Indmar Exhaust Manifolds/Risers

[robk]

I have a Carrera 20.5 Elite with a 496 (454 bored 0.060) that still has the stock Indmar manifolds and risers... In my quest for a little more horsepower for the upcoming summer I'm wondering if replacing these with an aftermarket set is a cost-effective way to gain a few more ponies?
Any recommendations or suggestions?
Rob

[jbone]

I've upgraded my Indmar 502 to the 502/502 and still have the Indmar manifolds. I have to wait on the headers. $$$ reasons.
I've been told they are not the worst factory manifolds, but headers will definately net good results.
I call to Lightning Headers could probably answer your questions.
Here's their link http://www.boatheaders.com/headers.htm
If you go with the headers, can you pm me with your results. I am very interested in real life info for these.
Thanks,
J

[BLOWN JOB]

they make two different kind one steel that are ok but the aluminum ones are better

[jetboatperformance]

Rob there are a multitude of options for your needs in both jacketed and cast ,most all will be a weight savings as well as a performance increase, alot may depend on cam and modification choices (now and future) Let me know if you need more info further Tom

[robk]

I've upgraded my Indmar 502 to the 502/502 and still have the Indmar manifolds. I have to wait on the headers. $$$ reasons.
I've been told they are not the worst factory manifolds, but headers will definately net good results.
I call to Lightning Headers could probably answer your questions.
Here's their link http://www.boatheaders.com/headers.htm
If you go with the headers, can you pm me with your results. I am very interested in real life info for these.
Thanks,
J
Thanks for the link, they have pretty awesome-looking stuff. Whichever way I decide to go; I'll give you my before and after #s.
Rob there are a multitude of options for your needs in both jacketed and cast ,most all will be a weight savings as well as a performance increase, alot may depend on cam and modification choices (now and future) Let me know if you need more info further Tom
The previous owner did a bunch of work to what used to be the 454 in the boat... now a 496, custom arias pistons, crane cam (don't have the part no here with me), and a bunch of other stuff. Just left the exhaust alone.
I don't plan on modifying the internals any further in the foreseeable future, so I was looking to the external stuff. I'll see if I can find the part number of the cam and post it tonight if that'll help.
Rob

[75MillerJet]

I thought the Indmar ex mans WERE considered aftermarket and flowed pretty good? In May 2006's issue of ***boat in the "454/502 Makeover" article (page 52 specifically) It shows a pic of a BBC with Indmar manifolds and it states that the BBC has been "transformed" with the available aftermarket products. :confused:

[robk]

I thought the Indmar ex mans WERE considered aftermarket and flowed pretty good? In May 2006's issue of ***boat in the "454/502 Makeover" article (page 52 specifically) It shows a pic of a BBC with Indmar manifolds and it states that the BBC has been "transformed" with the available aftermarket products. :confused:
Hmm.. that's a good point. I assumed they were "stock" since they came as part of the motor package (which has since been modified quite a bit). I'll have to see if I can find a copy of that issue; I would certainly like to read the article. Thanks for the tip.
Rob

[75MillerJet]

Hmm.. that's a good point. I assumed they were "stock" since they came as part of the motor package (which has since been modified quite a bit). I'll have to see if I can find a copy of that issue; I would certainly like to read the article. Thanks for the tip.
Rob
u can order back issues or i can scan the article on to my computer and get it over to u (if thats not illegal) :idea:

[SmokinLowriderSS]

Don't know about the Indmars, but my Niccson logs were replaced by Lightning headers last winter, 200 RPM gained against my Agressor B impeller, 50 HP, and that was on a stock (cammed and intake changed) 454. The base motor changes were the previous winter, only the headers changed that winter. I think they were well worth the $1200+ I paid USED (I got lucky).
Scanning and giving him the back-article should be no more illegal than mailing hin the magazine. Scanning it and SELLING it to him for, say, $1, would technically be piracy, since you are profiting from it.

[old rigger]

Hmm.. that's a good point. I assumed they were "stock" since they came as part of the motor package (which has since been modified quite a bit). I'll have to see if I can find a copy of that issue; I would certainly like to read the article. Thanks for the tip.
Rob
Rob,
You're correct, they're stock when you order an jet boat engine package from Indmar, and they're as good as it gets performance wise when compared to all other OEM (hardin, harman, glenwood and so on) aftermarket aluminum manifolds until you step up to headers. There was also a comparison done years ago in one of the boat mags that proved this. :)

[robk]

Rob,
You're correct, they're stock when you order an jet boat engine package from Indmar, and they're as good as it gets performance wise when compared to all other OEM (hardin, harman, glenwood and so on) aftermarket aluminum manifolds until you step up to headers. There was also a comparison done years ago in one of the boat mags that proved this. :)
Ah, thanks Rich, now it'll be even easier to decide! :)
So if these are considered the "best" stockers, is it worth the cost to go to headers? Am I going to get nailed with a noise ticket 30 sec after leaving the no wake zone?
Thanks again everyone for your responses!
Rob

[old rigger]

I took the wet headers off my dads ol jet and put on a set of Indmars (my idea, not my dad's, we had just had our son and my wife was freaked that he might somehow fall into the headers and be scared for life. Hell, I fell into them and others a bunch of times and those blisters don't hurt all that much) and we went from pulling 5400 to 5300. 'Course the engine wasn't much compared to what most of you guys run today, it'd show 72-3 on the speedo, this was 20 years ago...that's all we had to go by, so it really wasn't any big deal to step down to the Indmars. It was a '21 family open bow anyway. ;)

[robk]

I took the wet headers off my dads ol jet and put on a set of Indmars (my idea, not my dad's, we had just had our son and my wife was freaked that he might somehow fall into the headers and be scared for life. Hell, I fell into them and others a bunch of times and those blisters don't hurt all that much) and we went from pulling 5400 to 5300. 'Course the engine wasn't much compared to what most of you guys run today, it'd show 72-3 on the speedo, this was 20 years ago...that's all we had to go by, so it really wasn't any big deal to step down to the Indmars. It was a '21 family open bow anyway. ;)
Old Rigger always has the best stories....
Well considering the cost of headers I'll probably stick with the Indmar "stockers" unless I can find something showing some good horsepower gains with headers. Its probably fast enough as it is, being a '21 family open bow :D

[OKIE-JET]

Hey guys...just scannin for info in here and had a ??..I have the aluminum indmars in my open bow family truckster as well...but im havin a problem with a leak at the point of riser and man. assembly. Would it be o.k. to take the two apart and throw on a lathe and remove .005-.010 to tru up both pieces. Also, each are assembled with one gasket on either side of a .030 stainless spacer, the gaskets have the holes around the perimiter and match up with the riser and man, but the stainless spacer does not. Why is this?

[probablecause]

I have a Carrera 20.5 Elite with a 496 (454 bored 0.060) that still has the stock Indmar manifolds and risers... In my quest for a little more horsepower for the upcoming summer I'm wondering if replacing these with an aftermarket set is a cost-effective way to gain a few more ponies?
Any recommendations or suggestions?
Rob
You are running a low to medium compression N/A motor (ie. not using AV gas or race fuel), you won't notice much of a diffrence for the money you are going to spend. Now if you had the snail logs and were going to upgrade, I would say that would be a different story.

[robk]

You are running a low to medium compression N/A motor (ie. not using AV gas or race fuel), you won't notice much of a diffrence for the money you are going to spend. Now if you had the snail logs and were going to upgrade, I would say that would be a different story.
Actually the previous owner stressed to me that the builder recommended running no less than 100 octane due to the increased compression of this motor.... The build sheet shows right around 170 PSI per cyl... Hope I haven't been taking a bath on race fuel.
Rob

[SmokinLowriderSS]

Hey guys...just scannin for info in here and had a ??..I have the aluminum indmars in my open bow family truckster as well...but im havin a problem with a leak at the point of riser and man. assembly. Would it be o.k. to take the two apart and throw on a lathe and remove .005-.010 to tru up both pieces. ?
Sure, IF you can get them apart w/o destroying the logs. Mine corroded thru internally (and externally) so donated my logs to the local HS for aluminum. Took my snails to Duane in case he can sell them. destroyed the logs trying to get the snails broken loose from them. No dmage to the snails tho at that heavy gasket surface.
Also, each are assembled with one gasket on either side of a .030 stainless spacer, the gaskets have the holes around the perimiter and match up with the riser and man, but the stainless spacer does not. Why is this?
The gaskets are the same. The spacer does not need holes as there are no holes in the snail-flange. Whoever put the spacer in just used 2 sets of log gaskets. I gues the log gaskets wouldn't require holes either, but that would put a bunch of gasket material in the water stream area, which would only eventually come loose and become a problem someplace.

[OKIE-JET]

Thanks for answering smokin, but the indmars I have are not logs, they are top exit with a riser, four bolts around edges. I have removed them and replaced gaskets but still pinhole leak in one, same place as before, was thinkin of trueing them on a lathe. Its strange that my risers have the same matching holes as the manifold and the spacer does not, but it looked factory to me??

[probablecause]

Actually the previous owner stressed to me that the builder recommended running no less than 100 octane due to the increased compression of this motor.... The build sheet shows right around 170 PSI per cyl... Hope I haven't been taking a bath on race fuel.
Rob
Rob, find out who the builder was, if you can. Otherwise, start backing off of the octane until you get some good pings - just kidding.
PS Great Boat!

[4trax]

Thanks for answering smokin, but the indmars I have are not logs, they are top exit with a riser, four bolts around edges. I have removed them and replaced gaskets but still pinhole leak in one, same place as before, was thinkin of trueing them on a lathe. Its strange that my risers have the same matching holes as the manifold and the spacer does not, but it looked factory to me??
Doe your exhaust and plumbing look like this?
http://i144.photobucket.com/albums/r162/4trax67/Boat%20parts/79P1010221-med.jpg?t=1168502042
If it does then it's correct and plate is in there stop the water flow for a different way of plumbing. If you want to preheat water before it goes into block then leave those plates with no hole in there. This is what I'm switching over to now. My is plumbed to where the water is not being preheated . Not good for block and inside components.

[75MillerJet]

Doe your exhaust and plumbing look like this?
http://i144.photobucket.com/albums/r162/4trax67/Boat%20parts/79P1010221-med.jpg?t=1168502042
If it does then it's correct and plate is in there stop the water flow for a different way of plumbing. If you want to preheat water before it goes into block then leave those plates with no hole in there. This is what I'm switching over to now. My is plumbed to where the water is not being preheated . Not good for block and inside components.
hey, thats a pic of my boat when it was owned by Jetdriver

[jbone]

That water line looks like it is going into the valve cover ventilation filter.
Thats funny.
J

[OKIE-JET]

Doe your exhaust and plumbing look like this?
http://i144.photobucket.com/albums/r162/4trax67/Boat%20parts/79P1010221-med.jpg?t=1168502042
plumbed just like that. Thanks.

[4trax]

plumbed just like that. Thanks.
Then from what I've been told that is the correct way to do it. You want to preheat for the block so you don't give it thermal shock. Wears out pistons and rings and other things prematurely.:D

[robk]

Hey guys...just scannin for info in here and had a ??..I have the aluminum indmars in my open bow family truckster as well...but im havin a problem with a leak at the point of riser and man. assembly. Would it be o.k. to take the two apart and throw on a lathe and remove .005-.010 to tru up both pieces. Also, each are assembled with one gasket on either side of a .030 stainless spacer, the gaskets have the holes around the perimiter and match up with the riser and man, but the stainless spacer does not. Why is this?
I've the same problem with mine leaking in that area as well -- there has to be a better way to seal those up. I'm going to take a guess and say that the exhaust leaking into a closed engine compartment can't be helping performance any.
Did you ever take yours apart and clean up the mating surfaces? If so, what results did you get?
Rob

[ck7684]

Personally, I think going to jacketed headers is a bit expensive...I have all the performance I need with my Indmar logs and snails. If I encounter problems in the future with these, I may upgrade to headers, but until them I'll save my pennies...BTW I'm pulling 5300 RPM on a fresh pump and "A" Impeller

[gr16241]

I firmly believe Lightning jacketed headers are well worth their price. I saw an increase of 400 rpms simply by changing to these headers. I have heard of increases between 200 and 600 rpms depending on how much horsepower the motor has. They sound awesome also. Watch these posts - you can pick them up used for about $800 - $1000. If you can swing to money don't hesitate to change over. As for heat, I think the headers are cooler to the touch than my logs were.

[smiggley]

Im in kinda the same situation.... Im running a basically stock 454. Running 850 Holley 4165 with Hardin logs, and Mallory dual point. First year that I owned it I did nothing to the boat. It topped out @4300rpm. 56mph. Last winter added a Pertronix unit. Adding a midrise dual plane Edelbrock mani, and Place diverter. That bumped it up to 4700rpm and GPSd at 63. I picked up a set of aluminum Indmars with 4"tips.
My problem is if I want to run the Inmars, I have to cut larger holes in the transom and remake my engine cover. Nothing too bad to, but if Im not going to pick up any decent gains from it, Id rather just leave it alone. Its a pretty unmolested Miller.
The other factor is futures plans of larger engine and being able to use the Indmars for that.

[ck7684]

Thats another issue I have, is fitting headers underneath my stock engine cover. As is, I'm going to need to raise it up some unless I want to run one of those very low arrestors. I would also have to cut larger holes in the transom, but I really dont see that as a problem. Just make sure the headers are going to line up properly with the holes...
However, in my case I already have as much power and speed as I feel is safe for this hull, so I'm really not looking for any more from my setup. I am making quite a bit of power and still using logs though...

[smiggley]

Personally if I am going to run a cover. It better look like its not a giant lego block sitting in the back of the boat. If all thats going to hit is the arrestor then I would go for a low profile arrestor. Thats what I am currently running and I have tried running the engine with the cover off and no arrestor and also with a taller arrestor and I saw no gains or losses. None that I felt at least.
I chose Indmars because they looked liked the lowest profile exhaust, plus I got a pretty good deal on em.
Good deal or not, Im just wondering if the gains are worth the effort. I heard that there was an issue of ***boat that showed exhaust gains and arrestor gains mixing and matching different parts. Any have this that they can scan or see what the gains were? Thanks

[Outlaw]

I have the article I will scan it

[ck7684]

I only need to raise my cover up a small amount. I believe in having plenty of space for incoming air, even if an arrestor doesnt restrict much. There are definately gains to be had with headers, its just that they are so damn expensive IMO, unless you go with OT's...
If I ever do upgrade to headers, the cover is staying off and I will just add some kind or surround trim around the engine...