Onan Diesel Generator ( MDKAU) Impeller Replacement

[DiveCuda]

Love this forum--thank you to all the boat techies that take the time to write down their solutions...

Now that we've had our new to us Sea Ray 340 for a couple of months, it was time to start the monthly maintenance drill. Our 2006 Sea Ray has a wonderful set of Yanmar diesels to push her along and a solid Onan Diesel generator (5Kw) to support all of our electronic goodies. Weekend before last, we were doing our Saturday AM boat checks before launching, fired up the generator, and zap...instant generator shut down. Having serviced a few water propelled craft, my husband and I looked at each other and both said "impeller" instantly. We cruised on out into Tampa Bay sans air conditioning for the weekend thinking it would be a quick fix on Sunday afternoon....not so fast....:smt021

After a quick scan of our library of boat maintenance manuals, and more than a couple of hours drilling deep into the internet on Onan generators, we discovered two things: our generator is an older model (2001) and more importantly, there were no service manuals available on-line for viewing or purchase. The Onan site points you to finding a local dealer; we did, and you must order through your dealer. Well, that was two weeks ago. We ordered the manual; still have not see the manual, and being brave, impetuous and bold, decided to go for it regardless. Two weeks later, working a little each evening, our genie is up and operational again, and we have A/C as summer approaches on the bay...okay, the "how to" fix it story.

First, the generator and how to get into the generator . NOTE: the generator is behind the lift arm for the engine hatch. In order to repair the generator, you must be able to get into the generator box. Feeling like I had just stumbled across a Chinese puzzle, I was a little frustrated Sea Ray hadn't provided a few "hints" in their multiple manuals. See the black handle behind the lift to the left of the air flow opening? That handle must lift OUT and then pull up in order to take the front panel off. Notice how the handle is wedged up against the lift....:smt089

While Onan had provided convenient access points on top and on the side, thanks to Sea Rays interesting choice of location for the genie, in order to open the panels, you must take the box apart by removing three screws-- the three screws hold the upper bar frame in-place. Remove the two screws at the top, just left of the front access hatch AND remove the screw at the right hand (aft) end of the frame as well.

Now the top bar lifts out as well as the top access plate. Next, lower the hatch approximately 12 inches very slowly! (Yes, this is a two person job.) That moves the lift rod just far enough forward you can now pop the latch on the front access panel. (The clearance is less than a 1/4 inch, but it will open if the hatch is closed down sufficiently to move the bar over.) Now you can lift the front access plate out while your partner lifts the hatch again. In order for the hatch to come free, the hatch must be all the way up as you lift it up and out.

Gee, wasn't that easy.... Now you have access to the generator parts and pieces, but no manual and more than a few surprises. Our raw water internal hose inbound to the pump had split and the previous owner had managed to bind the hose together with two hose clamps. Only semi-successful, the interior of the box was eaten up with rust from salt water spray. Meanwhile, the search for "why" did the impeller implode revealed a raw water strainer that had possibly never been cleaned out. Plugged only begins to describe its condition.

I didn't start taking pictures soon enough to share the rust shots and plugged sea water strainer, suffice it to say that without Boeshield T-9 and a Graco wrench we would have never gotten the strainer apart. At one point, we seriously considered replacing the whole strainer. :smt101

Tmrw night I'll walk through the process of actually replacing the impeller and where to look for all those little parts that quickly head up-stream after implosion.

For those of you that are curious, this boat was inspected by a highly respected local surveyor and for the most part, she is truly in exceptionally good shape. The diesel engines are rock solid and the electronics on the boat are all in great shape. Cosmetically, the boat hasn't lost her good looks. With that said, our generator reminded us that a great boat is only as good as her "routine" maintenance allows her to be....more tmrw night, and have you checked your sea strainer filters lately?

DiveCuda Sends from the good ship, Kama Hele
:smt024

 

[Hampton]

This is going to be a great and informative thread. Thanks for taking the time to share what you've learned. I just bought my boat and had FULL service done to the engines and generator. When I took delivery, I traced a small leak to the genny intake hose next to the genny itself. The dealer cut the other end off and pulled it tight to fix the leak at the other end. I replaced the hose. The leak is fixed. The bilge is dry.

The dry bilge: In my 340, the bilge was dry unless it rained or unless I hosed down the transom. I never figured out exactly what the path of the water was. Frank W recently told me, "A dry bilge is a good thing." There is a lot more to this statement than the obvious. If you keep track of every little leak and fix them early, your boat will tell you when there is an issue that needs to be addressed. This would have helped your PO greatly and saved you your current head aches.

On another note, my 340 had a lot of signs of corrosion in the ER when I bought it - brackets, painted surfaces... The PO used it for diving and I suspect they allowed a lot of seawater to drain into the bilge (maybe through the transom?). I cleaned it all up and sprayed it with protectant after re-painting the surfaces that needed it. That may help you as well. Please keep up with the photos and descriptions. Not a lot of people have diesel 340's, so any further info on those would satisfy some curiosity.

 

[DiveCuda]

The rest of the story....sorry for the delay; that whole work thing gets in the way of my primary reason for being--being on the water. Thanks John for the encouragement. Hopefully, this will save a few broken knuckles and distressed significant others (what! no AC?). :smt043

Okay, once you have the genset box opened, the only way to access the impeller is by removing the water pump. Loosen the bolt on the upper right pulley wheel. Remove the wheel, and drop the belt. Next, remove the larger bolt; in this picture, the bolt over the right pulley wheel, and then the two smaller black bolts on the front spacing plate. You see them to the left of the wheel.
The next part is just a real joy. In order to remove the pump itself you must remove the bolt at the bottom of the pump plate. This bolt is held on my a nut at the back of a spacer bar. I had to reach under the pump and using an open ended socket wrench hold the nut in place. There is a flat washer and a lock washer under this nut. All of this is blind from the forward view. :smt089
One suggestion, I just had the oil and filter changed when I purchased the boat. I believe this nut would be easier to reach if you removed the oil filter. However, as the oil filter was new, I opted to give it my best shot leaving it in place.

Finally, remove the hose clamps on the upper hose (raw water) and lower hose, slip off both and the water pump slips out. Whewww...This picture is turned counter-clockwise 90 degrees so you can see the upper hose I'm removing.The lower hose is out of sight.

The impeller is on the back side of the pump under a small protective plate. This is where we also found part of our problem. The raw water hose had a split in it right below the right angle. The previous owner had made an attempt to stop the leak through the use of two hose clamps. The clamps had nearly rusted through and the interior of the gen-set box was extremely corroded.
:wow:
This hose makes a hard right ankle coming up from the bottom of the box. At the base, it connects directly behind the fuel filter. Again, to remove the hose, I used a nut driver to remove the hose clamp and very important, used a rubber compatible grease to slip the new hose on.
I also use a good amount of the grease (Ace Hardware, .99 cents) on the impeller and the old tie band trick to help fold the impeller down and push it into place.
By the way, the old impeller had imploded. I found three of the four missing arms in the water pump itself. The forth was recovered from behind the heat exchanger plate behind the water pump.
Fortunately, Onan puts a protective grid over the water path at this point. It captured the one stray rubber arm, and unless the piece was very small, would probably capture the majority of pieces.
You then reverse out the whole process replacing the water pump, the bolts in reverse order and finally, the pulley wheel and belt.

While I had the box apart, I cleaned up as much rust as possible and repainted
with a good coat of Rust-Oleam. There was sufficient rust that I am not convinced that the paint is simply holding it all together.

Would I want to change the impeller at sea? No. But at a peaceful anchorage, anchored in for the night, yes I would. The Onan generator itself appears to be fairly bullet-proof. It’s unfortunate the apparent long-term salt-water spray had saturated the interior of the box. Our concern is this probably took some hours off of the generator in the long term, as smaller components, nuts, bolts, hoses etc. were “distressed.” Time will tell....:smt001

ear

 

[Four Suns]

You may want to get the religion on a few products. I am a big fan of this:

http://boeshield.com/

But last year started using this as well:

http://www.corrosionx.com/marine.html

It's not as waxy as T-9 but I'm not convinced it lasts as long. Anyway, I go through several cans of this stuff every season. Every time I work on something, I spray it down with that stuff when I'm done. Looks like your generator could use a can or two...

 

[Hampton]

Well done on impeller and on post - thanks.

 

[DiveCuda]

Funny you should mention Boeshield; I went through a can on this job. I had not heard of Corrosionx...I'll give it a try. And I particularly like the supplier--True Value. I try to use Ace and/or our local hardware stores for as many products as possible. We find they not only still have service with a smile, they beat any marine store hands-down for price.
We're going to nurse this genset along we hope for several years. And BTW, this should be a positive statement for Onan--just like the old Timex commercial, takes a licking, keeps on ticking...
ear

 

[emotive]

Love this forum--thank you to all the boat techies that take the time to write down their solutions...

Now that we've had our new to us Sea Ray 340 for a couple of months, it was time to start the monthly maintenance drill. Our 2006 Sea Ray has a wonderful set of Yanmar diesels to push her along and a solid Onan Diesel generator (5Kw) to support all of our electronic goodies. Weekend before last, we were doing our Saturday AM boat checks before launching, fired up the generator, and zap...instant generator shut down. Having serviced a few water propelled craft, my husband and I looked at each other and both said "impeller" instantly. We cruised on out into Tampa Bay sans air conditioning for the weekend thinking it would be a quick fix on Sunday afternoon....not so fast....:smt021

After a quick scan of our library of boat maintenance manuals, and more than a couple of hours drilling deep into the internet on Onan generators, we discovered two things: our generator is an older model (2001) and more importantly, there were no service manuals available on-line for viewing or purchase. The Onan site points you to finding a local dealer; we did, and you must order through your dealer. Well, that was two weeks ago. We ordered the manual; still have not see the manual, and being brave, impetuous and bold, decided to go for it regardless. Two weeks later, working a little each evening, our genie is up and operational again, and we have A/C as summer approaches on the bay...okay, the "how to" fix it story.

First, the generator and how to get into the generatorView attachment 19257. NOTE: the generator is behind the lift arm for the engine hatch. In order to repair the generator, you must be able to get into the generator box. Feeling like I had just stumbled across a Chinese puzzle, I was a little frustrated Sea Ray hadn't provided a few "hints" in their multiple manuals. See the black handle behind the lift to the left of the air flow opening? That handle must lift OUT and then pull up in order to take the front panel off. Notice how the handle is wedged up against the lift....View attachment 19258View attachment 19259:smt089

While Onan had provided convenient access points on top and on the side, thanks to Sea Rays interesting choice of location for the genie, in order to open the panels, you must take the box apart by removing three screws-- the three screws hold the upper bar frame in-place. View attachment 19263 Remove the two screws at the top, just left of the front access hatch AND remove the screw at the right hand (aft) end of the frame as well. View attachment 19261

Now the top bar lifts out as well as the top access plate. Next, lower the hatch approximately 12 inches very slowly! (Yes, this is a two person job.) That moves the lift rod just far enough forward you can now pop the latch on the front access panel. (The clearance is less than a 1/4 inch, but it will open if the hatch is closed down sufficiently to move the bar over.) Now you can lift the front access plate out while your partner lifts the hatch again. In order for the hatch to come free, the hatch must be all the way up as you lift it up and out.

Gee, wasn't that easy....View attachment 19262 Now you have access to the generator parts and pieces, but no manual and more than a few surprises. Our raw water internal hose inbound to the pump had split and the previous owner had managed to bind the hose together with two hose clamps. Only semi-successful, the interior of the box was eaten up with rust from salt water spray. Meanwhile, the search for "why" did the impeller implode revealed a raw water strainer that had possibly never been cleaned out. Plugged only begins to describe its condition.

I didn't start taking pictures soon enough to share the rust shots and plugged sea water strainer, suffice it to say that without Boeshield T-9 and a Graco wrench we would have never gotten the strainer apart. At one point, we seriously considered replacing the whole strainer. :smt101

Tmrw night I'll walk through the process of actually replacing the impeller and where to look for all those little parts that quickly head up-stream after implosion.

For those of you that are curious, this boat was inspected by a highly respected local surveyor and for the most part, she is truly in exceptionally good shape. The diesel engines are rock solid and the electronics on the boat are all in great shape. Cosmetically, the boat hasn't lost her good looks. With that said, our generator reminded us that a great boat is only as good as her "routine" maintenance allows her to be....more tmrw night, and have you checked your sea strainer filters lately?

DiveCuda Sends from the good ship, Kama Hele
:smt024

 

[emotive]

View attachment 155873

I thought this might be helpful. I have a full original manual. When I go back to work I can scan and email if anyone would like it.