Inline exhaust mods?

[zmoz]

Wanting more and more to go out and burn some gas everyday...I don't know how I'm going to make it until june. :rolleyes: I NEED to go work on my boat...are there any exhuast modifications I can do to my inline 6? Not for performance, necessarily, but sound? I like 'em loud...;)

[Raceman]

http://forums.screamandfly.com/forums/showthread.php?s=&threadid=47326

[carmex234]

I run a 16' Tidecraft weighs about 675 with a full tank of gas. It came with a 90hp nissan, great motors,had it since 92 and its now on its last bore so i opted to repower. Found a 115 inline the guy wanted $400 bucks, i did a leakdown and no more than 10% leaked past on all 6. Its a tight running motor, a pain in the butt to time/synch the carbs but once set. I also added a manual jackplate and hot foot with trim on the wheel. What is the gear ratio? i can spin the hell out of a 21p ss, so i have a 23p aluminum on the way. Overall im happy, im no stranger to fast bass boats but i dont think my hull is right for moving up to a 150 inline swap,that is what i call SCARY FAST!! I need a GPS,how fast do you think this setup is with 115 and 23p? 55-60mph? Once i do the water psi install im going to start raising the motor on the plate. What does the motor height affect besdies drag and RPM/speed? Too high and holeshot suffers? Prop cavitates?

In 3 weeks im getting my 1st pure speed boat, found the love of my life a hydrostream V-king 81' great shape,new transom and a v-6 150. guy wants 3K. Does that sound kinda high to anyone else? He just rebuilt the powerhead,but the boat needs a set of cool chairs,and a bench or something for the back. Drove it out on canyon lake here in texas and its a screamer. Many improvments are planned, move the steering to the center of the boat,solid motor mounts and a jackplate. i ran it with a 30p chopper and it had almost too much bowlift(i have heard these boats can flip over). So a kill switch is also a must, the old man that owns it didnt think he needed one, also going to hydraulic steering and center all the weight (seats,gas tank,battery)right down the centerline of the hull. Hopefully this will reduce if not eliminate the chinewalking, i had a hard time at first it walked so bad,and any trim input up or down only makes it worse. Its friday,and yes im just killing time till5pm:)))

[Raceman]

Your 115 most likely has a 2:1 gear ratio, although they were 1.78:1 in 70, 71, & 72. The old 1150's weren't exactly high RPM motors and you'll find the torque curve falls off substantially past mid 5's.

"What does the motor height affect besides drag and RPM/speed? Too high and holeshot suffers? Prop cavitates?"

That pretty well covers it, except in some applications you'll lose bow lift as you increase transom height. It just depends on the dynamics of the boat.

[carmex234]

Right now its set with the motor clamp just about level with the transom,and no rooster tail, so im sure i can raise 1-1.5'' just watch the pressure. How fast do you think this rig runs? Do you know if tidecraft hulls are the same mold as a laser?

[QUICKSILVER]

If you don't want to drill holes in your old inline and ruin the antique value of your engine, since the mods don't actually increase HP or speed, you could invest in a nice stereo sound system, with a huge amp. Then you could bungie cord a Mr. microphone, from Ronco, to the midsection. When you want to be loud, just turn on the Mr. microphone and let her blast. When the water cops are around, turn the volume off, and stay out of trouble. You can also get a 100MPH speedometer and do a little tweaking so that it reads around 80 when you are only doing around 35. That will impress your buddies. These cheap mods work well, and you still have a nice stereo system to listen to. You can always remove the stereo and install it in a new boat when the time comes.

[sho305]

I was going to do that, but I thought the Ronco was not waterproof...:D 18" subs....

I think the good way is to drill the sides of the exhaust cavity in the top of the LU? You can thread for plugs. Some say the mid will crack if you drill that.

My '73 1500 runs a 20ss Laser at 6k, that is like 50-54 on the prop calc. 17' vee open bow heavy Checkmate.

[gaineso]

My '86 Inline 115 pushes my Glasstream 15V (about 900 lbs dry) to 59.6 on GPS with a Turbo II 22" at 6,000 RPM. Gonna try a Lasert II or Raker to see if I can get a little more bow lift and will get over 60 GPS. And that's with 18 gals gas, two batteries, full fishin' load and 210 lbs behind the wheel.

[sho305]

My laser, I sharpened it up some is all. Some here say they need to be worked to really perform. I know one thing, it has loads of bow lift. I can trim it out of the water and still have lift. It loses water pressure and still carries the bow. It is raised 2" on the transom, so that is pretty big trim angle on it. Flat I think the cav plate is about 1" above the bottom. I have not tried other props recommended here for that kind of hull though so I can't compare.