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G20 Reduced Flow Under Load

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    Posted: July-13-2018 at 10:57am
Hi,

I have been running my '76 Martinique about 4 days a week since May and decided to put in a new impeller. PCM 302 G 20 Sherwood (I think it is G20, has key, pin, and snap ring on pulley)

I ran into this overheating under throttle issue about a month ago when I swapped the impeller.   I unhooked the hose between RWP and TSTAT housing at the TSTAT end and saw about 3" water column at idle and drop down to a bubbly trickle as soon as I opened the throttle. This is consistent with the boat getting hot while skiing then creeping right back down to 160 and holding at low RPM. I do not have a in line strainer, just the grate, the thru-hull pickup, the hose-trans cooler, the RWP. I pressure connected the garden hose to where the intake hose attaches to the thru hull. I hose clamped it and quickly found that I had poor sealing on the RWP housing and disassembled it. Not having a new gasket, I used blue RTV. I also had to drill and tap one of the 1/4 20 holes that had been stripped. Threw It back on, and all was well for the last 15-20 hours of operation.

Now it is back and I need some advice..

I have pulled it apart several times cleaned and re-sealed it (with RTV, real gaskets are in the mail on the way) I cleaned and prepped the surface and followed the directions, not a hack goop job. No leaking at pump. I checked all hose connections upstream of pump and all were tight. I pressure tested with my graden hose, which was hooked directly to my residential pressure tank, and kinked the hose out of the RWP. This let me put the system under significant pressure and there were no leaks. I also pulled my pump off, put my hand over the discharge and sucked in the pump and it did not suck any air through the pump body. I also checked to see if impeller was spun on hub and was not able to break the impeller loose with all my strength holding the pulley and keyed impeller and turning in opposite directions

Pump doesn't leak any water out the shaft seal.

Is the internal pressure that high I am still sucking air because of a bad case seal without an OEM gasket? Air leak through shaft seal at high RPM? Any other good way to eliminate sucking air upstream without just replacing all the hoses and connections? I have the parts needed for the major rebuild ordered and can use the press and other machine tools at work but I am not sure that I have identified my root cause.

Really wishing my cousin didn't pick this weekend to get married in MI or I would be at Green Lake tonight and have this taken care of by the pros.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: July-13-2018 at 11:22am
Cole,
I feel your idea of the seal sucking air at the higher RPM has merit. You mention that it doesn't leak water and it may not but still suck air. Can you detect any shaft runout in the seal area? Proceed with the major rebuild and report back after the wedding!!


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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: July-13-2018 at 12:43pm
Thanks Pete,

The RWP pulley doesn't run true to the other pulleys. There is slop at the pulley hub and I noticed it was missing the snap ring and the pin is worn. I can't feel any slop between the bearings and the shaft but have not done any measurement.

The bracket shows some wear but I don't think it needs to be machined or replaced. I have read other posts about shimming the pump housing with washers. I will try that when I rebuild the pump. If the seal has gone bad and is the culprit I would assume it is from being ran out of alignment.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: July-13-2018 at 1:00pm
Agree with Pete. Also make sure you’re using a good Pcm/sherwood impeller and not an Aftermarket (Sierra).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 2:00pm
I forgot to order the "thrust washer" I think its PTFE but maybe steel. Any chance anyone on here has one on that they are able to get dimensions off of so I can get one from Fastenal or Mcmaster? I will have all the parts and the tools to begin after work tonight so If I can get it locally, it would be great. It is Sherwood part 4264. It Is the washer that goes between the seat and snap ring. Otherwise I will have to get it apart and then measure. I know this is a long shot...

Hope y'all had fun this weekend!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 2:10pm
Cole,
I have to assume it didn't come in the major rebuild kit you ordered. If so, it's not a wear part so you could reuse the one in the pump?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 2:19pm
If it’s the same as a g21 pump it is brass and can be reused
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 2:40pm
Originally posted by wiscofoot wiscofoot wrote:

I forgot to order the "thrust washer" I think its PTFE but maybe steel. Any chance anyone on here has one on that they are able to get dimensions off of so I can get one from Fastenal or Mcmaster? I will have all the parts and the tools to begin after work tonight so If I can get it locally, it would be great. It is Sherwood part 4264. It Is the washer that goes between the seat and snap ring. Otherwise I will have to get it apart and then measure. I know this is a long shot...

Hope y'all had fun this weekend!!


No such thing as a long shot around here

Here's a picture with some dimensions written down.



This came in my major overhaul kit from Sherwood by the way

Like Gary said, it's brass and if there's not one in your kit, it should be reusable
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 4:20pm
Thanks a lot Ken. I have several good impellers and didn't need a new cam so I did not buy the kit. I also needed hardware for the pulley assembly (G20) that didn't come in the kit.

I bought new bearings, seal and seat, several new gaskets and O rings, and all the retaining clips and pins. We will see how this strategy pans out. I will update later. Thanks again.

Cole
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 4:21pm
DO NOT remove the pulley.
I made up a plate to set the pump in so that the pulley clears. This is not an impossible job but care is needed,if done wrong you can crack the housing.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 5:48pm
Take your pump apart as far as you can and hold loosely in a vice. Pry as much of the seal as you can out. It will look like this-


Then you can reach in and remove the thin steel retaining housing with a punch,might have to do some prying,just have to be careful not to get overzealous. It will look like this with it out-


Now you will be able to reach in and remove the snap ring and using a press like in the first picture remove the shaft with the pulley still on.

Remove the big snap rings that hold the bearings in and the press them out,I start them off like this just to get them moving



Then switch over to my plate to get them completely out of the housing,be careful not to loose the spacer that is between the two bearings





I have a blast cabinet so I clean up the housing and paint,you can just wire wheel or wire brush it



With it cleaned up they go back together way easier than coming apart,assembly is the reverse of taking them apart When replacing the seal I use a short piece of 1" plastic pipe so that it presses on the outside housing of the seal but yet clears the pulley shaft.



This cheap Harbor Freight press has already paid for it's self when I replaced the front axle u joints on my Jeep. Now everything it does is free
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 6:12pm
Gary

I will not remove the pulley as of right now. Currently it wobbles on the shaft, is missing snap ring, and has a mutilated pin. Key and set screw are ok. Should I just put the new snap ring on and try to pound the old pin out with the new one?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 6:16pm
I have seen the more detailed discussion on the other site

https://www.planetnautique.com/vb5/forum/nautique-topics/maintenance-technical-discussion/11121-rebuilding-sherwood-raw-water-pump/page2

My assumption was that the use of the key, set screw, pin, and snap ring meant that it wasn't an interference fit between pulley and shaft.

I have the Sherwood procedure and also the info from plantnautique. I will stand by..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 6:22pm
Just saw all your photos Gary. Thanks. I have the press and 1" pvc ready to go. I will try to duplicate what you have there. I don't really want to make a fixture like that nice one you cut out of the channel.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 6:26pm
None of the 6 that I have done Cole had a pin,they were all interference fit with a snap ring. Don't follow the Sherwood book literally They have you install the seal then the snap ring that is under it next,just put it together in the order you took it apart.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 6:28pm
Your 76 had a keyway and set screw just like you describe on the OEM pump.

In later years they went to a pressed on interference fit pulley.

You might need a new pulley .or some machine shop work since it's wobbling on the shaft.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 6:35pm
To press the seal back in I used a 1 1/4" piece of plastic pipe...... sorry about that
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 6:45pm
And............you can still buy the pulley, Here's an EBAY link

link
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 6:46pm
Ahh. I am going to try and remove the pulley if it comes off easy.

So when you press the shaft out with the pulley on, are you just breaking off the snap rings on the pulley side?

The Sherwood instructions/graphics look so much easier and prettier than your real life photos/practical insight.

I’m aware there is potentially damage to the shaft or pulley already.

If I get the pulley off and on easily, is it easier to do the rest of the work according to the Sherwood instructions?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 6:49pm
No you should still remove them first. You pull the seal,remove the snap ring under it and push the shaft thru the bearings then you can remove the snap ring. As to their method,don't know never attempted to remove pulley,your on your own

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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2018 at 9:39pm
Wisco

One thing to keep in mind is that you're talking G20, Gary is talking the later G21.

There are other small differences in the pumps like you'll probably find a spacer between the pulley and the outer bearing while the later ones have no spacer but a snap ring instead

The spacer plate between the body and the housing is different and the body itself is different where the spacer plate sits.

None of this really makes any difference as long as you're careful taking it apart and noting what goes where.

And do it the way Gary said and you'll be fine. Even with the pulley off, you still disassemble the same way .
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: July-17-2018 at 10:57am
Gary freaked me out so I went back to basics and replaced the wear plate (was very different than what it had), cleaning up all the RTV, and carefully reassembling it all without messing with the seals and bearings. I shimmed the bracket so it ran much more true and also put the snap ring and tightened the set screw on the pulley and shored it right up. I hooked it up and still did the same thing...

I was piZZZZed off and had the engine at about 1800 RPMs on the trailer and I reached down and felt the flex hose between trans cooler and pump. It was collapsed. I had never been reaching around down there with the engine running except at idle. Some of the wires had delaminated near the connection to the oil cooler and at around 1200 RPM and higher the suction of the pumps folds it in like a wet noodle. At idle and shut off the hose felt and looked firm. Like Pete says....if in doubt replace the hose!!! Consider this one closed
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: July-17-2018 at 11:08am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-17-2018 at 12:29pm
Did your old wear plate or spacer look like one of these and the new one look like a different one of these?

The round one with the little locating tab came out of a G20 from 1976



And for your engineering mind here's a good drawing dated 1979 in the link

It shows the bigger triangular plate instead of the round one so there were ongoing changes over the years just like with everything else in the world except for some guy named Pete

link

Oh yeah.....................never say "consider this one closed" till you've had it on the water in real life conditions. You don't want to jinx yourself.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: July-17-2018 at 12:56pm
I have that drawing printed on an 11x17” sheet on my desk at work right now. The original spacer plate is the round one with no holes. I replaced it with the symmetrical triangular one. Paid a few bucks extra to get the special hose from skidim that says Pleasurecraft Marine Engine Company. The hose that failed was a precut automotive wire reinforced that looked out of place anyways. Maybe someday this site will support mobile photo uploads and I will have a field day.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: July-17-2018 at 10:30pm
The hose that was on there was a 1-1/4 x 30” (poorly) wire reinforced auto radiator hose that have soft ends for the connections. This morning right away I ordered the 1.25x36” pcm hose from skidim. Did some searching and then realized the oil cooler and rwp are both 1” connections. I will figure out a way to plumb it but what type of hose do you guys run on older boats? Corrugated or non corrugated? Wire reinforced the whole way? Also it looks like if I come straight out of the heat exchanger with a more rigid type hose, that it will interfere with the routing of the oil lines that go to cooler. ‘76 302
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-17-2018 at 11:45pm
I'd tell you what I use but it would just start a long discussion full of disagreement about suction hoses so we'll let you get some answers from others.

I don't have to worry about poking myself with a piece of wire though
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: July-18-2018 at 11:33am
To each their own. I am curious though, the wire stuff is nasty to work with but I have been replacing every hose on the engine with it because POs used trash and it has caused me downtime and headaches. The first suction hose, J hose connection and one wet exhaust tube came with regular rubber hose. I ordered a 5’ stick of the 1” gates wire green stripe with my amazon prime day order.. I will replace the soft hoses downstream of RWP with the extra I have left over so they match and someone else can fight with getting off in 20 years.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-18-2018 at 1:02pm
Well, since you're curious, a long time ago( that translates to 35 or so years) I had a problem with the original wire reinforced hose from the transmission cooler to the RWP leaking.

The wire was poking out through the outer layer of hose and the inner layer was cracked and that made for cooling issues if you know what I mean..

Not having the internet to educate me and not liking that wire reinforced hose, I used some 1 inch heater hose. Double layer with fabric reinforcement in between.

I never had any issues with collapsing the hose due to RWP suction vacuum. and have used the same stuff on multiple boats over the years.

The "canned response" is you gotta use wire reinforced to avoid hose collapse but the only way the hose might collapse is if it's bent around to tight a radius and kinked or if your suction path from the lake/river is blocked by let's say weeds or plastic or you have a through hull shutoff that you managed to leave shut.

By the time you might have an issue with the hose,collapsing you've probably fried the impeller anyways from lack of water going through it from any of the above causes.

As long as the hose can withstand about 10 inches of vacuum and you have water flow through it, it ain't gonna collapse.

The double layer heater hose is easier to tighten down and get a good seal especially on things like the brass hose ends of the transmission cooler as compared to the wire reinforced stuff.and It can easily withstand the vacuum one of these pumps draws.

If I had a really tight radius, I'd go for the wire reinforced but it's pretty easy to avoid the tight bend radius with a little thought put into the hose routing and length used..

I do keep a piece of wire reinforced hose around though to remind myself how much I dislike the stuff

I pulled it out just before I wrote this.

So, yes wire reinforced works just fine but it's not for me.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: July-27-2018 at 7:12pm
Originally posted by KENO KENO wrote:



Oh yeah.....................never say "consider this one closed" till you've had it on the water in real life conditions. You don't want to jinx yourself.


Yeah...so...:I am done not being a good listener to you guys. I replaced the collapsed hose with the special PCM hose, took it to the lake and it did the same thing. At this point I took a step back and realized I need to be systematic and go through it start to finish.    Turned out there was a big old ball of fishing line and Lake Winnebago trash and weeds at the front of the trans cooler. I feel very stupid for not checking that first Pulled and cleaned and ran it on the trailer, Confirmed full flow. Took it to the river last night and ran it for half an hour and it is fixed.   I don’t know that my hose was ever failed just that the vacuum caused by the clog was enough to make it fold in. This has been a valuable learning experience.

Either way after all of this is done, now my rwp is weeping like a Bears fan. Thankfully I have the parts to rebuild it but for now I will run it as is until I have a lull in use and a surplus in free time. . Is a 1 ton arbor press adequate for the job?
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