95 Sport GT40 rear main leak
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=48892
Printed Date: November-23-2024 at 12:31pm
Topic: 95 Sport GT40 rear main leak
Posted By: Jordanh
Subject: 95 Sport GT40 rear main leak
Date Posted: June-20-2020 at 4:21pm
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Hey guys, I have a GT40 that I am getting a small amount of oil droplets on the underside of the bell housing. It is not yet dripping bit after an hour or so of operation I can wipe my hand under the bell and come up with oil on my fingers. I assume this is from the rear main. It's definitely engine oil. My question,. How would you guys proceed to fix this. I would like to pull the engine and just do an overhaul. It has 850 hrs on it. Imo id rather pull it once and put it in fresh. My dad, and other friends, seem to think this is ridiculous and keep telling me to pull it, pull the pan and do the seal, and install it. What would everyone do if it was theirs ? ------------- 95 Sport Nautique |
Replies:
Posted By: desertskier
Date Posted: June-20-2020 at 5:57pm
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Unless your engine needs to be rebuilt which with only 850 hours would be unusual I would just replace the seal. Pretty sure you don't have to pull the engine just the transmission which isn't that hard to do. ------------- 92 SN - Owned since 93 99 Pro Air 89 SN - Went to live on a lake in Texas 75 Donzi 16 - Sold in 93 |
Posted By: Gary S
Date Posted: June-20-2020 at 6:00pm
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Listen to your Dad. 850 hours is nothing. No need to remove pan either,remove the trans maybe lift rear of engine if needed and replace seal. Put everything back -check alignment your done. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: 8122pbrainard
Date Posted: June-20-2020 at 6:20pm
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Jordan, I know you have mentioned it's engine oil but are you sure? Brownish would be engine and reddish would be trans fluid. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Jordanh
Date Posted: June-20-2020 at 7:02pm
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100% it's engine oil. I changed the VR1 and trans fluid at the beginning of the season . If I wipe the bottom of the trans with a white cloth it's golden brown . I will take my dad's advice and just change the rear seal. Full disclosure I don't have alot of experience with marine(automotive) engines. I've only built an SBC from a short block. I do consider myself fairly mechanical tho... But I was completely under the assumption that you had to remove pan and loosen the mains to change the rear seal for whatever reason. So I'm excited to hear I don't have to hoist the engine completely out of the boat. Now that's I've actually searched on what's needed to do that I feel foolish. ------------- 95 Sport Nautique |
Posted By: KENO
Date Posted: June-20-2020 at 7:48pm
Like Gary said........listen to Dad but not to everything he said  The thing that hasn't been mentioned is that you have a later 351W with a one piece rear main seal, and that's the reason it can be replaced without dropping the oil pan. As mentioned you can jack up the rear of the engine a little and let it pivot around the front mounts which you loosen. Then click on the links below, one has a post from somebody with the same name as me, giving a pretty good rundown on how to access and change the damper plate. The info is near the end of the thread. Being a GT40 you may have a few more things to remove but it's a good rundown of what's involved. Once you're looking at the plate, you would remove that and then the six bolts holding the flywheel to the crankshaft and a rear main seal will be staring you right in the face. You can use a pick to remove the old seal and then put in the new one. You'll be laying on the floor to do it, but it's not bad. Follow the instructions for whatever seal you decide to use especially if you decide to use a teflon rear main seal since they need to go in place clean and dry unlike a rubber seal that gets lubed up good before putting it in. When it comes time to put the flywheel back on, make sure you've read the second link which talks about bolt hole spacing. It only goes on one way. And then since you have a damper that's getting old and they just fail whenever they feel like it, I'd install a new damper. if you don't put a new one in, the old one will crap out about a week later and leave you doing most of the job all over again.........or maybe it'll last 10 more years, you just never know You could get the damper from Skidim as one place to shop. You need the damper for a PCM 1.23 to 1 transmission As far as seals go, here are some part numbers from National Oil Seals, (they make FelPro's seals for them) National 5278 is a Teflon seal that some will say is the latest and greatest technology National 2377 is a rubber seal that works well too. http://www.correctcraftfan.com/forum/forum_posts.asp?TID=42615&title=damper-plate" rel="nofollow - link http://www.correctcraftfan.com/forum/forum_posts.asp?TID=47807&title=holes-dont-line-up-on-new-flywheel" rel="nofollow - link And while you're in there it would be a good idea to look at the front seal on the transmission to see if it leaks at all and decide if you want to replace it. |
Posted By: KENO
Date Posted: June-20-2020 at 8:02pm
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Here's a link to the damper plate at SkiDim. It's fairly pricey, so the choice is up to you https://www.skidim.com/prodinfo.asp?number=R140016A" rel="nofollow - link And another link for the transmission front seal at SkiDim https://www.skidim.com/prodinfo.asp?number=R047185" rel="nofollow - link |
Posted By: gun-driver
Date Posted: June-20-2020 at 10:12pm
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Been there done that Sorry to hard to put them in order on my phone but you get the idea. Almost forgot the one with the seal https://ibb.co/vH76JcX" rel="nofollow">  https://ibb.co/sqRJ147" rel="nofollow">  https://imgbb.com/" rel="nofollow">  https://ibb.co/wNxxJDq" rel="nofollow">  https://imgbb.com/" rel="nofollow">  https://imgbb.com/" rel="nofollow">  |
Posted By: Jordanh
Date Posted: June-22-2020 at 2:52pm
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Thank you all for the info! I will certainly replace the seal and damper while in there. I have a slight vibration around 1000-1200 rpm. Things ive tried to remedy this.. Align prop shaft coupling ( was done on trailer, i have since read that this should be done on the water) changed plus, dist cap, and rotor. changed fuel filter ran seafoam through gas checked propshaft run out swapped props to a new prop to eliminate prop as issue. I pulled the pin and ran the engine at 1200 rpm. didnt seem to have a vibration. so im thinking its something from the flywheel back. Now, could this actually be a damper issue? It is smooth and noise free when shifting into gear. ------------- 95 Sport Nautique |
Posted By: 8122pbrainard
Date Posted: June-22-2020 at 3:26pm
Jordan, Did you check the shaft aft of the strut? That's where most bends occur and where even a slight bend produces the most vibration. The max TIR is .003" anywhere on the shaft. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Jordanh wrote:Posted By: Jordanh
Date Posted: June-22-2020 at 7:12pm
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I pulled the prop and checked the shaft directly aft of the strut, right before the prop, and on the prop mating surface. ------------- 95 Sport Nautique |
Posted By: 8122pbrainard
Date Posted: June-22-2020 at 7:38pm
That's were the bend in the shaft occurs so you probably didn't get a good reading You what to measure farther back on the taper. What reading did you get? ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Jordanh
Date Posted: June-23-2020 at 1:14am
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Can you describe in greater detail where you are wanting the shaft measured? I measured it in three places between the strut and the prop nut. I did this as preventative maintenance last year when I aligned my engine. My vibration has been noticably worse this year. I've owned the boat 7 years and have not hit anything. Honestly if the prop shaft is bent I would be absolutely baffled. I didnt get deep into the details in my previous post. I just figured I'd leave it at the fact that I measured the shaft. ------------- 95 Sport Nautique |
Posted By: 8122pbrainard
Date Posted: June-23-2020 at 7:10am
Jordan, This is a good spot. Wish you had mentioned it before. So, what did you get for the runout? ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Jordanh
Date Posted: June-23-2020 at 8:29am
I think my wording was just bad, in this comment I was attempting to describe three places but I see now it doesn't read well. If my memory serves me right all measurements were .0022" TIR or less. ------------- 95 Sport Nautique |
Posted By: Jordanh
Date Posted: June-23-2020 at 8:35am
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There was a video on this site of a gentleman aligning a coupling and checking runout that I followed when I did it. I did all this on my trailer. I have since learned that the coupling alignment is best done in the water as your trailer may not support your hull in the straightest fashion. I am going to recheck that coupling over the fourth ------------- 95 Sport Nautique |
Posted By: 8122pbrainard
Date Posted: June-23-2020 at 10:07am
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Jordan, Still regarding the vibration, while it's still on the trailer and if you get a chance, check the runout on the shaft again. As far back on the prop taper will give you the best results. The TIR is .003". A bent shaft aft of the strut and a out of tune prop will result in the most vibration. Also, did you lap the prop to the shaft? Is the prop all the way forward on the taper? When installing the prop, some have found that the key gets shifted out of the keyway so the prop rides up on the key so the prop isn't seated on it's taper. http://www.correctcraftfan.com/forum/forum_posts.asp?TID=12866&KW=proper+prop&PID=145077&title=proper-prop-installation#145077" rel="nofollow - Here's a thread on proper prop installation. Regarding alignment on the trailer VS: in the water, I'm not a firm believer in checking alignment again in the water. With the hull just sitting in the water or on the trailer, is a lot different than when it's underway. On partial plain, on plain, wide open, and turning at different speeds produces variations in hull geometry way beyond the on the trailer VS: in the water check. The only gain I feel you may find is when the stringers are deteriorated to the point that a large geometry change confirms there's a problem. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Jordanh
Date Posted: June-26-2020 at 12:58am
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I will go through that lapping process next weekend as well as verifying my keyway fitment. That is a fantastic write up. I will report back with my results. I'm not sure I will be able to get my dial indicator on the shaft next weekend. I won't have anywhere to mount it with the boat on the lift and I avoid the ramp like the plague on holiday weekends but will verify it when I get a chance. ------------- 95 Sport Nautique |
Posted By: 8122pbrainard
Date Posted: June-26-2020 at 7:37am
It can be done on the lift but you need to get wet. The dial indicator base is clamped to the strut which is the best place to clamp it in or out of the water. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: KENO
Date Posted: June-26-2020 at 8:17am
That's the most profound statement I've heard all day, but the day is still young So, anyways, thanks Pete, it'll make me chuckle on and off for a while And.........I'm not picking on ya, it's just funny |
Posted By: Jordanh
Date Posted: June-26-2020 at 5:41pm
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I'm actually afraid to melt in the water ... I only have a mag base for my dial indicator so I have been placing it on the prop guard on my trailer. I suppose I can always clamp themag base to thee strut or something. I'll fashion something up that's stable enough. Not sure I want to take the risk of my Brown and Sharpe indicator taking a bath though. ------------- 95 Sport Nautique |
Posted By: 8122pbrainard
Date Posted: June-26-2020 at 5:49pm
------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Jordanh
Date Posted: June-26-2020 at 5:53pm
I'll get an extra hand and give it a go. I don't want my indicator to take a bath ------------- 95 Sport Nautique |