Please look at this picture of this Lower Unit

[Jeb1971]

This blue lower unit came on an evinrude 200 I just aquired. I dont know the exact year. I am asking for help finding that out in another thread. I assume it is between 78 and 80. Look at what was done to this lower unit. Someone put bondo on the sides and sealed up the water inlets. They also attached this water piping on the side (just one side). Do you know what they were trying to do here? I have never seen anything like this.
The white unit is supposedly from a '79 evinrude 175. the bolt patterns are the same, but look at how much wider the blue case is than the white one. Is that just the difference between a 175 and 200 unit?
Thanks, John

 

[Dhadley]

Re: Please look at this picture of this Lower Unit

The blue one has a nose cone and low water pick up added. One for a Merc to boot. It still amazes me how many Merc nosecones we see on OMC's. The white one is stock.

Do both have fine threads for the prop nut?

 

[Jeb1971]

Re: Please look at this picture of this Lower Unit

Hello, Thank you for your reply.
Yes, both output shafts have fine thread.
What is the reason for this modification? I cant see where the water would go in, now that they filled in the inlets except through 2 small slots just below the cavitation plate, on each side.
Is this a desirable modification?
How is it better than stock?
Thank you.
John

 

[Dhadley]

Re: Please look at this picture of this Lower Unit

This is a performance mod. There should be several slots under the leading edge of the nosecone. The water goes in there, travels up the front of the nosecone and then over to the water chamber thru that hose. It's beyond me why people put a Merc kit on an OMC though.

As for the reasoning, originally we found out the the stock OMC gearcase like yours had a blow out speed in the low 70's. Not prop blow out in the traditional sense but gearcase blow out. There is a point that the vortex of air created by the blunt nose of the case reaches the prop & skeg. When that happens the prop grabs air and you lose steering. The boat takes a hard, sharp 90* left turn and there's nothing you can do except hang on and hope the boat doesn't barrel roll.

The fix was to make a sharper (sleeker) add-on nose. That fixed the blow out but the extra length created drag so the motors were raised higher to reduce drag. Then water pressure became an issue. So water inlets were added to the nose. Now you could run the gearcase high enough that the propshaft was even or above the keel.

Some flats fishermen use them to raise the motor to get in very shallow water. There are several styles for different purposes.

Do you need one? That's up to you. If your boat is a sub 60 mph rig it'll most likely slow you down. If you have a hydraulic jackplate and just need to get over shallow water without overheating, it may help.

 

[Jeb1971]

Re: Please look at this picture of this Lower Unit

Hi.

Thank you for your reply.
After dooing some degreasing, I did find the water inlet slots on the bottom of the nose cone, just as you described. This actually sounds like a pretty cool setup. I am lucky it came this way.

I am estimating to go over 70mph, so I supose I will use this unit because the barrel roll dosen't really appeal to me. LOL
Thank you for that valuable bit of information.

Is the keel the lowest part of the bottom of the boat? I have been running my motors where the cavitation plate is about 1" above the lowest bottom edge of the transom. I dont have a jack plate.

I will want to take your advice to position the motor as high as I can (propshaft even or above keel).

Thank you,
John

 

[Jeb1971]

Re: Please look at this picture of this Lower Unit

One more question and I kindly thank you for your time.

This modified lower unit has 2 slots (1 on each side) in the
exhaust housing section of the lower unit, very near the top and above the cavitation plate.
I haven't seen these slots in other lower units. Were they part of the mod and do they improve performance?

Thank you,
John

 

[Dhadley]

Re: Please look at this picture of this Lower Unit

Where the propshaft ends up will depend on what hull you have and what prop you use. As for the holes, they've opened up the exhaust. It's going to be fairly loud. It's just another performance mod. It may help, it may not. Again depending on what rpm you're going to run.

 

[Jeb1971]

Re: Please look at this picture of this Lower Unit

Great!
Thanks for all of your advice and help.

John