheating. You see this on cars towing heavy loads up long hills. The transmission "throws up" a small amount of fluid. I'd still look hard at the prop not unfolding all the way.

Fuel restriction might be the culprit. I know my boat needed all the fuel lines cleaned/replaced as there was rust particles at nearly every 90* elbow. Two of my three tanks were nearly completely clogged at the top of the tank where the pickup tube makes a 90* turn. You could rig up a separate diesel tank like a jerry jug connected directly to you filter and return lines to rule out a restriction upstream of your filters. The black steel tanks Tayana used tend to generate rust particles everywhere which act like a clogged filter.

Al,
V42CC #098 Sanctuary

[Grasails]

Thanks Al, and thanks for replying, On the gear selection lever there is about 3" or 75mm movement to engaged forward, when selecting Astern there is about 1" 25m movement to engage astern, if thevtransmisson has leaked oil would that mean a seal has failed and the transmission needs to come out, in Neutral the propshaft spins slowly anticlockwise and i can easily stop the spin with light pressure from my fingers, I will rig up a some kind of day tank to eliminate contaminated fuel as a culprit, I will look at the gear selection adjustments and see if it needs moving, and I will jump in and inspect the prop when the water clears a bit,
Cheers Gra

[Scubaseas]

"but the boat still had very little speed 2KTS usually at 2000rpm I would be at 5.5 kts, engine was labouring hard but when I engaged reverse there was no labour on the engine and it seemed OK, revving to 3000rpm no problems without labouring..."

This points to prop. If you have a folding that doesn't open all the way would account for all your symptoms. With the motor off and in neutral if you can easily turn the prop shaft by hand that should rule out the cutlass bearing or an issue with the stuffing box. Fuel starvation could limit the speed but you should still see close to 5kts of boat speed at that RPM. Something is wonky with your prop would be my bet. I have a folding prop that sat in the slip for 2.5 years. I could get 2800rpm but only about 3.5 kts boat speed when it would be closer to 7.5kts at that rpm. And I had pretty much zero reverse. There was a barnacle growth that kept the prop from fully opening. Also keep in mind that on a folding prop reverse may not be great even if everything is working OK. Best of luck with it. Curious to know what ultimately solves the problem.

Your oil may have been pushed out the vent. If the transmission got very hot this might be possible. If it's a seal it should keep leaking when engaged. Time will tell. The trans comes out pretty easily if you can get to it. My center cockpit takes a bit of boat yoga but it's doable. Use Locktite (blue 242) on everything not only for vibration but as anti-sieze. If you're pulling the transmission check how new are your motor mounts. Good time to change them and realign things if you have the reduction gear out.

I'd look at the fuel pick up piping just because it's a Tayana. What hull # are you?

[Grasails]

Al thank you, and Pete and Mark Thank You as well, so good to be able to tap into other peoples advice and experience,
TYA 42174F091
aft cabin, new filters and a fuel line clean wont hurt her I don't think, did notice a couple of small barnacle clusters, one on the tip of the Rudder, I bet you are right Al, a closer look at the prop is needed for Barnacles as the current was strong and water murky I may have missed a barnacle cluster as I was expecting rope or net or a bag fouling the prop, Black Iron Tanks are an issue its my next head ache "what To Do About the Tanks" I will post the outcome for sure

[Scubaseas]

1991 issue Hull #174. Excellent boat. Aft cabin makes some things easier, some things hard to get to. Add to that there was no one single interior they followed, and I've seen several different layouts. Some fuel tanks are a bitch to remove. Others like my two side tanks are fairly easy. I've got an 85-86 and thankfully the fuel tanks don't leak...yet. But I'm going to pull them and have them coated. The previous owner had lots of chronic fuel starvation issues. I started at the fuel tank and worked my way aft. The elbow at the tank pick up tube was clogged with fine rust and some sand on all three tanks. I've since added fuel shut off valves at the tanks per ABYC and replaced all my lines and hoses. I can say nearly every hose on my boat was original and almost all of them were hard as a rock or leaking. Have fun doing boat yoga. If you're not a member yet there is an excellent Tayana Owner's Group. It's mainly T37 people but there is some really good info on V42s. Tayana Owners Group Newsletter

[Scubaseas]

And the discussion board is at https://groups.google.com/g/tognews

[Grasails]

Well here us the round up parasitic drag 100% caused by some kind Of rusty crab pot steel mesh stopping the feathering autostream prop from fully engaging, cleaned bind of wire off the prop and a general scrub of the rudder and anodes and she's running great, very Happy also changed all my oils and filter and coolant its a win win win, Thanks for helping me sort out the issue everyone and Thanks Al you were all over it like hands on a cookie jar, I will join that Tayana group asap cheers and thank you

[Scubaseas]

De Nada. Glad you got it sorted out. If I ever get to Oz you can buy me a beer.

Look at the info on stuffing boxes and download it to keep with your boat docs. I have seen two V42's badly butchered because the yard was clueless about how it goes together. Another that was delayed because no one knew the stud threads were 1/2 X 13 British Standard which have a different pitch than US NC. Ditto a Rudder drawing for the V42. As stated, most of the info is T37 specific but if you poke around enough, you'll find some good info on the V42 and see where my lobsta pawt preventah came from. Ay Uh.

I have an Autostream on my Pearson. Nice piece of kit.