Engine Hesitation in 1994 PCM HO
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=33566
Printed Date: October-08-2024 at 12:53pm
Topic: Engine Hesitation in 1994 PCM HO
Posted By: Harry Squarejaw
Subject: Engine Hesitation in 1994 PCM HO
Date Posted: May-12-2014 at 9:31pm
| OK Guru's.This is the first post for a novice owner of a 1994 Sport Nautique(164 hrs) with a 351/5.8 HO. It is electronic/ Fuel injected into a Holley carb.. The problem is it will do anything but maintain a constant speed. Especially in the 20-30 mph range.It will be running 22 and start to slow. RPM's go down, oil pressure ect.. Give it more throttle and it sort of bogs down, then accelerate like crazy and you reduce throttle and do it all over again. Will run 35-40 all day with no hesitation. It is strong out of the hole... I have changed plugs, elect. diode greased everything I can find, changed fuel filter,oil ect. Im afraid the coil pack could be bad and unfortunately unavailable.How to test? The origional owner said its been like this since 2010 after it "Ran Hot". He had abt 1600$ in new left exhaust manifold and labor done and the motor was "sound" at the Nautique dealer. I find myself sitting in the boat a 2 AM lookin for something else to do. I dont mind spending the money to make it right, just dont have a clue as what to do next.... |
Replies:
Posted By: TX Foilhead
Date Posted: May-12-2014 at 9:57pm
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Certainly possible the ProTec could be causing that. Part of the gains of distributor less ignition is the computer can change the timing in ways that a distributor can't. As far as I know the ProTec does that, but nobody has ever seen exactly when and by how much. It could also be the driver, while inboards make it much easier to hold speed they don't do it automatically at any point you hold the throttle. If you have a Perfect Pass it should make it easy to set the RPM's and see how it holds without anything in tow. I have a pretty stout return spring on my throttle and it will work the throttle back if I take my hand off the throttle, could be something as simple as that. |
Posted By: Harry Squarejaw
Date Posted: May-13-2014 at 1:02am
| I wish it was the nut that holds the steering wheel, but Don't think so. Any way to test the coil pack? I keep hearing that I may need to retrofit to a distributor, but then that would also mean a new carb.... Seems like I'm now pulling off parts , replacing with different and hoping for the best! Hasn't worked so far |
Posted By: Bri892001
Date Posted: May-13-2014 at 1:08am
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Do you have a picture of your throttle body / carb setup? Just to see what you have there. You mention a Holley, which would be a carburetor. But then, you also mention Throttle Body Injection. |
Posted By: Dreaming
Date Posted: May-13-2014 at 3:11pm
If it has TBI, the throttle body is a version of the Holley Projection system. Mine did not perform properly when I got the boat, and suspect that you are having issues with it too. They have been known to go bad. A Holley 4160 carb fits just fine and requires a small modification to the throttle cable mount. If you are having pro-tec problems, ski dim makes a nice kit to replace the whole deal, or you can piece together a carb, fuel pump, distributor and wiring harness set up. it could be as simple as a sensor or clogged injector also, but it's hard to tell what is going on from the OP's post There is another thread on replacing the ignition parts recently. Search for Pro-tech or something of the sort and youll probably find some good help. |
Bri892001 wrote:Posted By: Harry Squarejaw
Date Posted: May-13-2014 at 11:45pm
| Thanks for the words of wisdom. Still not entirely sure if it's the injectors, or pro tech ignition. Prob both....I spoke to a local dealer who rec that I find a mechanic who was trained on that particular motor in 1994. Wow. Any one know a 1994 vintage pro tech/ throttle body injection guru around birmingham al? |
Posted By: TX Foilhead
Date Posted: May-14-2014 at 1:42am
| Just for grins post a picture of that contraption on the engine. To the best of my knowledge nobody has successfully gotten Holley ProJection to work on an inboard boat. These motors are too close to the upper limit of the Hp it can do. If that's what you have it's an easy fix to put a carb on it. If you have the TBI with a ProTec then you have a different issue. |
Posted By: Harry Squarejaw
Date Posted: May-15-2014 at 2:46am
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It is indeed a TBI/ PRoTec combo. Looks kinda like spare parts from a V2 Rockett , and I can't for the life of me upload a pix!! I am quickly understanding that a new distributor kit and carb may be in my future. Had the boat out a total of 2 hrs... Oh well. |
Posted By: Bri892001
Date Posted: May-15-2014 at 10:10am
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As far as posting a pic, it doesn't work from a mobile device unfortunately. Your best option is to email the picture to yourself, gmail etc. Then, go to a regular computer, open up your gmail, then download the pic to your desktop. Then, log on here from the computer. Then look for the Post Reply button, not the default quick reply. Once you get to full reply, you'll see a tree with an arrow. Then button gives you the upload option. Make sure the pic isn't too big. If you happen to have the pic in photobucket, you have to copy the image url and paste it in your post between Img BBCode HTML tags. |
Posted By: Harry Squarejaw
Date Posted: May-15-2014 at 1:02pm
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Posted By: Harry Squarejaw
Date Posted: May-15-2014 at 1:05pm
| Bri892001 Thank you for the instructions! This is the beast. |
Posted By: desertskier
Date Posted: May-15-2014 at 1:36pm
| This is probably a long shot but it is very easy to check and relatively easy to fix. The operating voltage for the Pro Tec system is 12Vdc that is routed through the dash from the ignition kill switch to the key switch then back to the engine. The problem is that due to IR voltage drops by the time it gets to the Pro Tec module it is much less that 12Vdc. If you know how to use a DMM measure the voltage at the 12.5 Amp breaker on the rear of the engine with the key on or at the Pro Tec connector pin "P". It should be close to battery voltage. A low input voltage caused my boat to hesitate and sometime die. After I beefed up the wiring through the dash and to the engine I read 11.6 Vdc at the breaker and have not had a problem since I fixed it (about 12 years and 1000 hours). Another thing you could try is just disconnecting the Pro Tec connector and main engine connector and cleaning them with alchohol then reconnecting them. I did this with mine before I figured out the wiring issue and it would run fine for awhile. |
Posted By: Orlando76
Date Posted: May-15-2014 at 2:02pm
| +1. With what desert skier said. I don't know much at all about the Pro Tec but the wiring to and from dash is always an issue in a CC. Couple that with 20 years of nasty connections and perhaps not a superb battery and the voltage at engine is easily less than 11v. Resistance in a 12vdc system is a b**ch |
Posted By: Bri892001
Date Posted: May-15-2014 at 2:36pm
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+2. I agree. A good idea and about the cheapest possibility on a Protec fix you can find. Also, where this engine overheated at one point. Look extra close at any wiring that touches or comes close to touching the block. It could have melted some wiring insulation somewhere and caused some interference. |
Posted By: Harry Squarejaw
Date Posted: May-16-2014 at 2:05am
| I'm off tomorrow and can't wait to start working on the motor. There was indeed a wire from the fuel pump that terminates in the Pro Tech that looked a bit fried. The plastic conduit was melted where 3 wires were spliced. Woo Hoo!! May be on to something. |
Posted By: Harry Squarejaw
Date Posted: May-29-2014 at 7:40pm
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Thanks everyone for all of the help. I wound up taking it to the doctor and we shall see. Thanks!!!! |