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Old 10-05-2022, 08:05 AM
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Originally Posted by Dragracer_Art
In latest news... I just dropped $2k on a closed cooling system. It's only a half system and doesn't touch the manifolds... but at least the engine wont have scummy water running through it and it wont freeze over the winter.

https://www.hardin-marine.com/p-1003...lf-system.aspx


Next will be a better set of manifolds with dry joints. Still shopping for the right system. Looking at Stainless Marine and Dana. Cannot swing $8k+ on CMI stuff. $3500 dry joint manifolds will suffice.
I never liked the VP and Mercruiser wet joints. Almost lost my last (merc) motor because of previous owners maintenance neglect. Had water in several cylinders one day after running on muffs in the driveway. Figured it out the next day when the motor was hydrolocked. Pulled all plugs, spun it over to push water out and fogged all cylinders. Resurfaced manifolds/risers and replaced gaskets and it was good as new. Motor wasnt hurt and still ran strong.
Dragracer,

To my knowledge, that's how all closed cooling systems work. The coolant runs through the engine while lake water runs through the heat exchanger and out through the manifolds/headers, cooling them in the process. Somebody correct me if I'm wrong....

Thanks. Brad.
(937)545-8991
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Old 10-05-2022, 08:10 AM
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Originally Posted by Brad Christy
Dragracer,

To my knowledge, that's how all closed cooling systems work. The coolant runs through the engine while lake water runs through the heat exchanger and out through the manifolds/headers, cooling them in the process. Somebody correct me if I'm wrong....

Thanks. Brad.
(937)545-8991
The full systems will also cool the manifolds, but still dump lake water out the risers/wet exhaust. I think the 1/2 system doesn't have enough heat exchanger to also cool the manifolds... but that's OK... im happy to put antifreeze in the engine and keep it sealed off.
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Old 10-05-2022, 08:12 AM
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Originally Posted by techman
I always thought side exhaust was a weird design. Is it done for packaging reasons? It certainly can't be for sound since you are hearing 4 out of sync cylinders on each side. It makes that V8 rumble sound like a UPS truck.
On the Chaparrals talked about here it is due to the hull/transom design. It was easier for them to route it out the side. I had a 266 Crownline that you could have it either way. I choose thru the transom on that boat. Sounds so much better.
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Old 10-05-2022, 08:13 AM
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Originally Posted by Brad Christy
Dragracer,

I also wonder about the 90DEG bends in the exhaust routing that is usually implemented with side exhaust. I would think they would induce backpressure that would be unwanted for a higher performance engine. We had them in our Rinker, and I often wondered if they weren't holding the engine back some.

Thanks. Brad.
(937)545-8991
Yeah... at 4" pipe ID i dont think it's an issue when the risers themselves are terribly restrictive.

I only ran 4" exhaust on my street legal drag cars and they were low 8-sec cars with nitrous and 1000+ hp.
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Old 10-05-2022, 08:15 AM
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Originally Posted by Knot 4 Me
On the Chaparrals talked about here it is due to the hull/transom design. It was easier for them to route it out the side. I had a 266 Crownline that you could have it either way. I choose thru the transom on that boat. Sounds so much better.
I agree with the better sound out the rear... and yeah... there is just no way to cleanly route pipes straight out the back of that style transom. There is nothing flat or square about it.
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Old 10-05-2022, 11:47 PM
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Stay away from huge cubic inches and monster torque, or you'll mangle your outdrive.
A 502/509 is a great combo because the large bore doesnt shroud the valves.
550 hp at 5600 is an easy target.
This is likely the upper limit for yoyr outdrive.

A 572 or 632 will make another 100+ ft*lbs of torque which will be tough for your outdrive to absorb. If you go that route, you will likely have real-world experience on exactly what the breaking point is for a DPX

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Old 10-06-2022, 05:04 AM
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Originally Posted by mcollinstn
Stay away from huge cubic inches and monster torque, or you'll mangle your outdrive.
A 502/509 is a great combo because the large bore doesnt shroud the valves.
550 hp at 5600 is an easy target.
This is likely the upper limit for yoyr outdrive.

A 572 or 632 will make another 100+ ft*lbs of torque which will be tough for your outdrive to absorb. If you go that route, you will likely have real-world experience on exactly what the breaking point is for a DPX

​​​​​​
The Raylar top end kit is 525+hp and maintains OEM-ish manners on the water. If I choose to go that route to start... it's right there with those HP numbers and keeps all the stock injection in place.
I think it makes 525hp on stock manifolds... so if I upgrade to decent manifolds too... I think he says 540hp+

Still lots to consider... and I appreciate everyone's input. I dont want to beat this topic to death so I will let the thread fall down the page unless folks want to keep bouncing ideas around.

Last edited by Dragracer_Art; 10-06-2022 at 05:07 AM.
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Old 10-06-2022, 05:07 AM
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I did finally get my GA registration and numbers yesterday... so the purchase from Illinois/LOTO is now sealed and complete. Seller did not have title in hand when we bought it (bank owned) so it's always a crapshoot how that kind of deal goes. I usually run from any deal like this (no title in hand) but the extra effort and patience was worth it. The boat is mint/garage kept and the sellers were top notch folks, so that went a long way with me.
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Old 10-06-2022, 05:16 AM
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Originally Posted by Cap'm Kurt
Techman and Icdedppl got it right.

Only thing is, is to check that your WOT rpm is near the top end of your recommended rpm for that motor. Otherwise it will feel more sluggish than it should. Very simple idea, but so many dont understand that concept, or have never even checked it. But chances are what you have is correct.
I just ordered some NMEA2000 stuff to connect my Garmin 73cv to the engine harness so I can see actual "real numbers". I don't trust dash gauges at all.
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