Help - Magnum 40 Blown Reed Blocks

[riddert]

I have two 1993 Mariner Magnum 40 engines that I bought for parts from different individuals. The first engine started making a ton of noise in the powerhead and then owner shut it down. I did a tear down and found one of the reed blocks had come into contact with the crank and tore the steel plates above the reeds right off.

Second engine I have not torn down yet but apparently still runs without noise. The problem is there is a hole in the crankcase just below the bottom carb. I am expecting to find a blown out reed block there as well, but not 100% sure yet.

In both cases, the owners had just replaced the water pump impellers which I found to be an interesting coincidence...

I guess my questions are:

1) Is this a common problem with these motors and/or is there a trick to servicing the impellers? Could it be that when the drive shaft is inserted from the bottom it may actually push the crank up slightly - just enough for the crank to come into contact with the reed plates and cause damage? Or is this perhaps just a bad design? The only thing holding the reed cages in place is one a small alignment pin on the cylinder facing side of the cage. I can say that the outer case (carb side) does not "Clamp" them down firmly because I could wiggle the reed cage through the carb hole before I even unbolted the case. Seems like a pretty flimsy design to me since they really are just "Flaoting" in there on the crank. Maybe there is a way to tighten them up with shims etc?

2) Second question is in regards to saving this engine block. The small machined hole in the cylinder block where the alignment pin I mentioned above is installed is pretty torn up now. Can this be welded up and re-drilled and/or can I get away with JB weld? It is a very thin area with hardly any metal to work with. Maybe better to scrap it?

Any help or your experience with a similar problem that you fixed would be really helpful. Have to decide if I should try to fix or just part out. Thanks!

 

[Laddies]

Re: Help - Magnum 40 Blown Reed Blocks

1. It's not a common problem.
2. If assembled properly the case will hold the reed blocks firmly.
3. The blocks can be repaired by a good machinist, by welding and line boring epoxy won't last.

 

[riddert]

Re: Help - Magnum 40 Blown Reed Blocks

Thanks for your responses. I am still at a loss though as to what is causing this. My second engine I have verified now has the same problem and I see there are other cases on the net as well with 1993 - 1997 engines. What can be done to prevent it? The last thing I want to do is go through the time, effort and money fix it only to have same reed block to crankshaft crash again.

You mentioned they need to be installed correctly...but there isn't much to it. The blocks just sit on the alignment (anti-rotation) pin and that is it...aside from applying correct torque and sequence when reinstalling the outer case.

What would make me feel better about it is having (perhaps) another pin or two in the reed block to help stabilize. I am having crazy thoughts about drilling through the front half of the case and into the reed block to add a second small pin and then sealing it up well from the outside of the case.

Any thoughts on this?

Thanks again!

 

[Faztbullet]

Re: Help - Magnum 40 Blown Reed Blocks

As Laddies said not a common problem but have seen it several times myself. Most of the one's I have seen, the engine has overheated and the plastic reed pins melted, which allowed reeds/reed stops to shift around. The 93-97 engines are a 3 cylinder and totally different problem and reed design. The pin numbers are 17-65855 which shows NLA but I have 5 left in a pack if you need them.

 

[riddert]

Re: Help - Magnum 40 Blown Reed Blocks

Thanks again for the responses...

My engines are 4cyl (longshaft) not 3cyl. Also, on my engines the pins are hardened steel - not plastic. The pin is still in perfect shape...the hole it fits into is not. No signs of overheating at all and both previous owners of each motor said the motors went down on startup immediately after changing water impellor. Pretty sure both engines were cold when the crash occured. Still thinking that maybe the crankshaft was displaced somehow when the driveshaft was installed. Maybe a couple of firm taps on the flywheel with a rubber mallet is all that would have been needed to prevent it? Maybe that would have helped seat the crankshaft-to-driveshaft coupling joint and insure crankshaft was not shifted up slightly...just guessing. I know the crank shouldn't be able to move much up and down, but maybe a couple thousands of an inch is all it takes?

Also, engine serial number is 0D011840 if that helps.

 

[Laddies]

Re: Help - Magnum 40 Blown Reed Blocks

When we built the 44 cu.in. powerheads for racing we loosen the crankshaft end play and open the reed stops to maximum, in stock classes we can not alter the thickness of the stops or blocke so it's common to have only .003 to .005 clearance of clearance from the crank to the reed stops so once in a while on a test wheel we will over rev a engine and catch a stop with a counterweight but that at way more RPM than your cranking a fishing engine. The second engine you said the hole was in #4 so thats not from pushing up, the only 2 fishing engines I have seen that in, one had a top main bearing out and the other had loose bolts on the bottom main cap letting the crank fall down.

 

[Faztbullet]

Re: Help - Magnum 40 Blown Reed Blocks

I am not talking about locating pin in block ,but pins that hold the reeds in place.

 

[Laddies]

Re: Help - Magnum 40 Blown Reed Blocks

Was in the library this evening and see that service bulletin 72-11 deals with engine problems caused by over greasing the drive shaft, by loading the bearings. Basically it says that on new installation never have more that 1/8 " of grease on the end of the shaft and in cases that the splines on both the crankshaft and drive shaft have not both been cleaned, only a light layer in the drive shaft splines. So I suppose that the damage could have been caused by over greasing.

 

[riddert]

Re: Help - Magnum 40 Blown Reed Blocks

Thanks for the input & help guys. Over greasing makes sense as well as some of the other items that were mentioned.

Now here is a question...would it be crazy to use one of the reed blocks from one engine for the other engine as is? Both have (1) good one. All else looks good - mains, rods, pistons etc...

 

[Laddies]

Re: Help - Magnum 40 Blown Reed Blocks

It won't hurt a thing as long as they fit tightly in the block, we always use a little master gasket of 518 for insurance on them, also inspect the labyrinth seal on the inside for wear or damage.