How much HP??
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=3313
Printed Date: November-23-2024 at 9:57am
Topic: How much HP??
Posted By: JEFF KOSTIS
Subject: How much HP??
Date Posted: April-06-2006 at 1:10am
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Hello to all, someone must know how much HP can you put into a 71c tranny and a 1" shaft?? They claim they are designed for small blocks, but what is the magic number on the maximum amount of HP in that combination before things go bad?? Thanks in advance for any replies.
Jeff... ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Replies:
Posted By: bkhallpass
Date Posted: April-06-2006 at 1:30am
Well Jeff, you've got two boats. Let's use one for an experiment and find out BKH------------- Livin' the Dream |
Posted By: Martinique87
Date Posted: April-06-2006 at 1:39am
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Hey Jeff,
You might have already seen this but according to the manual a 71C is rated for up to 255 hp, a 72C up to 380 hp. Seems a little low for the 71C, can probably handle more but don't know how much more. Tim |
Posted By: GottaSki
Date Posted: April-06-2006 at 10:15am
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I can confirm a '85 2001 with the factory 425 HP engine, 72C and 1" shaft, used mostly for footing over 45 mph and no problem with shaft, perhaps 11-1200 hours. Its seen lots of hours at and near full power.
The extra 2 disks on the 72 certainly is a plus After having a 71C open I can see it depends on it condition...130 psi line pressure is normal hot, a gauge can confirm. If a new reg spring doesn't help, the pump is tired and can compromise the whole thing. Shimming or replacing the regulator valve can get a few more psi over stock..since they see over 200 psi cold, a little more won't hurt it if you monitor the temperature. Depending upon the thickness of the clutch pack, properly shimming the forward clutch pack to the drum should aid holding pressure, more pressure is transfered to the disks and less pressure is wasted on the the diaphram spring. I recently found my 850 hour 71c with fiber disks will certainly slip long before a freshened up one. I suspect a freshened 71c can handle smallblocks in the low 300hp range quite comfortably for a decade or more. I don't see anything internal that is significantly weaker than the 72, minus the 2 forward plates. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: JEFF KOSTIS
Date Posted: April-07-2006 at 1:23am
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Thats guys.. Thats great info!! Gottaski, the reason why I ask is because the 300hp new 350 PCM bobtail in the 76 will make this clinging/pinging sound at WOT, but cant confirm where the noise is cause it so dam loud. The tranny was original with 450 hrs behind a 302 and looked clean when I dumped the oil and poked around. Would there be anything in the 71c that would cause a noise like that?? All I have to do is back off the throttle a hair and it goes away. It seems when the 4 barrels are wide open is when it does it the worst. I have however had nothing but trouble so far with that engine and now the starter is dead after one season of 75 hrs. It hesitates sometimes real bad on LIGHT acceleration from take-off and will pop. Im still workin with Ski Dim to see whats going to happen. I took the oil pan off to move the drain plug and took out about 4 full tablespoons of liquid metal in the pan-before it even went in the boat! Sorry to get off the beaten path, but was wonderin if the noise could be the 71c.
Thanks!! Jeff... ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: 79nautique
Date Posted: April-07-2006 at 11:25am
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the dampner plate might? should have been replace when the new engine went in I would think. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: GottaSki
Date Posted: April-07-2006 at 4:36pm
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Thats weird. The trans can buzz, but clang/ping doesn't seem right, else it will frag shortly. 79 may be onto something.
What is the ignition advance at idle, 2000, 2500, 3000, 3500, 4000 rpm? What do the plugs look like after a WOT run? Cut the threads off a plug, snap a pic of the soot ring, should be 1.5-2mm wide. Insulator should be white, not grey. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: SS-201
Date Posted: April-09-2006 at 10:37am
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I have used 71C tranny for years up to 500 HP no problems. I have one in my 1931 Chris Craft racing runabout for 53 years, no problems. ------------- SS 201 |
Posted By: JEFF KOSTIS
Date Posted: April-09-2006 at 11:54pm
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ss201, thanks! That makes me feel a little safer. Exactly what I was after.
79, Gottaski, I have a new damper plate that came with the bobtail. Its all new but the tranny itself. I tries the timing light, but noticed they are no markings on the cover like the rest of the engines. I have not played much with the newer engines, but I guess I will have to get a new light or some timing tape. The other issue is I cant realy touch too much on it as its under warranty, and dont want to take the paint off Any of the bolts as it could be used against me. I do know that the advance versus rpm seems correct visually with the light. They did send me another carb and still the same. I do know that changing the flame arrestor to the huge 454 one thats low profile made a difference and unplugging the PCV valve and capping it off made another difference where it runs much better. All parts are new, so seems like a possible valve misadjustment?? It should run 100% being a "drop in" ready to go, all set up and run new engine. I know the plugs when running WOT for a bit then shut down will result in black rear plugs and clean front plugs. Same as the OMC 225 due to the slant of the engine and more fuel going to the rear cylinders. Thanks Guys!! Jeff... ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: SS-201
Date Posted: April-10-2006 at 8:32am
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Carburetor floats are very critical of the heights. A good start is putting a 7/16 drill bit under the floats for a start. Unfortunately the carb doesn't have sight plugs to see where you are. Just turn the adustments down or up a quarter of a flat at a time.
Floats that are high will ruin a good idle and drown the plugs. To see whats going on, put a can of octane boost and after you run it will turn the plug red, Read the plug to see how they color, you can adjust from there.. ------------- SS 201 |
Posted By: GottaSki
Date Posted: April-10-2006 at 10:05am
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Double-hmmm. My plugs are always uniform front-rear. There is something amiss with your carburation because the slant may affect the carb but not the ratios after it leaves the carb.
Sounds like a combination of problems. Not enough initial producing the pop/hesitaion down low. Rich condition on the rear, maybe a touch lean on the front but can't confirm till you cut the threads off a front plug after a WOT run. A lean condition at WOT could be causing preignition on the front, producing the noise you hear. Additionally, as the mix gets more dense at WOT, the flame front travels faster, requiring less advance; now too much initial can produce a knock, or If the span on the distributer advance is too wide. (chevys usually require less final advance than the typical ford windsor, because they breath better, producing a denser mix at WOT) Is it a holley or quadrabog? Run the engine solely on the primaries and see if it behaves. Then do a WOT plug check on just the primaries, see if the plug color now gets uniform front to rear, and measure the soot rings....if too narrow, you confirmed the primary circuit is too lean. Plugs should be white insulator with a 1.5-2mm ring at its base. Just because it may not knock doesn't mean the primaries are ok....check the plugs...the mix is not dense enough to produce the same condition on half a carb. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: JEFF KOSTIS
Date Posted: April-11-2006 at 12:26am
Great info guys, The boats are still in mothballs and will be for a bit yet. I fought with the 74 OMC 225 307 (Quadratoilet) all suummer several years ago and was trying to figure it out. I tried float adj to the point of not running at all (no gas), I then adjusted each secondary metering rod after a test run and spark plug inspection. Come to find out, I adj the secodaries until the lean mixure (bogging when WOT) disappeared and had great punch to it, without going too rich. It runs great and no matter what, the reor plugs would have black carbon on then, while the fronts were clean. Now, the rear plugs electrodes are clean and nice, but around the outer part its black. The new 300 hp PCM 350 (Holley)from Skidim last year does the same thing in the 76. I assumed its the gas pouring in an favoring the tilt of the engine like the OMC 225. The OMC carb has a wedge (factory) and sits level. Maybe thats why a EFI has a large advantage in HP for the same engine??? If I keep the secondaries closed, all plugs look the same and nice..WEIRD???? Maybe the gas isnt atomizing well when the secondaries are open and causing it to favor the rear?? 
Jeff.... ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: GottaSki
Date Posted: April-11-2006 at 10:27am
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Yes, its sounding more like the secondaries are rich. But, that wouldn't cause noise.
Your clean insulator and sooty base suggests one throttle position is rich, then at some other position leans out and gets to temperature then self-cleans the insulator. The secondaries will show their colors on the rear plugs before the fronts, there is just no reason for the mix to cross paths under the primary. I've seen front plugs show lean because a PVC line was plumbed to an intake runner instead of the spacer or carb - that leaned just two cyllinders causing detonation, but lack of vacuum at WOT made the problem go away. But that doesn't sound like your 350's problem. Is it a 4150 (two metering blocks) or 4160 (one metering block, one metering plate)? ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: reidp
Date Posted: April-11-2006 at 1:15pm
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Jeff,
Just try adding one cubic inch to the displacement and see if that doesn't clear it all up. Just kidding.......... ------------- ReidP /diaries/details.asp?ID=231&yrstart=1971&yrend=1975 - 1973 Mustang |
Posted By: jbear
Date Posted: April-11-2006 at 2:48pm
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ReidP: Spoken like a true Ford lover, just like the jbear. ------------- "Loud pipes save lives" AdamT sez "I'm Canadian and a beaver lover myself"... |
Posted By: JEFF KOSTIS
Date Posted: April-12-2006 at 1:06am
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Well, I think no matter what you have (GM or Ford) they all have equal issues. Scary to say, but I think the Quadratoilet on the OMC 225 is the best yet when set up right. The secondaries open much smooother than the holley on the 76 or the 351's Ive driven in. Its just my opinion, but when they go sour, forget it!! Its funny to believe that the 225 HP OMC will just about keep up with 300 hp PCM in identical boats as far as turning a 12x15 prop.
Gottaski, I believe its a 4160, I know its not the new "fishbowl" type as Skidim calls it. Its just weird as a light accelleration will cause it to die, pop etc every so often. Hard take-off no problem. I was pulling my sister on her show ski outa the hole and she asked why in the heck did I let off on the throttle, as I responded "the engine hesitated and popped through the carb". Im gonna email Ski dim again and see what they are gonna do. CC wont do warrantee work on it since I didnt but it from them, so its tough on who to support around here. Jeff... PS: I still prefer a 307 over a 302!! ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: jbear
Date Posted: April-12-2006 at 2:42am
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Ahhhhh Jeff, to much cold on your brain. Gotta go with Ford Blue.
But you are correct, ya can have trouble with either, Ford or GM, and when ya got trouble you'll do or spend about anything to fix it! john ------------- "Loud pipes save lives" AdamT sez "I'm Canadian and a beaver lover myself"... |
Posted By: SS-201
Date Posted: April-12-2006 at 8:38am
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First the secondaries are controled by vacum. They open only when it reaches the spring tension controling the opening. The secondary opening is controled by the boats engines need for more fuel.This is controled by spring selection, and only then do the secondaries open.
If you would put a vacumn guage it would show you the inch of vacumn. Remembering all boats are not the same ,prop selection, weight, etc. All the answers are a starting point and not carved in stone. ------------- SS 201 |
Posted By: GottaSki
Date Posted: April-12-2006 at 10:05am
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I think when you mash it, the accel pump is compensating for the a lean condition you feel when you go easy-up. The initial timing sounds like it can use a few degrees more advance to make the pop go away, but thats premature until we solve why its clanging at wot.
Final advance needs to be determined - should be around 36 degrees I suspect. If its less then that, then rotating the distributor is warranted. If 38 or over, then I think it could be contributing to the detonation. I agree, you shouldn't have to go through this. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: 79nautique
Date Posted: April-12-2006 at 12:13pm
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Jeff, To me you have two problems the first is a carb issue, lean mixture sitting with a accel pump that is not adjusted correctly, this is causing the stumble and backfire at take off. Secondly you have a timing issue mostly with to much mechanical advance or over timed, causing the ping and all the noise at the top end. Reading some of your old post is this a carb or EFI engine? if it's EFI are you using a mechanical pump or did you add a electric pump. If it is EFI and you are using a mechanical pump that's your problem and adjusting everthing else is a waste of time because your issue not enough fuel pressure. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: JEFF KOSTIS
Date Posted: April-13-2006 at 1:13am
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79, its a new complete carbed engine with everything but the actual tranny. It is supposed to be run, set-up, tuned, timed, rocker arms aligned....EVERYTHING to just drop in and go!! The exact engine is the one in the SkiDim catalog, but was extra for the RH version. It has a electric fuel pump, appears to be the same as the EFI low pressure pump. Everything comes from the factory ready to go, therefore if I do too much playing with it (like taking the fresh paint off bolt heads) they might say it isnt covered since I touched it.
I can say I have tried a new carb sent by SkiDim-still same trouble. To be more specific on what happens also, if I am doing 18 mph and give it a bit more throttle, nothing changes. Give it a bit more and the engine seems to die a bit, then go. It reminds me of a dead spot, but still puzzled because another carb didnt do anything. Thanks again guys! Jeff.... ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: JEFF KOSTIS
Date Posted: April-13-2006 at 1:16am
Sorry to dissapoint you Jbear, but the new engine is all black!!!! Maybe thats the problem!!!
Jeff... ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
jbear wrote:Posted By: GottaSki
Date Posted: April-13-2006 at 11:59am
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Call me crazy but now it really sounds like it has one of those 2.5 power valves in it. PVCO's opening too late, besides other problems. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |