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onan 7.5 MDJE needs help


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  #1  
Old 03-20-2014, 11:04:26 AM
blaise805 blaise805 is offline
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Default onan 7.5 MDJE needs help

Hi new guy here could use some help. I have the 7.5 MDJE generator serial number 1269187916. The generator has seized and is mounted under the floor in the galley of an old boat. I would like to know first of all are rebuild parts available for the engine. There are no manuals on board so I will need to find some way to get the specs. The second thing is can I remove the engine from the electric plant without taking the entire unit while in place. I think it would almost impossible to remove it as a complete unit. I have everything ready to come out but would like some insight. Thanks for any help in advance.
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Old 03-20-2014, 11:19:23 AM
Kevin K Kevin K is offline
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Default Re: onan 7.5 MDJE needs help

Your generator was made in December of 1969. If you post the complete model number, and an email address that can accept large attachments, we can send some manuals your way.
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Old 03-20-2014, 11:24:45 AM
Ted_Cool Ted_Cool is offline
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Default Re: onan 7.5 MDJE needs help

1: Can usually be fixed. Parts are getting hard to find, but you're at the right place.

2: Separating the genset while in the hold would not be my choice. I'd rather rebuild the decking if necessary. How was it installed to begin with?
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Old 03-20-2014, 11:30:48 AM
Billy J Shafer's Avatar
Billy J Shafer Billy J Shafer is offline
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Default Re: onan 7.5 MDJE needs help

Spent many hours cussing out boat builders.Unless you can find a way you will have to remove it in pieces.Done that many times and it is not fun. Parts are out there you just have to look.

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Originally Posted by Ted_Cool View Post
1: Can usually be fixed. Parts are getting hard to find, but you're at the right place.

2: Separating the genset while in the hold would not be my choice. I'd rather rebuild the decking if necessary. How was it installed to begin with?
Most of the time. The idiots put the generator in the worst place they can find. Then build the boat around it.
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Old 03-20-2014, 12:53:58 PM
Kpack
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Default Re: onan 7.5 MDJE needs help

Does the gen have a lot of hrs ? Could be a piston stuck at the top.
When you post a email for the manuals let us know the part numbers you need.
S&r sales and some others have old new stock but its pretty high if you find it.
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Old 03-20-2014, 01:07:19 PM
blaise805 blaise805 is offline
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Default Re: onan 7.5 MDJE needs help

Thanks for the quick replies here is another set of numbers 3cr/z2688 I'm not sure what I will need yet. To remove the unit out in one piece would be very difficult. I think damn near impossible without tearing up the inside of a beautiful boat so if I can remove the engine that's do able. The generator was working fine and the owner went to start it next trip and no go. I take care of the machinery for him and its locked up solid.
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Old 03-20-2014, 01:20:05 PM
Kpack
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Default Re: onan 7.5 MDJE needs help

If you could get to the top of the piston to see if its stuck on the ridge it would help.
You can take a 2x4 and hit the piston and knock it loose but your taking a chance if its still hooked to the crank.
If it were mine and a 69 model and it was that hard to get too I would by a new 1800 unit if that much stuff has got to be torn out.
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Old 03-20-2014, 02:28:38 PM
Ed Sparks Ed Sparks is offline
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Default Re: onan 7.5 MDJE needs help

possibly hydrolocked by water getting in past the vacuum break on the exhaust.
Could try pulling the injectors and spinning by hand with a socket on the end of the crank to see if water comes out. At least you might find out why it's locked up and develop a plan from there.

As Billy said. Most gensets in boats are put in places where they are damned near impossible to work on them.
You will lean many new curse words working on boats as you lean down through small scuttle hatches at arms length.
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Old 03-20-2014, 09:43:22 PM
blaise805 blaise805 is offline
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Default Re: onan 7.5 MDJE needs help

Yes I'm well versed working on boats I ran dive boats for years in the channel islands off California. I tried to turn the crank but no luck. I think if I can see a manual and separate the engine I could get that out and rebuild it if possible.
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Old 03-20-2014, 10:34:23 PM
yellowlister yellowlister is offline
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Default Re: onan 7.5 MDJE needs help

I would pull the injectors (as Ed said) and valve covers before u decide to pull it all apart.. start simple and go from there... maybe a stuck valve or you have water in the cylinder or something else that could be a easier fix.... was it running when it locked up or did it sit for awhile?

Worst case scenario... Your in luck.. im about an hour from Oxnard.., actually use to live in Port hueneme and happen to know where 4 of your generators are if you need any parts or a complete engine or etc... they were pulled from 2 yachts being overhauled a few years ago and have had a nice resting place stored inside.. all were runners when removed and I think one only has 400 ish hours..
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Old 03-20-2014, 10:40:47 PM
blaise805 blaise805 is offline
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Default Re: onan 7.5 MDJE needs help

Wow that's great I think my guy would probably buy that low hour runner and I could switch them out in the boat

---------- Post added at 07:40 PM ---------- Previous post was at 07:38 PM ----------

I think he ran it low on oil there was very little on the stick
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Old 03-20-2014, 10:50:39 PM
Ed Sparks Ed Sparks is offline
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Default Re: onan 7.5 MDJE needs help

Ouch they don't like running out of oil.


I was stationed at port who needs me back in the 70's and lived on saviers blvd
in Oxnard for a couple years.
MCB 3
31st NCR
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Old 03-20-2014, 11:06:10 PM
blaise805 blaise805 is offline
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Default Re: onan 7.5 MDJE needs help

Oxnard has not changed much except its tripled in size since then. I try to stay by the beach side of town
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Old 03-21-2014, 10:29:21 AM
Ted_Cool Ted_Cool is offline
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Default Re: onan 7.5 MDJE needs help

Would it be reasonable / acceptable to create a proper access hatch in the floor for the generator?

Careful cutting with a thin kerf saw would leave you with a panel that could be edged and finished nicely.

The owner would be trading the carpenters time for the mechanics time, but it would make future maintenance so much easier.
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Old 03-21-2014, 10:51:25 AM
blaise805 blaise805 is offline
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Default Re: onan 7.5 MDJE needs help

There is a hatch off to the side that is really close in size and it was more than likely used to drop the unit in. I have enough room to turn the unit side ways to disassemble. I have to work sitting or on my knees. once the generator is split in to two halves it would be much easier to remove. The inside of this boat is to nice to cut open and there is a full size refrigerator above the genset.
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Old 03-21-2014, 12:40:27 PM
Ted_Cool Ted_Cool is offline
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Default Re: onan 7.5 MDJE needs help

If it went in through the hatch, it should come out that way too!

Maybe this is like putting an engine with a transmission in a car - it has to be tipped down to hook the end under the opening.

Perhaps you can get some slings securely fastened to allow that.


I hate to say it, but it might be time to replace the Onan and let it find a home where it can be maintained more easily.

Have you looked at the Kubota diesel powered gensets that Phasor Marine and others make?

Good luck either way!
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Old 03-21-2014, 03:13:05 PM
John Ward John Ward is offline
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Default Re: onan 7.5 MDJE needs help

Quote:
Originally Posted by blaise805 View Post
Thanks for the quick replies here is another set of numbers 3cr/z2688 I'm not sure what I will need yet. To remove the unit out in one piece would be very difficult. I think damn near impossible without tearing up the inside of a beautiful boat so if I can remove the engine that's do able. The generator was working fine and the owner went to start it next trip and no go. I take care of the machinery for him and its locked up solid.
The "z" is wrong, needs to be a number, possibly another 2? And it needs to end in a letter.
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Old 03-21-2014, 03:23:19 PM
blaise805 blaise805 is offline
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Default Re: onan 7.5 MDJE needs help

how about 3CR/2268B
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Old 03-21-2014, 03:39:52 PM
John Ward John Ward is offline
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Default Re: onan 7.5 MDJE needs help

Your build sheet...
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Old 03-21-2014, 06:35:02 PM
Gunny Gunny is offline
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Default Re: onan 7.5 MDJE needs help

Billy nailed it. They ain't boat builders at all. They find a generator and build a structure around it, get mad and toss it into the nearest body of water. If it floats, they call it a boat and sell it to someone. Then folks like Billy and I come up with some brand new descriptive terms describing these builders and their parentage when we have to try to service these "boats".

I'd pull the whole genset and repair it where you can comfortably access all of it. Betting you will find some evidence of past maintenance that will require correction.

Also easier to push over the side if up on the deck when it really makes you mad.
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