Indmar 5.7 310 HP, What is the best carb to run on the set up.

hall832

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Running twin Indmar 350's with timing at 10 @ 1000 rpm's and -32 advanced. the Holley's that came with the new motors don't seem to be a good fit. has anyone else changed out the carbs and if so to what.
 

Bondo

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Re: Indmar 5.7 310 HP, What is the best carb to run on the set up.

Running twin Indmar 350's with timing at 10 @ 1000 rpm's and -32 advanced. the Holley's that came with the new motors don't seem to be a good fit. has anyone else changed out the carbs and if so to what.

Ayuh,.... How so,..??
 

hall832

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Re: Indmar 5.7 310 HP, What is the best carb to run on the set up.

I am having trouble with the vacuum secondary, I think a mechanical secondary would be a better fit. The Indmar Holley's air fuel adjustment is blocked off.
 

Scott Danforth

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Re: Indmar 5.7 310 HP, What is the best carb to run on the set up.

a mechanical secondary is not needed.

what kind of problems are you having with the vacuum secondary?
 

hall832

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Re: Indmar 5.7 310 HP, What is the best carb to run on the set up.

secondary not opening.
 
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Scott Danforth

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Re: Indmar 5.7 310 HP, What is the best carb to run on the set up.

then your not loading the motor enough. that is the beauty of a vacuum secondary. unless you need the extra air flow, it wont open. I can actually hear when my secondaries open on my holley, and it is only above 4200 RPM and under WOT.
 
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Re: Indmar 5.7 310 HP, What is the best carb to run on the set up.

Its pretty easy to set up a holley.
Get a secondary vacuum canister spring kit, it comes with 3 or 5 springs. Dont really remember.
Hook up a vacuum gauge and see how much vacuum you pull at wot. Then you can find a spring that will suit your engine.
You might have to play with it a bit but its pretty easy to get it right
 

Scott Danforth

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Re: Indmar 5.7 310 HP, What is the best carb to run on the set up.

if the holleys came from Indmar, I am certain they are set up right to begin width. I have been to Indmar and the guys there would not put out a motor without it being set up right from the onset.
 

hall832

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Scott and Rodrigo
thanks for you answers. Rebuilt the carbs top to bottom. Running under a load WOT 2900-3000 rmp's secondaries will not open. If i manually push the vacuum pump shaft up the secondaries the motor jumps up in rpms. I have completely gone through these carbs. Vacuum pump, bowls, pressure valve. not sure what to check next. I don't want to go to Double Pumpers. i want these to work how Indmar set them up.
 

Scott Danforth

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prior to jumping into the carbs, you did mention that these were new motors. if that is the case, I would have indmar deal with it. that is why people buy new - for warranty.

however if that bridge has been crossed, have you done the paper clip trick to verify the secondaries are not moving? again, if you are not loaded enough, they wont open.

which carb? 4150 or 4160? which power valve is your carb set up with? what is your jetting, and which spring do you have in the secondary actuator?
did you replace the cork gasket between the vac actuator and the carb body?

Here are a few other bits of information that may help.

https://www.youtube.com/watch?v=4xOiJQj6CSU

Holley Performance Products provides award-winning technical support via phone Monday through Friday from 8AM to 6PM CST, and Saturday from 9AM to 3PM CST @ 270 781-9741
 

hall832

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Crossed the Indmar bridge. I stand corrected on the age of the motors. A couple years old. 1.4160 2.power valve 2.5 3. White spring 4. Not sure on jetting. I got the build info from Holley. Just don't have it here.. 5 I did replace the gasket. Holley has been trying to help.
 

Walt T

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A mechanical secondary carb setup is a waste of money for your motors. Do the math, your motors don't need the secondaries. If you opened the secondaries by hand at 3000 rpm, well yeah the rpms will jump just as they would if you opened the primaries. You proved nothing with that test. We are all telling you the carbs are working like they should yet you are determined to get those stinking secondaries open whether it needs it or not. Here is how I prove to customers the secondaries are useless:

Take boat out on water, go to full WOT RPM. Take note of rpms and speed. Then return to dock. Insert a screw or small bolt in the linkage forcing the secondaries to open at wide open throttle. Take boat out and advance throttles SLOWLY because the carbs don't have pumps built into the secondaries and the engines will simply die of fuel starvation if you try to accelerate to quickly. Go all the way to WOT. Unless something is seriously wrong you will still have the exact same rpm and speed. Your motors can only use the amount of air and fuel the math says they will draw. Most primary bores will feed that easily. I built a pretty cool 389 stroker motor for my boat and used the same 625 Holley. It doesn't open the secondaries.

This is the general formula for how much CFM your 5.7s need: Engine size (CID) x Max RPM /3,456)= CFM. Some folks like to figure in Volumetric effeciency so therefore: Engine size (CID) x Max RPM /3,456) x VE = CFM
A 350 with a VE of .75 (Yours are probably less) = 380 cfm. You have 625 cfm carbs most likely on there now. I guarantee the primary bores provide more than enough by themselves.


I suspect you're like a lot of folks who think the secondaries are supposed to open when the throttles are advanced all the way and the boat is accelerating. That's not how it works. Even Rochester QJets have a restrictor flap so the engine wont 'bog' when those huge secondaries open up fast. If you buy double pumpers and fall for some idiot in a speed shop who says "850 double pumpers are what you need yes siree, Sh** why not a couple of 1250's bro? Spin those props right around!" You may as well mail your money to me because that will do about the same amount of good. Secondaries only help at high rpm, and then only if the motor demands more cfm than the primaries can feed it. Forcing the secondaries open will cause a bog and a big loss in "getting on plane" performance. Just because someone says they hear that bog when they open does not mean they are getting a performance gain. Carburetion is without a doubt the most widely misunderstood system on any motor, bar none. Look at TBI and fuel injection throttle bodies... there are no secondaries. In fact my big ol Triton V10 just has a small single throttle opening.

So why are 4bbls even on these motors? They're a selling point. That's it. People demand them so by golly they're gonna supply them and folks gonna pay for them. Now, granted some 2 bbls indeed are smaller than what the motor can use, so going to a 4bbl that happens to have bigger primaries will get a gain in top speed. You can achieve the same results with a larger 2bbl and a lot less money.

I suggest you pay more attention to the ignition advance curve which can give you a noticeable gain if its not properly set up already.

http://www.automotiveu.com/PickingCorrectCarb.htm
 

aerobat

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If you opened the secondaries by hand at 3000 rpm, well yeah the rpms will jump just as they would if you opened the primaries. You proved nothing with that test.

but he stated he opend the secondaries by hand being at WOT - so the primaries are already full open here for sure. if the rpm jumps up something is odd. but i question myself how he does it since assuming a correct prop 3000 rpm and full throttle is only a transient , no practicable way to keep the engine at 3000 and WOT in a steady condition unless you seriously lug the engine with a way to big prop.

for the rest i agree with you , saw it. a friend in our marina ordered a used 750 cfm holley 4bbl for his mercruiser 5.7 hoping to go ballistic and ended up frustrated , the carb virtually drowns the engine and no setup possible - its a way to big carb for his engine. so less can indeed be more.
 
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I think people is right about these 350s not needing secondaries. I played with the spring kit last weekend and by going considerably stiffer on the spring i got it running a lot better at wot. Before i coulnt get past 3/4 throttle without bogging. Now it bogs for a second and then it takes off like a rocket. Next weekend im trying the stiffest spring in the kit. Ill let you guys know how it goes
 

hall832

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I appreciate you long and detailed response.

1. I am being told this boat would get 4200 rpms on both motors.
2. I have run the scenario that not enough vacuum is created to open the vacuum secondaries.
3. I have talked at length with the Engineers at Holley and Indmar. So i know I am not barking up the wrong tree. I am just a little frustrated.
4. As mentioned before Took boat out and running at WOT 3000. rpms manually lifted vacuum and got an additional 500 rpms. (so i feel the secondaries are needed to achieve the desired 4000-4200 rpms)
5. set timing 10-32 as per Sam at Indmar.

thanks again for your detailed response.
 
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I know it sounds stupid but have you checked if the throttle cable is actually opening the throttle all the way? If you are holding the secondaries open and it revs up maybe your problem is on the cable not opening the primaries all the way.
 

JustJason

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You need to take this one from the top and run a compression test first, and then have a look at your gear reduction, props, and see what your boat should be running for a prop. After that, look at your fuel quality and delivery, and the very last thing your going to look at is the secondaries on the carb. The secondaries are only going to open up if there is enough load on the engine without the engine actually being overloaded. (and there is a difference between those 2 points)

The other thing to keep in mind is if the engine and carb are properly set up, you really shouldn't be able to feel them "kick in". Secondaries are there to lean out the engine, and make it a little more fuel efficient. But they are not there to build power. Your Holley carbs are fine, they will do everything they need to do to allow the engine to spin full rpms. And the (majority) of your problem is not in the carbs, its elsewhere.

If you really really end up hating these holley carbs I will take them off your hands =)
 
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hall832

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thanks Jason for the Reply, I am at my wits end. Props are correct. Compression is right on. Bottom of the boat is clean. Its a 34 Hatteras. Timing is 10-30.
 

hall832

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update.
OK Holley's are running good. Starboard motor running perfect. Port motor IS still struggling. I set the base time at ten. I put a new module in. Checked advance under a load and i am only getting a advance of 12-12 degrees.. no where near the 20 degrees i am supposed to be getting.
 
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