Offshoreonly.com - LS Build: In Progress

Offshoreonly.com (https://www.offshoreonly.com/forums/)

- General Q & A (https://www.offshoreonly.com/forums/general-q-20/)

- - LS Build: In Progress (https://www.offshoreonly.com/forums/general-q/358652-ls-build-progress.html)

Quote:

Originally Posted by mggdoors (Post 4670156)

A turbo LS jetboat would be awesome. And easy to do with open engine bay.

Yes, and no need for a $$$$ front drive setup, no water pump, p/s, etc needed, just a alt mount..simple, thinking about twin turbo deal, as can get most of those parts for the cost of the marine exhaust.

Quote:

Originally Posted by Wildman_grafix (Post 4670188)

Are those SS?

yes these are stainless. I had cmi do them in black as i liked the way that the new 860 headers looked in black.. I dont believe cmi will build anything in mild steel...

This will be my 4th season running a 408ci LS in my Checkmate and I love it. The sound is amazing and what surprised me the most was how much the handling of the boat improved over the big block, especially in rough water. To me, this is how the boat should have come from the factory. I'm still playing with my set up prop wise, but so far I have seen a best of 75.9mph. That's only turning 5700rpms. I have a few props to play with this year to try to get those revs up. I will say this, after 3 years I'm getting bored, so the next thing is going to be some kind of boost.

One thing I haven't heard anyone mention on here yet, especially with your cam choices, is reversion. The LS is a water sucking M.F.er!!!! I fought it for months with mine. I'm running lightning headers and started out with just extended collectors. That sucked so much water that it milkshaked the oil in less than 5 minutes of idle time, on the hose. So then I had the headers made dry to the tip. The water came into the exhaust stream in the last 1/4" of the tailpipe and it still sucked it in like crazy. I ended up having to make the exhaust completely dry (still jacketed, just no water in the exhaust stream). While it sounds awesome, the noise can get annoying (98dB at idle in the cockpit) through long no wake zones. So when you guys do your initial fire ups, keep a close eye on the tips.

Quote:

Originally Posted by corey331 (Post 4670289)

What are your cam specs? You will notice I setup my cam with antireversion in mind. I do have 8 degrees of overlap at .050 and [email protected] but to combat reversion I have the evc at -.5 which does not allow the down stroke to draw back on the exhaust. Also going to be running the tall hp500 tails modified with 60 degree downturn where water dumps over the edge of a cliff. Post your specs. Info for future guys to build upon. Thanks for the post

Quote:

Originally Posted by corey331 (Post 4670289)

One thing I haven't heard anyone mention on here yet, especially with your cam choices, is reversion. The LS is a water sucking M.F.er!!!! I fought it for months with mine. I'm running lightning headers and started out with just extended collectors. That sucked so much water that it milkshaked the oil in less than 5 minutes of idle time, on the hose. So then I had the headers made dry to the tip. The water came into the exhaust stream in the last 1/4" of the tailpipe and it still sucked it in like crazy. I ended up having to make the exhaust completely dry (still jacketed, just no water in the exhaust stream). While it sounds awesome, the noise can get annoying (98dB at idle in the cockpit) through long no wake zones. So when you guys do your initial fire ups, keep a close eye on the tips.

Mine haven't made it into the boat yet, but the builder put 40 hours on them with full dry exhaust. Does anyone make anything to muffle dry exhaust? Inserts?

Quote:

Originally Posted by 242LS (Post 4670299)

Mine haven't made it into the boat yet, but the builder put 40 hours on them with full dry exhaust. Does anyone make anything to muffle dry exhaust? Inserts?

I onow dennis said he did have some reversion initially with those but corrected it. I have ran ggb mufflers on gil dry exhaust. Helped alot. I ran 5 rings. Idle before mufflers was 119db after 107db. You can buy tgem with more as well. He also makes an external clampon that works well too. Hope this helps.

Quote:

Originally Posted by mggdoors (Post 4670292)

Here is my cam card. While it is pretty aggressive, I have known quite a few others who have had issues with a less aggressive cam.

https://cimg2.ibsrv.net/gimg/www.off...5be6ca62ac.jpg

Quote:

Originally Posted by 242LS (Post 4670299)

Mine haven't made it into the boat yet, but the builder put 40 hours on them with full dry exhaust. Does anyone make anything to muffle dry exhaust? Inserts?

I built a set of clamp on mufflers for mine using GGB mufflers. I used the 3 ring sport mufflers and it made a heckuva difference. I can post videos of the differences later when I'm not at work (government computer). I always use the mufflers when I have my 6 year old twin girls on the boat with me, but pull them when it's just the wife and I.

I am using the imco base plates and welding them to a set of these tails but customized on the back turn. With the marine power/ imco (same) manifoldhttps://cimg8.ibsrv.net/gimg/www.off...a0b17d36eb.png https://cimg9.ibsrv.net/gimg/www.off...034d3e0f0c.png

Quote:

Originally Posted by corey331 (Post 4670308)

Here is my cam card. While it is pretty aggressive, I have known quite a few others who have had issues with a less aggressive cam.

https://cimg2.ibsrv.net/gimg/www.off...5be6ca62ac.jpg

Good power cam. See how the int/ex split forces the exhaust closing past 0 (8in your case). I can see why you had to go dry. Good for scavenging. Bad for reversion. I opted the other way to keep the db down and headers are not in the budget. Yet........... lol. Any dyno numbers??