Onan Generator Access

[Steve Murphy]

Am going to replace the Onan diesel generator exhaust system, starting with the riser, on my '77 42' Double Cabin. Has anyone found a way to access the forward (exhaust) side of the generator? On looking it over, it appears the only way to get reasonable work access is to disconnect it and possibly slide the entire base plate around or else maybe cut an access hole through the bulkhead behind the port/aft seat. If anyone has a better way than trying to move the beast, I would appreciate the advice.

[Kevin McIntosh]

Steve ... I'll be watching your thread with interest ... my Onan MDJE 7.5 kW genny is situated (more like shoe-horned) Stbd. Fwd. in the engine room ... I bought an endoscope just to be able to check the heat exchanger coolant content / level ... as the access for that is a little round sheet metal cover in the Onan Sound Shield directly above the h.e. cap ... all the way Fwd, roughly centered in the O.S.S. and a couple of inches from the e.r. ceiling ... just getting a hand in there to move the cover and release the cap is a big challenge (for me, anyways, big guy, big hands) ...

My access options are similar to yours ... on the '79 DCS, the dinette was situated Stbd. (mine was all removed in favour of a A-I-O washer/dryer & a trash compactor) and the only way I can see to get at the genny w/o (partially) removing it is to make (an) access hatch(es) in the salon floor above the genny, and/or in the dinette Aft bulkhead into the e.r. ahead of the genny.

Presumably Uniflite had no plan other than to remove the genny for anything other than minor servicing ... or some wiry little mechanics to squeeze in there ... your job sounds like the (partial) removal variety ... maybe consider just removing it completely and going with something new(er) and more compact.

FFF

[Steve Murphy]

I was able to wedge myself in between the engine and the Onan to see the exhaust setup. Wondered if I was going to call the FD to get back out:-)  There is really no way to actually work back there so it looks like removing the whole thing piece by piece, cutting an access hole, or moving the whole unit are the two options. If the heavy mounting plate underneath can be rotated, that seems like the best option. Will try that first with the help of a come-along but will still have to get back there to disconnect the old exhaust. The unit, I understand, works and has few hours. So it would be nice to leave it in place. If it turns into a real Magilla, will wind up removing it pc.by pc. and using the space for something else.

[Steve Murphy]

Hi Kevin,

Well, I was able to access the generator, also a 7.5 Onan. My unit is mounted on a steel plate which sits atop a plywood shelf on the port side right against the engine room/galley bulkhead. The plate is attached by three hefty wood screws to the base. After removing the screws/clamp pc., I was able to use a regular framing size flatbar to get under the plate and lift it enough to start getting a few 3/4" black pipe couplings underneath. It moved quite easily once the rollers were positioned in the right direction. I managed to caddie-corner it enough to get behind it. Next time I have to access it I will have some better pipe pcs but this seems to be the way to move it. The unit hour meter has very few hours on it so it is probably worth it to renovate it. I removed the exh. manifold and installed a new riser. Next,will put in a Vetus muffler. It does not appear that there was ever a muffler so the Vetus should quiet it down. The engine runs like a top and it is putting out juice.

Steve M.

[Kevin McIntosh]

On Mon, Nov 30, 2020, 21:05 PST Kevin L. McIntosh wrote:

Hey Steve M. ... glad to hear progress is being made ...

So ... were you using black iron pipe nipples? to roll the unit around and out?  3/4 NPT nipples?, or, actual 3/4" O.D. pipe pieces?  How long would you say they would need to be to work best, and, how many is "a few"?

I'm surprised Uniflite didn't install one of those Onan Aqua-Lift muffler systems on your setup ... they did on mine (early 1979 build) ... my gen-set is installed ahead of the Stbd. 6-71N engine, otherwise sounds pretty much identical to yours.

Did you have any trouble sourcing the new exhaust manifold and riser or was it just the riser than needed replacement?

I'll have to examine the base of mine and see if the plate is held (clamped?) to the plywood shelf by 3 wood screws like yours was ... don't suppose you took any pics of same eh?

Kevin Mc

[Kevin McIntosh]

On Tue, Dec 1, 2020 3:59 AM (EST?) Steve Murphy wrote:

They were 3/4" npt couplings that were floating around in the bottom of my toolbox. So thought would give the roller idea a try. I got four of them under and was able to rotate them so they were rolling in the right direction. The flat bar works very well for the lifting.  Once hammered under, it can be levered to easily lift the base up enough to get a roller under. The next time, will use some longer pipe pieces, maybe 6" or so. Some sort of bar or even wire can be used to manuever the rollers around. 

  I did not need to replace the manifold, just the 1-1/4" close nipple and riser. New risers are still available for these old units.

  All in all the job was much easier than expected once the thing was rolled out where it was accessible. I will also be screwing some blocks around the base plate to secure it better.

[Kevin McIntosh]

That's all great info Steve ... looks like you were up later than me ... couplings eh?  so female / female 3/4 NPT ... got it ... like I said, I will examine the base of my gen-set and get back to this thread with any new observations (that differ from yours) ... and hopefully some pics ... Kevin Mc