thru hub exhaust vs non thru hub

hi

i tried searching this topic but couldn't find any answers so if i am asking a redundent question someone please point me to the right thread.
i'm looking at buying a used 25-35hp outboard. in my price range $400-800 some have thru hub exhaust and some don't. how important is it? thru hubs appear to have a bigger prop but that could be deceiving because of the bigger hub. i can't tell but the amount of blade surface may not be that much differant. one dealer told me that the thru hub is more efficient because it gets the exhast away from the prop but then when you look at the commercial outboards they didn't have it for many years after thru hub came out. and i assume in a commercial application they wanted the most push for the hp.
so if anyone has any knowlede of the pros and cons of the two exhausts i would appreciate the input.
thanks

Re: thru hub exhaust vs non thru hub

I don't know the performance pros and cons but from my limited repair work on both I much prefer working on the standard hubs without thru exhaust but they are getting harder to find!

Re: thru hub exhaust vs non thru hub

thru hubs, are quieter, less exhaust noise. that was the reason for doing it. the water acts like a muffler. the exhaust and water have exited together since the 50's at least.

Re: thru hub exhaust vs non thru hub

As a general rule, the thru hub style has better gearcase design (speaking of the shape), and are therefor faster on the top end. And they can be run higher on the transom, giving even more speed advantage. Of course all rules are meant to be broken so all you guys with fast non-thruhub never mind calling me at 3:00 AM.

Re: thru hub exhaust vs non thru hub

hi
so how would a 25hp with through hub (and better designed gear case) compare to a 28hp SPl?(with the old non thru hub gear case) from what i have been told is that they are the same power head but the 28SPL has the old lower unit parts.

Re: thru hub exhaust vs non thru hub

The more modern 25 is usually smaller and more fuel efficient.

Re: thru hub exhaust vs non thru hub

not exactly sure what motors are in question. Year? If the powerheads are indeed the same, which remains to be seen, the thru-hub will outperform the old style.

Re: thru hub exhaust vs non thru hub

In terms of typical boating activities, the performance difference between the older style 25 hp motor with a pin drive prop, and the 28 hp SPL with through-the-hub exhaust will be negligible. What is likely to be more significant is availability of parts, inlcuding props.

I recommend that you surf the net a bit and talk to your local OMC/BRP dealer, to determine availablity for commonly ordered items such as the props, water pump components, etc. Bear in mind that while used parts will be available for each via EBay, Craigslist, etc., and can be just fine for replacing items that don't wear easily, in some cases they really don't last long or provide a reasonable solution to parts replacement needs. That being the case, new parts availability could be important.

I also recommend that you consider other issues such as motor weight, steering components and so forth. For example, I suspect that the 28 hp SPL is a heavier motor than the older 25hp, but the SPL may have a torque tube built into the transom bracket, while the older motor doesn't. These sorts of issues could end up being deciding factors because they affect things like how the boat will sit in the water, and how you will be able to set up whatever steering aystm you have in your boat.

As a die-hard OMC fan, however, I'm sure you'll like either motor as long as you pick one that is in good mechanical shape!

Re: thru hub exhaust vs non thru hub

hi
i was looking at a 1992 28SPL or a 1989 25 hp

Re: thru hub exhaust vs non thru hub

The thru hub exhaust helps to get the exhause out of the engine so has a little more power but it still what the HP says it is.

One disadvantage of thru hub exhaust is they do not back up as well unless it has some way to vent the eahaust above the prop. With thru hub exhaust the exhaust is right behind the prop so when you back up the prop is turning in exhaust gas not water. As you speed up in reverse you get even more exhaust gas. If motor vent exhaust at a different plac when in reverse then it will still back up good. The commerical motor used the old style exhaust so could get more reverse thrust.

Re: thru hub exhaust vs non thru hub

marquette said:

hi
i was looking at a 1992 28SPL or a 1989 25 hp

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Yep, they both appear to be de-tuned 35's. As far as the lower unit goes, in a flat-out race I would put my money on the thru-hub. In the pocketbook as far as repairs, propellers, etc., I would suggest the non-thru.

Actually, as somebody has already suggested, you should be happy with either one, assuming they are both in equal condition and have the features you want. But don't buy one hoping to add electric start or tiller handles, stuff like that.

Does anyone know anything about converting a through-hub exhaust system to a non-through hub system? I

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