Boats For Sale:
What Jets should I use?? |
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MaddMarxx 
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Joined: June-29-2006 Location: United States Status: Offline Points: 1741 |
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 Topic: What Jets should I use??Posted: February-13-2009 at 12:11am |
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Does anyone have an idea on what jets I should run in my 715 holley duel feed carb, it has 65s in the front and 68s in the back right now, but I think I could go bigger!
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jbear
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Joined: January-21-2005 Location: Lake Wales FL. Status: Offline Points: 8193 |
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Posted: February-13-2009 at 2:22am |
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I think this carb is not good for your boat in my expert opinion.....might make it to fast.
john |
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"Loud pipes save lives"
AdamT sez "I'm Canadian and a beaver lover myself"... |
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79nautique
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Posted: February-13-2009 at 12:14pm |
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bump them up one - two sizes, I believe I had 72's in my single pump, but if you still have the stock cam then I wouldn't get to crazy, maybe one size larger on the secondaries.
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TRBenj
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Posted: February-13-2009 at 1:30pm |
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MM, is that a 4160? I assume so. Sounds like you have a rear metering block conversion on that thing? You must if you have replaceable rear jets instead of the plate.
If thats the case, then (by memory) I think Im running 68 in front and 74 in the rear. I posted my numbers on here at one point- Ill see if I can find them. The rear needs to be ~6 steps bigger to make up for the lack of PV. I turn up to 5200 without any problems. Admittedly, I havent done a good plug chop yet, but performance seemed to improve as I went from overfat (72/82) down to this point. Holley's general recommendation was to go marginally fatter than stock (66/72), so this is pretty consistent with that. |
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backfoot100
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Posted: February-13-2009 at 5:54pm |
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Tim,
I talked with Mark last night about this. I completely forgot about the lack of a PV without the metering block. Good call!!!!!! |
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When people run down to the lake to see what's making that noise, you've succeeded.
Eddie |
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LaurelLakeSkier
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Posted: February-14-2009 at 9:44pm |
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I'm quite sure the power valve only affects the primary side no matter if you have the standard metering plate or the conversion block. It opens to give the richer mixture to the primary circuit about the time the secondaries begin to open up.
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TRBenj
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Posted: February-16-2009 at 12:32pm |
Thats correct. No PV in the secondaries means that the jets need to be larger to balance them out. |
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reidp
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Posted: February-28-2009 at 11:36am |
Mark, while all of the previous jet suggestions sound good, if your main objective is to run with the Boatdr, I suggest your only option is to go with one made by Pratt and Whitney. Just in case....... http://www.pw.utc.com/vgn-ext-templating/v/index.jsp?vgnextoid=c3ca34890cb06110VgnVCM1000004601000aRCRD |
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eric lavine
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Posted: February-28-2009 at 1:24pm |
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I gotta laugh, im taking what appears to be a 650? marine and a 600 auto and combining the 2,i hope to end up with a good carb, im using the float bowls from the auto, drilling the base on the marine for vacuum, too cheap to buy another carb so I'll give this a shot on a buick 350. both carbs are in new condition. there definitely was a difference in the CFM of the carbs because the marine was around .050 larger. i need to run the numbers. will post in the future if it will even start lol
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"the things you own will start to own you"
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jbear
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Joined: January-21-2005 Location: Lake Wales FL. Status: Offline Points: 8193 |
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Posted: February-28-2009 at 2:39pm |
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Still think this is a bad idea...way to fast.
MM...did you see the thread about the distributor? I think I might need this...what do ya think? john |
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"Loud pipes save lives"
AdamT sez "I'm Canadian and a beaver lover myself"... |
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Rick
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Posted: March-06-2009 at 2:56am |
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Make sure the Carb is Marine. Automotive carbs are built so that if there is to much gas it spills it out of the carb down the intake to the ground. For obvious you don't want this to happen in a boat because it fills the bilge with gas... Not a good thing. You need to make sure the throttle shaft isn't grooved and the overflow is curved back into the front barrels. Holley sells this tube if you need it.
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SS 201
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Posted: March-10-2009 at 9:39am |
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GOOD POINT
THE DIFFERENCE BETWEEN AUTO AND MARINE IS J TUBES TO PUT THE FUEL BACK IN THE CARB RATHER THAN BILGE. ALSO MOST MARINE ARE ALREADY SET A LITLE RICHER THAN AUTO. BEFORE JETTING UP OR DOWN BE SURE TO READ THE PLUGS FIRST. PLUG GAP AND ELECTRONICS CONTROL THE PLUG READING, SO TOO MUCH FUEL WITH A LOW VOLTAGE OUTPUT WON'T BURN PROPERLY. ALSO THE FUELS TODAY DON'T ALWAYS SHOW GOOD READ, ADD A LITTLE OCTANE BOOSTER AND IT WILL CLEAN UP THE BURN.WILL SHOW REDDISH COLOR WHEN JETTING, HELPS WHEN CHECKING PLUGS. |
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MaddMarxx
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Posted: March-11-2009 at 1:50am |
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Yes it is a marine carb it was off of my buddys Donzi, and it had really big jets in it, so when we rebuilt it we down sized the jets, I just have not had the time to work out all the bugs out, I do have to do good plug check, but it seemed to be running lean!
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SS 201
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Posted: March-11-2009 at 9:14am |
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MOST 600 CFM NON REAR PLATE USE STOCK 65 F 76 R.
GO TO MORTEC.COM IT CAN ANSWER MOST ALL OF YOUR CARB QUESTIONS. AGAIN REMEMBER YOU ENGINE CONDITION AND IGNITION CONTROL HULL ,PROP ARE FACTORS IN THE JETTING OUTCOME. BIGGER NECESSARLY IS NOT BETTER.WHAT ONE RUNS DOES NOT NECESSARLY FIT YOUR NEEDS. LOTS OF VARIBLES GO SLOW IT IS CHEAPER THAN MAKING RASH OR COPY CAT DECISIONS.BEEN THERE DONE THAT. |
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MaddMarxx
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Posted: March-11-2009 at 11:17pm |
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Its a 715 cfm!
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SS 201
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Posted: March-12-2009 at 5:06pm |
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715 72 f 84 r
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boat dr
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Posted: March-12-2009 at 10:24pm |
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Mark , I may be out of line here , but why not put the 4160 back on it. You do not have enough mods on the motor that would require the extra CFM nor the hassles that go with the jetting.
One more thought , those bowls with the external float adj. are not marine complient.Did you not loose MPH by adding this carb? Unless there were major issues with the stock put her back on. My stroker is moving a lot more air and turning 5900 rpms with a stock, YES STOCK, 4160 and as you know who took the trophy home..........Boat dr |
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eric lavine
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Posted: March-13-2009 at 12:02am |
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we did some calculations with boat weight to engine ratios doc, your boat should actually be doing around 70, you sure your plugs are OK?
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"the things you own will start to own you"
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boat dr
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Posted: March-13-2009 at 3:16am |
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Eric, I have done more running than calculating. But read them and weep...
12x15 @5000 rpms =66.25 actual 53.02mph 12x15 @5100 rpms =67.61 actual 54.08 12x15 @5400 =71.59 actual 57.27 12x15 @5600 =74.98 actual 58.96 As you can see there is a big difference between theoretical MPH based on pitch and RPM and actual GPS speed. The slippage rate climbs very steeply after 4500 rpm's. 20% or so down low then climbing as you spin it higher........ |
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LaurelLakeSkier wrote: