200hp carbs on 1989 150

[TownsendsFJR1300]

Further on the point on what engineers design, in the case of motorcycles the tricks of the trade are well known. Where horsepower restriction is required; we in Australia have large capacity bikes (600 - 700cc) that are restricted for beginner use; they use restrictions behind the carby, restrictions at the exhaust port, restrictions in the muffler opening, leaner mixtures, and particularly in fuel injection restrict how far the throttle can travel at the handle or at the throttle body. It was easy just to remove these to gain horses. .

Not in the US, but Europe, etc, there are HP restrictions on the same motorcycle engine (My Yamaha FZ6, 600cc-about 98HP, FI'ed).


The same engine, uses a different THROTTLE STOP on the throttle/butterfly shaft to STOP full opening and reduces HP to 78hp

[BQUICK]

if the exhaust tuner is a different part number it is different and the engineers made that change in design on purpose

I think it was more marketing...so they could offer 150 175 200. Also safety....if a boat is rated for 150 it needs to close to that for liability. They can't make it too easy to get 50 more hp.

I remember having a 68 Firebird 400 that throttle from factory only opened 2/3....30 seconds bending linkage yielded a bunch of previously missing ponies. I heard it was done on purpose by GM.

[TownsendsFJR1300]

I think it was more marketing...so they could offer 150 175 200. Also safety....if a boat is rated for 150 it needs to close to that for liability. They can't make it too easy to get 50 more hp.

I remember having a 68 Firebird 400 that throttle from factory only opened 2/3....30 seconds bending linkage yielded a bunch of previously missing ponies. I heard it was done on purpose by GM.

Do you remember if it had a Quadrajet carb on it?

[zenoahphobic]

I think it was more marketing...so they could offer 150 175 200. Also safety....if a boat is rated for 150 it needs to close to that for liability. They can't make it too easy to get 50 more hp.

I remember having a 68 Firebird 400 that throttle from factory only opened 2/3....30 seconds bending linkage yielded a bunch of previously missing ponies. I heard it was done on purpose by GM.

Yes,
Most of the motor world with wheels talks in terms of engine combustion chamber volume cubic capacity. But boats (and industrial engines) have a more specific need to disclose power output. Not only for the obvious safety in not overpowering a particular hull, but somewhat for the safety impact of the weight placed on the stern (weight tends to increase with increased power). Now of course hulls also specify weight capacity.

[BQUICK]

Yes....went from 14.8 to 14.40 on back to back runs. Actually bent the linkage in the staging lanes. Never got to thank the mystery man who told me about it at the track.

I think it had something to do with the hp limit in Camaros and Firebirds at the time. Corporate GM didn't want 396 and 400 motors in them and definitely not 427s and 428s.

[zenoahphobic]

Not in the US, but Europe, etc, there are HP restrictions on the same motorcycle engine (My Yamaha FZ6, 600cc-about 98HP, FI'ed).


The same engine, uses a different THROTTLE STOP on the throttle/butterfly shaft to STOP full opening and reduces HP to 78hp

My beginners XSR700 they did just that, and after market suppliers made a replacement plate to allow full opening. Interesting that the original on your example still provided that stop and they added one in front of it, as if you could remove the restricted stop without particular attention to precision.🤔

So in reality the premature stop equates to a smaller carby or throttle body without having to design and supply a different one. Of course the word throttle explains what is happening; we keep opening the throttle to increase power. By putting a larger carby or throttle body we are just opening that throttle further.

[BQUICK]

I guess at some point this spring I'll put the 200 carbs on and see what it yields. When I trim out the exhaust gets partially out of water so may that will help. I'm also thinking of pulling lower unit and comparing tuners and see if I can open the 150 one up some.

[BQUICK]

To add more to this....the 150 175 and 200 all use the same exhaust tuner/manifold. Only the PROV 150 is different and choked down looking. But appears to be a different shape as well.

Another thing I noticed was the 150 was rated at 5000rpm but the 175 and 200 are rated at 5500.

[zenoahphobic]

I didn't look into the individual details as I don't have easy access to drawings. I suspected the exhaust manifold might be the same (hence my argument about the exhaust above), because it would have required another intricate design and casting of a significant piece of metal. However I would not discount the possibility that some of the ports have been machined differently; I don't know whether there are different engine block part numbers that may reflect only port machining differences.
10% increase in rpm could give you 10% increase in ponies, that could be 15 ponies right there.

[Masonmobilemarine]

If you run these motors on dynos you'll see the motors are actually underrated.

We ran some dynos while I was in school. The 150's we're generally around 175 at Max hp. AND Max HP actually occurred around 4500 rpm or so.

Simply revving higher doesn't mean more HP.

Even with a different exhaust part number, id bet you'd pick up more HP if you threw 200 carbs on. I'd bet you would only notice it on a Dyno though.

Im one to believe that the exhaust isn't that important for making HP until you either start going very large in displacement or start using forced induction (turbo/supercharger).

I'd bet there's a different exhaust for fuel economy, not HP. I'd suspect you'd get more hp than your 150, but worse fuel economy than a regular 200.


Agree or disagree is fine.

[ausnoelm]

You saying the 150 was actually 175HP at 4,500RPM? you sure about that? and increasing RPM didn't increase HP?

[TownsendsFJR1300]

Max HP on the F150 is at 5,500 while WOT is maxed at 6,000:

[pstephens46]

Max HP on the F150 is at 5,500 while WOT is maxed at 6,000:

Think we are getting 2 strokes and 4 strokes confused. But.... Ain’t buying the 175 hp 150 deal.
Hell...maybe evinrude was involved.

[ausnoelm]

Even the Mercury guys wouldn't say a 150 was actually 175 HP at 4,500RPM, mind you, they do say every Mercury ever made is the most powerful motor in that range.

[zenoahphobic]

I wonder if the Dyno was on the drive shaft and not attached to the prop shaft, you'll get those figures.
Hard to make sense of the argument with a 4500 rpm max hp. for these motors. Torque maybe maxed at 4500 rpm?
Agree generally about the rest except at say 4500 rpm to quote your figure, that there will be no more hp by increasing revs, they are not that chocked I would not have thought.