What is the difference tru-hub prop and non-thurhub prop

[jcsercsa]

HI all, I have a 1962 1000 100hp merc and I do know that the water has a out let on the small fin and not threw the prop, what i am wondering is it just the hub that is different and can I change a truhub prop to a nontruhub prop???????? And everone have a happy new year !!!!! Thanks John

 

[oops!]

Re: What is the difference tru-hull prop and non-thurhull prop

Re: What is the difference tru-hull prop and non-thurhull prop

props arent my stuff.....

HAH....(what is?)

but i dont understand the question.
it may be just me.....

 

[Silvertip]

Re: What is the difference tru-hub prop and non-thurhub prop

Through-hub refers to the path the exhaust takes to get out of the engine. On a through-hub engine the exhaust passes out of the engine through the hub of the prop. On a non-through hub engine it passes out a separate opening. If you put a non-through hub prop (if it were possible) on a through-hub engine, the exhaust would have a tough time getting out of the engine.

 

[jcsercsa]

Re: What is the difference tru-hub prop and non-thurhub prop

Yea but I have a non-thruhub, can I use a thruhub,and can I switch the hub or are they perament?? Thanks John

 

[Texasmark]

Re: What is the difference tru-hub prop and non-thurhub prop

Years ago Merc realized that if you put the exhaust in the center of the propeller "propwash" the wash will carry it well behind the boat and it will run quiter....yeah, a quiet tower of power.......Ha, Ha. They also realized, as did others, that rather than a conical cap on the end of the propshaft to reduce drag, you can pump the void behind the propshaft full of exhaust gasses and reduce/eliminate it.

In comes the thru hub exhaust.....mid '60's as I recall. and out goes the popular (everybody did it that way back then) exhaust tube at the rear of the antivent plate....................till Brunswick purchases Chrysler...ala Force.

Next thing you see is the Force still exhausts out the back of the antivent plate, but they have (what looks to be) a standard Merc "thru hub" prop on it. Well, what happens to drag when you have this empty, squared off, tube at the center of the propwash. Well, it mustn't be good for performance or over the years, all the designers that made streamlined gearboxes were just nuts! I seriously doubt that.

I never saw data on the Force lower unit before and after they went with the actual thru hub exhaust. A comparison would be interesting.

I had the Chrysler 85, before the Brunswick takeover, and it had a very long, definite cone on the tail end of the prop shaft.....nice and aerodynamic.

More of my 2c's.

Mark

 

[Silvertip]

Re: What is the difference tru-hub prop and non-thurhub prop

Just because a prop fits the splines on the prop shaft does not mean it will work. Diameter of the hub on a prop is designed to match the diameter of the lower unit housing. If the prop fits the shaft you can certainly try it but I doubt it will be a very efficient set up. As for switching the hub, that depends on what you have to deal with. If the prop is an Interchangeable Hub System where the drive pieces are separate, you buy the hub that fits your engine. You can then install any prop with the IHS system from any manufacturer. If the hub is pressed into the prop you would need to have a prop shop press out the old hub and replace it with one that matches your engine. But if that's the case, why not just buy the proper prop to start with and know it will work.

 

[Bondo]

Re: What is the difference tru-hub prop and non-thurhub prop

Yea but I have a non-thruhub, can I use a thruhub, Thanks John

Ayuh,........ In a Word,................. No.......

You Need a Prop that Fits your motor..................

If you were to put a Thru-hub Prop on your 100hp motor,........
You might be able to utilize 10hp of what's available..........
In other words,......
You'd be Better off Rowing.................

 

[jcsercsa]

Re: What is the difference tru-hub prop and non-thurhub prop

Its just I seen a prop, on ebay that was the right size 13,3/8 is the max I can put on her, So i thought I would ask before I bid!! So I will take it as a no!!! Thanks guys !!!! John

 

[jimmbo]

Re: What is the difference tru-hub prop and non-thurhub prop

1962 was the fisrt year Mercury marketed a 100 hp. From day one it has had a Thru hub exhaust.



Tex... About the Farce engines with the merc props... There were some versions where the exhaust exited thru both the exhaust snout and the prop hub.

 

[jcsercsa]

Re: What is the difference tru-hub prop and non-thurhub prop

Jimbo i must have one of them but i could swear it was exhaust snout just above the prop, !!! so does that mean that mine is a tru-hub ?????????? JOhn

 

[pduquette]

Re: What is the difference tru-hub prop and non-thurhub prop

Jcsercsa ,I'm a J/E guy so I won't pretend to know much ....The best I can give is for you to know you're shaft.....propshaft that is . Length, diameter,number of splines,threadpitch,thickness of the spacers/washers,etc.
the more you know the easier it will be to find a match . I keep alot with me in my motor manual to help id stuff at swapmeets,yardsales,dumped at the side of the road etc. Another angle would be to get friendly with a local merc guru - NOT the guys with the shiny new storefront and ton of new motors to sell..... there's usualy one nearby you can real talk to with out getting shoved out the door "for wasting their time"

 

[jcsercsa]

Re: What is the difference tru-hub prop and non-thurhub prop

Thanks all, I have to get the manual !!! just thought someone might know !!! thanks all John

 

[Texasmark]

Re: What is the difference tru-hub prop and non-thurhub prop

If that's all you want to know, take the prop off and look. If you see hollow chambers in front of it and there is some exhaust carbon in there and on the inside of the prop hub, then obviously it is. If not, it's not. Now whether you have an engine that exhausts both places, I have no Idea. If there is such a critter, maybe it was used during the transition from snauze to thru hub on the Force.

Mark

 

[Frank Acampora]

Re: What is the difference tru-hub prop and non-thurhub prop

Just to clarify the Force issue: In the '90s, Force made a dual exhaust lower unit which exhausted gases through both the prop hub and the exhaust snout. It was relatively uncommon. They only used it on a few models of the larger engines--85 hp and up. They used the same thru-hub prop (piece of crap in my opinion) on all gearcases whether they were dual exhaust or not, and eliminated the tailcone and black plastic flare ("anti cavitation") washer.

Don't know why they did it as there was no measurable difference in performance. I do suspect that they kept the exhaust snout out of convenience: less redesign of the lower unit case and snout still functions as a trim tab. And, of course, better advertising--dual exhaust MUST be better and more powerful than single, right?

As a consequence of the design, they needed to move the water pick-up holes from the rear of the gearcase torpedo to a vertical line on the leg of the lower unit---thus resulting in a much higher water pick-up location. Net effect was that if someone wanted to use a jackplate and run the engine high, reliable water pick-up to the pump was suspect.

 

[jcsercsa]

Re: What is the difference tru-hub prop and non-thurhub prop

Why thanks Texasmark I would have never thought of that!!!!!! but seeing its 27 degrees out there today and yesterday with a high of 7 , well thought it would be a little bit easier to find out here !!!!! Thanks frank that does sound better dual exhuast !!! that was in the 90s , you dont know about the merc in the 60s ??? I was wondering about the pick ups with it being on the small fin????