Exhaust work on the tuner(megaphone) of v4 crossflows

[ssv170]

its all about the noise....

[keefallan]

Gordon, if you are interested here's what I did to my lower unit to help it out of the hole, and maybe a little more noise too



Yes, its all about the noise..........as long as you can back it up. There is nothing worse than being beaten by a dead quiet challenger and your just making noise as he waves passing you by.


I am optimistc to see whats on the inside now that I have seen Gordons photos. If not, (meaning exhaust is spraying down on the pump) I think I will weld an aluminum diverter plate above the water pump to protect it. Thoughts?

I obviously would have to keep an opening for the driveshaft.

Thanks for all the input gentlemen. Keep it coming.

[Gordon02]

I don't like the noise part of it, but I will agree that relieving the exhaust does improve holeshots. My little SS has one characteristic that no other outboard I've ever owned has "instant throttle response from idle". It has a huge 3" hole out the back of the short shaft. Mercury drilled holes in their factory hotrod, the 2.4L Bridgeports. I've copied that in my 2.0L fatblock project, but that's another color.....

I haven't started on the gearcase yet (waiting to complete the boat so I can bolt it up the paint is cured). I may do something like that too since I know it works on my black motor......Gordon

[ssv170]

just FYI the fastest tri hull this year ran stock exhaust and chopper prop, so much for noise....

[FMP]

Now they'll add the noise...

[keefallan]

just FYI the fastest tri hull this year ran stock exhaust and chopper prop, so much for noise....

I am sure thats true. But I dont think it was a v4 crossflow was it?

[keefallan]

I did get my 140 separated into pieces today. I had to sacrifice my upper mount to get it done. I drilled thru the upper mount where the bolts come thru from the steering head to drill out the bolts from the top. It saved my steering section and allowed me to save the v4 adapter as well. Using heat and some hammer raps, I was able to get every bolt out except for those two steering head to motor mount bolts.......worth it. The adapter is good, and tyhe mid itself is good.

Here's my thoughts on those steering head bolts..........after this last set(if anyone is interested). I tried everything on these to get them out. They are still seized in the steering head arm. I will get them out(by drilling if I have to), so I am not concerned. I have only been able to get the bolts out of a midsection 1 or 2 times out of a dozen teardowns that went into the midsection. Those bolts are accessible to water from the back side, as well as at the bolt head itself. So, unless there is a little slop in the holes' thru bore(where there are no threads) and anti seize is applied, you can count them good as stuck in these old crossflows. So, the way around it is to sacrifice the motor mount and just drill downward thru the aluminum and drill the bolt and sever it. It will still be stuck in the steering side, but you should be able to get it out(drilling being the last option).

Now back to the exhaust mod. I looked down thru the mid and wondered about cutting the megaphone on a slash cut with the long side of the slash blocking the exhaust's access to the water pump area. There is limited access to the water pump area, but I would still like to block it more or even direct away from that area and still have the megaphone open. A good or bad thought?

And I did look at the possibility of opening up the hole into the tuner. There's just not enough meat there to do anything wish. If I had a cnc machine, I would make a new megaphone that had some meat on it up atb the top and port the hole in the adapter , so it would move more air in volume at the bottle neck up top. I cant believe that there is not a breathing issue through that area.

And lastly, should I weld up the two holes in the in the sides of the tuner all the way up at the narrow area(like the v6's) or leave it alone?

[Gordon02]

Off track, but what year and is it a Johnson or Evinude? I just learned something new today - my Evinrude cover will not fit over my new BRP Evinrude replacement coils. Even when installed exactly to instructions supplied by BRP. The 1978 cover has a sharp slant along the rear top - so much so that even pointing forward on #1 and #2, the cover won't clear the #1 top coil. The solution is going to be using the large, aluminum "C" that came standard on the 1977 and earlier models. Luckily, my block has the 3 post that this C mounts to. The Evinrude cover is essential for me since I'm making a copy of the movie boat/motor.

I'm just curious to what coils you're going to use and how you'll mount. The old style coils are long gone and I wanted all-new coils and CDI boxes, so I had to resort to this mounting solution. A Johnson cover has much more room and has a much better breathing/venting system at the rear handle. I borrowed this one from the 1977 140 I just bought and did the trial fit you see here. I bought another C on ebay this morning which I'll bead-blast and paint to match the Evinrude colors. Gordon

[FMP]

Re slash ,
That would change the tuner signal, maybe distort the rarefaction and hinder scavenging. Makes me think about doing a curve to out the back of the leg , short inside curve end and longer outside both flush to an opening out the back of the mid . Still liking the original 77 with the idle back pressure reliefs welded shut if it has them. You have power trim for idling.

[Gordon02]

Keefallan, I think you're over thinking the tuner thing - John Tiger's article says simply to cut the tuner to 8" for a little extra at the top on light hulls. There is at least 12" between the end of cut tuner and the waterpump - that in addition to the fact they are not anywhere near alignment is enough for me not to give it anymore thought......

[powerabout]

I am sure thats true. But I dont think it was a v4 crossflow was it?

the class is v4 xflows

[Gordon02]

Powerabout, do you have links to some of these races? I haven't been to a boating race in many years. I'd love to see some of those V4's in action.

Thanks, Gordon

[FMP]

So what's the bore stroke on this looper?
https://m.youtube.com/watch?v=w_dkc-wHaiY
Not to go too far off topic for a minute

[powerabout]

Powerabout, do you have links to some of these races? I haven't been to a boating race in many years. I'd love to see some of those V4's in action.

Thanks, Gordon

https://www.youtube.com/watch?v=e3QrsmMCOG8
the racing is fantastic, I did notice the whole pit for all classes stop to watch which doesnt happen in any other class.

Having a new engine that must be relavant crap for racing is of course rubbish as this class demonstrates.

[Gordon02]

Thanks for the video. Lots of porpoising and lots of noise for what looks like mid 50's top speeds. Any idea what the speeds actually are and what weights these are running?

Gordon