Thank you for that. I have been reading all the past threads about this engine and the KE exhaust I can. Yourself, SB, and Dean have all been supporters (along with a number of other members and other sites as well) of the Thunder n Lightning exhaust.

So this is where I'm at right now.

I have no exhaust. 180 hrs on engine. Valve springs have been replaced. Engine is already installed into the boat (cam swap is off the table for now)
Bravo 1 outdrive. All new maintenance parts replaced. (bellows, gimble bearing, U joints, reverse cable, seals, and fluid) Teague billet top cap installed. Simrek drive shower installed. Y pipe removed and block off plate installed

Here's what I have. 1998 Cobalt 252 bow rider 4,500 lbs dry weight Bravo 1 (1.50) had the 502 mag MPI turning Mirage plus 23P 5200 RPM at 63 MPH with 2 people on board and half tank of fuel. The boat will be used on Lake Erie, so 2-3' choppy conditions is normal. Bennett dual ram trim tabs have now been installed.

I opted to install the HP 500 because I want a little more speed. Not so much more that I need to install hydraulic steering or upgrade my out drive to something else. And the look of that blue engine under the hatch really looks great.

I've been doing a lot of reading of old threads and am kind of confused, so I am looking for some more input from you guys please.

I have the Hardin Seaward exhaust manifolds from my 502 mag already. All I would need is to purchase the HP 500 risers for $1400 and I can install that.
PROS: cheapest option, looks good
CONS: lose some of the HP I was hoping to gain from the engine swap

I have been researching the KE Thunder n Lightning. Lots of positive reviews
PROS: Tuned length exhaust with great HP output for NA engine. Reliable and durable
CONS: Cost nearly $4k Big, not easy to work on engine with them installed. Have read impeller failure (lack of cooling) can lead to catastrophic failure. Requires more $$ to make them look great

Also leaning towards the CMI Fusion headers.
PROS: Good performance. Look great. No need for tailpipes and clamps. Easy to work around installed on the engine.
CONS: Cost around $4k. Not many reviews as of this post. Are they prone to cracking/leaking?

I have sunk a fair amount of $$ into this exchange already, so I'm not looking to spend another $4k for just an exhaust. But at the same time, I want to gain the most MPH I can since I've spent so much already trying to achieve just that.

So is the little bit of HP being left on the table using the Hardin manifolds worth the extra $2500 cost?

Input please. Thank you

I have no real experience in this scenario but so far I’ve never heard of anyone regretting going with the KE setup.

Been running KE's exhaust since 95 on many motors, all over 750 hp, up to 1050. Not one failure. Have a dyno comparison on 1050 motor with KE pipe versus CMI big tube. Difference was like 15 hp. Now before switching to KE, I ran Stellings and CMI. No comparison in product issues. If you loose cooling and don't catch it, not good probably with any exhaust.

I understand KE TnL is a good exhaust. So you guys feel they are worth the extra $2300 over a set of Hardin manifolds?

Obviously I can sell the Hardin exhaust to re-coop some of the $$ spent. I've read some manifolds MAY give up as much as 40 HP compared to a header. Would that difference in HP be enough for you to pay the price difference?

I cannot talk specifically about the new Seaward system from Hardin. My expericane is Gil and Stainless Marine both performed exactly the same. I am sure Seaward will fall into the same category. You will gain hp and speed with the KE manifolds I am sure of that. How much? Probably around 1.5-2 mph. So is the gain worth the money to you? The CMI Fusion will be no better than what you currently have. It is just a short tube stainless manifold, it will not scavenge the exhaust any better than what you currently have on your boat. Does it look cooler? Yes. Perform better? NO.

If you are going to do the swap, stick with the KE. Anything else in your budget will be a lateral move.

That's exactly what I was thinking as far as gains. Thank you for that.

Decided to go with the TnL exhaust. Problem is, it's 1 month out before it arrives. 8(

Been a while since this has been posted, so in case you have never seen it (used to be posted alot)


https://cimg3.ibsrv.net/gimg/www.off...1ac70c5d9.jpeg

Here are better charts:
https://www.offshoreonly.com/forums/attachments/general-q/444097d1301322986-exhaust-dyno-charts-copy-exhaustdyno.pdf

Posted in this oso thread:
https://www.offshoreonly.com/forums/...no-charts.html

I have seen the first graph, but I've never seen the other charts. Thank you for that.

It's a double-edged sword. It shows how well the KE's perform, but at the same time only reinforces what I had thought earlier. A good set of manifolds is going to give up 15 - 25 HP to the KE's. But in reality that's just 1 - 1 1/2 MPH.

I can purchase just the HP 500 risers for $1400, or the whole KE exhaust for $3700. (sell off my exhaust and the total comes to around $2500)

So is the additional 1 - 1 1/2 MPH worth $1k? Dam.....