Electronic Conversion Kit
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Boat Maintenance
Forum Discription: Discuss maintenance of your Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=2223
Printed Date: January-16-2025 at 12:06am
Topic: Electronic Conversion Kit
Posted By: subli572
Subject: Electronic Conversion Kit
Date Posted: August-09-2005 at 8:08pm
| Hi, I have a '89 Ski Nautique and recently I changed for an electronic ignition, everything seem to be great, the only problem is that the engine is running up to 5000 rpm so it seems that the propeller is too small, I changed for a 14x16 three blade propeller and the rpm got down to 4600, the engine manual says that the maximum rpm must be 4400, I would like to know if any of you had the same problem and if you recommend me to use a bigger propeller, if so please tell me what size and if a three or four blade propeller. |
Replies:
Posted By: surroundsound64
Date Posted: August-09-2005 at 10:05pm
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My 81 never had that problem... Just don't throttle it up that much. Or maybe I'm misunderstanding why it's reving that high. ------------- 1981 Ski Nautique 2000 SAN Looking for a 2000-2006 SAN |
Posted By: joel
Date Posted: August-11-2005 at 2:13am
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What prop did you have that put you at 5000 rpm's? What motor do you have? You are correct don't get over 4400. If you have a 351. Good luck don't hammer it till you get the right prop on your boat. I would call the guys at SKIDIM. They are great. and they could help with problem
Joel ------------- Joel |
Posted By: stang72
Date Posted: August-11-2005 at 3:17am
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I am soon to install my EI ...should you expect to see higher RPMs...I have always heard the performance does not differ much.
Stang72 ------------- stang Face plants are not that funny when it's you face! http://www.correctcraftfan.com/diaries/images/3720/photo1.jpg" rel="nofollow - The Super Air |
Posted By: nates78ski
Date Posted: August-11-2005 at 8:56am
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Changing the ignition system should not effect the rpm that much. I would check the tachometer for accuracy first before I drop the cash for a prop.It is possible the e-ignition is causing a inaccurate reading or the old system was the cause. Either way check the tach with another unit(handhead is OK) just to verify the possible problem. I have not see a conversion increase RPM very much. ------------- Nathan http://correctcraftfan.com/diaries/details.asp?ID=1463&sort=&pagenum=3&yrstart=1978&yrend=1978" rel="nofollow - My '78 Ski Nautique <a href="http://photobucket.com/Nates78ski" rel="nofoll |
Posted By: surroundsound64
Date Posted: August-11-2005 at 3:14pm
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The ei emits a different sound frequency that I suppose could mess with other stuff. Double check to make sure it's the right part #. ------------- 1981 Ski Nautique 2000 SAN Looking for a 2000-2006 SAN |
Posted By: David F
Date Posted: August-11-2005 at 4:50pm
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Tach readings come from the coil, not the ignition module. Points or electronic should nto make any difference in tach display. The coil fires 4 times (isn't that right with four stroke?) per crank revolution regardless of ignition type. The tach uses this pulse interval to determine RPM.
Disclaimer: I think I have this right. Anyway, tach should read the same regardless of ignition type. |
Posted By: subli572
Date Posted: August-11-2005 at 5:06pm
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Thank you all for your answers, my boat engine is Ford 351 and the propeller that gave me 5000 rpm was a four blade 13 x 13, and now that I changed for the three blade 14 x 16 the engine feels better and the rpm fell to 4600. ------------- |
Posted By: captan1
Date Posted: August-12-2005 at 2:26pm
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I converted to a Mallory Unilite and have noticed some funky readings now and again, especially at idle, I think there's a filter of some sort to correct a points/EI conversion if some part doesn't like the swap.
------------- http://www.correctcraftfan.com/diaries/details.asp?ID=452&sort=&pagenum=1&yrstart=1978&yrend=1978 - 1978 Ski Nautique |
Posted By: Guests
Date Posted: August-12-2005 at 5:37pm
There is a rule of thumb that an inch in diameter will result in a change in rpm of approx 600 and an inch of pitch will change rpm approx 200. Based on this rule of thumb your rpms shoud have decreased about 1200. Now, i'm certainly no expert and i dont know what impact switching from a four blade to a three blade might have although i do think a three blade would spin easier. Nonetheless, i would have expected a much larger change in rpms with that drastic of a prop change.
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Posted By: nates78ski
Date Posted: August-14-2005 at 1:47pm
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FYI. Tach readings are taken from the negative side of the coil. Tachs read a difference in dwell off/on time within the coil. This signal(dwell) originates in the points on an older system. Your tach is simply a volt meter designed to reconize the variances. Dwell is the measurement of the time ths points are closed, which causes the magnetic field within the coil to collaspe in the primary side of the coil and cause an increase in voltage(spark to the plugs) on the secondary side of the coil. Any increase in dwell will retard the timing & decrease in dwell in increase the timing. This is how on board comtuters adjust the timing electronicly on the car you drive. Just thought you might like this info. PS/ there is no "sound frequency" involved in the ignition system. ------------- Nathan http://correctcraftfan.com/diaries/details.asp?ID=1463&sort=&pagenum=3&yrstart=1978&yrend=1978" rel="nofollow - My '78 Ski Nautique <a href="http://photobucket.com/Nates78ski" rel="nofoll |
Posted By: Guests
Date Posted: August-17-2005 at 6:16pm
| shouldn't the coil be changed with the EI, I know there are specific coils for made for EI and for points |
Posted By: Guests
Date Posted: August-17-2005 at 6:40pm
| THE BOAT CAME WITH A 14X16 BECAUSE OF THE 1.23-1 TRANSMISSION. YOU WILL HAVE A MARGIN OF 10% + OR - READING ON THE TACK. YOU ARE RIGHT ON THE MARK WITH WHAT YOU HAVE NOW. YES THERE IS DIFFERENT COILS FOR POINTS AND ELCTRONIC. BUT YOU CAN USE THE STOCK COIL IF YOU FOLLOW THE INSTRUCTIONS THAT CAME IN THE KIT. |
Posted By: subli572
Date Posted: August-18-2005 at 1:41pm
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Thank you for your answers, I decided to buy an OJ 14 x 16 four blade propeller. ------------- |
Posted By: Guests
Date Posted: August-18-2005 at 11:36pm
| Just my two cents - my local marine engineer (who has tremendous experience) claims that many marine engines (right up to multi 1000 hp diesels) come with slightly large props to keep rpm down and avoid warranty hassles. He says all the American V8s will happily spin to 5000 and in fact is planning on machining our prop down to achieve higher rpm. Not as big an issue as having to small an engine in too heavy a boat but restricting the rpm with a large prop can actually cause them to run hotter in certain circumstances. I know you guys have been running the damn things at 4400 for at least a quarter century with few problems but something to think about. |