Building a better 2.4 for Towing

[TTriton]

I have been looking for a way to build a better engine for towing. Our engine's often break the top cap and letting the top main bearing cock slightly sideways. Thus damaging the top main jurnal of the crank. This is a very common problem with our merc when we tow and put a bunch of stress on the engine's at low RPM's. Does anyone have an idea on how to stop this problem? Would light weight flywheels help stop this or balacing the rotating assembly? Any idea's would be great. And if anyone is intersted I have a bunch of cranks with top main damage that I would sell.

[Delta]

TTriton:
I realize ya don't really have time to swap props to get your towing rpms up,with a lower pitch,but it's a thought !
Good luck,Delta

[TTriton]

I have thought of this and even looked into the land and sea torque shift props to see if I can lock them in at the lower pitch and then when I'm not towing let them shift like they are designed to.

[mercrazy]

replace the oiler tubing going to the top bearing. light cranks might help too if you operate in rough water.

[TTriton]

Should I just use a stock size tube or is there a special tube to use? I've been using a fuel safe tube from the Remote control hobby store because it is strong and clear. I can see inside the tube to make sure there is no clogs and all is working OK. With the stock BLACK Merc tubes you have no idea if there is any oil inside

[RocketMan]

You've either got an oil feed problem to the top bearing or your captains are running at an RPM that is a bad resonance point. Try this if you already haven't:

Put the lowest pitch props on the motors that you can find and try 2:1 lower unit gears from a 150 V6. This should move your RPM up and get you out the resonant frequency that's taking out the top bearing and crank journal.

Make absolutly sure that the top bearing oil feed line is new and tight on the little check valve at the top bearing and bottom bearing. You should be able to blow into the top fitting but not be able to draw air out. The bottom check valve should be the oppposite.

Use the see-through yellow Tygon tubing from the Mercury High Performace motors, not the stock black stuff. When starting a fresh powerhead for the first time, make sure you see oil "pumping" or pulsing it's way up the yellow tubing and disappearing into the top bearing cap. If you don't see it in the tube after 5 minutes or so and the check valves are good > disassemble the powerhead and start over! You got some perfect seal, needle bearing assy. grease or "???" in the oil feed passages in the top and/or bottom bearing cap.

While in service check the yellow hose and check valves from time to time to see that oil is pumping. When hose discolors to the point you can't see through it, replace hose.

Lightning and balancing the big ass 40 amp flywheels is not a bad idea either. Balancing can change the resonant frequency and get you out of trouble. Light flywheel can make engines idle a little rougher however. For flywheel work, Contact Jamie Adams at

HYDRODYNAMICS,
520 Capital Drive, Pewaukee, WI 53072

1-414-691-1995 phone
1-414-691-1997 fax

Tell him Paul Messinger sent you.

Good luck,

Paul

[mercrazy]

that tubing is probably ok but i've never had a problem with new mercury tubing. does your tubing have the same inside diameter? if not, maybe that could have an effect on the transfer of fluid. most of the failed bearings i've seen were caused by the tubing being old and cracked or loose from the fittings or pinched. have you ever seen water in the bearing? might have a water leak that gets to the bearing or are your engines mounted very low on the boat? could it be coming in the exhaust port? make sure the fittings aren't clogged. make sure the holes are aligned properly from the block fitting to the bearing housing. check top and bottom fittings. flood the bearing with oil before initial startup. you say the cap breaks and lets the bearing cock sideways. are you sure the bearing isn't failing first, then breaking the cap? what part of the cap is broken? what rpm range have you been running in? the torque-shift prop is adjustable so it only shifts at higher rpms. you would probably never tow fast enough for it to shift.

[TTriton]

The ID is the same and this tubing that I am using is a new practice and I havn't has a engine fail yet since I started using it. And I'm not sure if this is alway true but I do know that they main cap had broken first. It the last engine that I had this problem with I found the broken cap before it damaged the bearing of the crank. I was working on something else when I looked at the flywheel and saw oil/fuel running out from under it. Removed the flywheel and found the main cap broke so bad I had to remove it in pieces praying not to drop any into the engine. found the bearing in good shape and the crank with no damage. repalced cap and main and it is still ont the boat now.