Impeller tolerance

[smackdaddy53]

I finally got to run my jet and it ran fine on the hose but once I ran it in the water for a few minutes the impeller started contacting the liner. I had exactly .030" all around tolerances with my feeler gauge before I ran it. Did the tolerance change because of the load the water put in it pulling it down? Why is there no literature on this anywhere? Good thing I have a stainless impeller and an extra liner.
Thanks

 

[brianb2247]

other than that how did it perform on the water , does it feel like a nemitz class destroyer

 

[blazer02]

Sounds to me like you had something loosen up and it dropped it down.have never heard or water pulling one down unless it was lose.i ment be rong but i believe a stainless can be ran at something like .015 even but not sure.

 

[dhoganjr]

A stainless doesn't flex as much and can run a little closer tolerance. Did you have the nut tight and washer tabs bent around it. If there was anything between the washers sand , grit or anything else could have caused it. In the water as soon as you fire it up it will pull down if the nut not tight. The key could have got caught as you tightened it not allowing it to seat correctly.

Take the shoe off and check everything, make sure it is seated and everything is tight. If it is tight and everything is in place with the correct clearance, it should not hit.

 

[dhoganjr]

There will also be a little back and forth play with the impeller. Grab it and turn it counter clockwise as far as it will go, as this is the direction the water will force it, before tightening it down.

 

[smackdaddy53]

I installed a new bearing kit with all seals recently as well. I was meticulous about assembling and cleaning everything and there was no grit between the shim washers or anything on the drive shaft. It ran fine on the hose but when I got it in the water and started getting on it something did not feel right so I shut it down. The bearing is installed correctly as well or it would have failed already. I ran it slow to get the feel of it for at least twenty minutes and slowly picked up thd pace. I am using the correct lubriplate grease and greased it when I got home and the grease came out clean so it isn't the bearing. I ran it on the hose when I got home with the foot off and it ran like a champ.
Other than this small problem do you guys think a 60/45 Mercury Jet is not enough motor for my hull? I am going to re shim it and do a full day of running and adjusting until I get optimum performance then call it if I need to just get a bigger motor.
I have researched outboard jets for three years and it seems like my motor should perform decent with my hull setup but real world performance of one rig could vary greatly from a hundred others.
Thanks for the replies, I want to keep this thread going until You guys gelp me figure this out. I want to keep the draft as little as possible and get the performane I want if it is possible because this is a poling skiff that needs to float fairly skinny.

 

[dhoganjr]

The 60/45 should push it just fine. Around here guys run them on 1856's and other hulls loaded down because of the 40 hp restrictions on the Current River. Size is not the problem, need to figure out what the issues are and go from there.

I'm not much help on the bearing side, never had to change one, but know that they have to be done correctly or they self destruct quickly. Since you are sure that it is not the bearings, get the reshimming done and go from there.

 

[Brian J]

Try taking one shim out. Had the same problem back in May when I put a new liner in our jet. It would run on the hose, but wouldn't turn over in the water. Switched one shim washer and it was fine.

 

[smackdaddy53]

Thanks guys. Next week I will have a couple of full days I can take it to the lake and run it and tweak it until I get it set where it needs to be. I didn't expect to put it in the water and have it set up perfect. It ran a few laps but never really had enough room to get on plane where I was running. I will touch base again in a few days and get this thread going again. I appreciate the input and keep it coming if you have any thoughts or similar issues that may help me.

 

[Jetboater-TB]

Maybe I missed it, but how do you know the impeller is contacting the sleeve while you're running the engine? What symptoms are you seeing? Are there marks from the impeller contacting the sleeve?

 

[smackdaddy53]

Maybe I missed it, but how do you know the impeller is contacting the sleeve while you're running the engine? What symptoms are you seeing? Are there marks from the impeller contacting the sleeve?

There are grooves in the liner and I can see the deepest ones are closer to the bottom. There was a small wad of aluminum shavings on the edge of the stainless impeller and this is what made the other grooves in the liner. I cleaned it up, removed one washer from the top and added to the bottom and the tolerance is better. I am going to run it tomorrow and see how I need to set my motor to get on plane.
Do you guys really think I need to have power trim to adjust on the fly or is a static setting fine? I see a lot of outboard jets without trim.

 

[dhoganjr]

It will run ok without when you get it set correctly. However, with power trim you would probably gain a couple mph.

The reason is without power trim you have to choose where it performs the best with no adjustments under way. Tucked under gives you the best hole shot without cavitation, best speed and top end comes with motor trimmed level. You have to choose somewhere in between.

With power trim you get the best of both, tucked under on take-off and trim out as it comes on plane. Gives you less shoe in the water for less drag and more clearance, allowing you to run shallower without hitting bottom as much. The more speed you can get the more of the hull will be out of the water.

So to answer your question, yes it will perform, you just won't be able to get top performance out of it. Personally I will never own another outboard without it.

 

[JoshKeller]

how does tilt and trim fair to a direct rock hit? I know on my 50/35, the motor just kicks up. would hydraulic trim allow that without having to rebuild the seals?

 

[dhoganjr]

Trim holds it in place, it will not kick up like it does without trim. But with power trim the shoe is about 1" lower to level with the bottom of the boat on plane trimmed out, so normally it takes less hits.

Without trim it is usually 3 to 4 inches below the hull, so it is more prone to direct hits.

Most of the time on mine when I hear something start to hit the bottom of the boat I trim up more and throttle back a little if it starts to cavitate so it doesn't overrev, usually saves the shoe except for bent grates.

 

[smackdaddy53]

How much play should the shaft have left and right? I read with a stainless impeller you can go to within .015" but it feels like my shaft moves at least that much when I remove the foot and give it a little wiggle. Is this normal or did I somehow not install my bearing kit correctly? Looking at the mechanics of it there really should not be any play at all because the bearing is pressed on and the housing holds the bearing in place with four bolts. I am positive I installed the kit correctly and definitely have plenty of grease in the system because I shot some in twice already and it came out clean from the grease return hose.
I ran it on the hose this afternoon after I re shimmed and the tolerance is definitely where it needs to be but still had a little contact with the liner.
I hate to keep asking all these questions but I really thought this was going to be fairly cut and dried. Next step is to just put all shims on the nut side of the impeller and try it. I just bought this impeller and liner and I am not at all thrilled about ruining one liner already and scratching up the edges of my $380 stainless impeller. It just seems that if I remove all the shims from behind the impeller my leading edge impeller tolerance is going to be a hell of a lot more than .030".

 

[dhoganjr]

With a new impeller and liner most of the shims should be on the nut side to start with, all but about 1 or 2 usually. As the impeller and liner wear you move 1 or 2 to the top or inside of the impeller to move it closer to the liner to keep the tolerance correct. If I'm reading correctly you are starting with most of them on the wrong side.

 

[dhoganjr]

Here are some pic's to show the difference trim makes. This is trimmed down or tucked under.
https://i105.photobucket.com/albums/m219/dhoganjr/Mobile%20Uploads/2014-09/20140902_193011_zpsicioivuz.jpg

Here is trimmed out level where it runs on plane and will run trimmed past level.
https://i105.photobucket.com/albums/m219/dhoganjr/Mobile%20Uploads/2014-09/20140902_193229_zpscrrptgui.jpg

This is the shoe with about 21 hours on it, notice how the leading edge and front half have very few nicks and most all the paint left. Properly set any hits should occur on the grates or the rear half of the shoe.
https://i105.photobucket.com/albums/m219/dhoganjr/Mobile%20Uploads/2014-09/20140902_193444_zps8veu361k.jpg

 

[smackdaddy53]

With a new impeller and liner most of the shims should be on the nut side to start with, all but about 1 or 2 usually. As the impeller and liner wear you move 1 or 2 to the top or inside of the impeller to move it closer to the liner to keep the tolerance correct. If I'm reading correctly you are starting with most of them on the wrong side.

No, I had three shim washers on top (bearing side) of impeller and the spares on the bottom (nut side) and it was contacting tge liner so I moved one from top so it gave the impeller more clearance. As the liner wears common sense tells me I will move more shim washers to the top of the impeller to maintain proper clearance.
I am just wondering why my shaft is moving so much and if it is normal. There is at least 1/16" play left to right but none up and down. This tells me there is no way I can get .030" tolerance with that much movement.
I guess what I'm saying is I must be overthinking this and I should just not shim my impeller at all and go from there. Sound about right?

 

[Jetboater-TB]

A little looseness if normal before its all bolted up. This note is from OBJ's web troubleshooting web page: https://outboardjets.com/troubleshooting/

Driveshaft wobble in bearing housing before assembly

Before the driveshaft assembly is mounted in the motor, the driveshaft will appear to wobble in the bearings. This is a normal condition. When mounted in the motor, the upper end of the driveshaft is supported in the crankshaft and the system becomes quite rigid under load. If you are concerned about the condition of the bearings, watch the texture of the grease coming out of the lube hose during lubrication. The 630-AA Lubriplate grease coming out will normally be light gray. If water is present, the seals need to be replaced. If the grease starts turning dark gray, the bearing should be inspected and replaced if necessary.

 

[dhoganjr]

smackdaddy53 » 02 Sep 2014, 20:52[/url]"]

With a new impeller and liner most of the shims should be on the nut side to start with, all but about 1 or 2 usually. As the impeller and liner wear you move 1 or 2 to the top or inside of the impeller to move it closer to the liner to keep the tolerance correct. If I'm reading correctly you are starting with most of them on the wrong side.

No, I had three shim washers on top (bearing side) of impeller and the spares on the bottom (nut side) and it was contacting tge liner so I moved one from top so it gave the impeller more clearance. As the liner wears common sense tells me I will move more shim washers to the top of the impeller to maintain proper clearance.
I am just wondering why my shaft is moving so much and if it is normal. There is at least 1/16" play left to right but none up and down. This tells me there is no way I can get .030" tolerance with that much movement.
I guess what I'm saying is I must be overthinking this and I should just not shim my impeller at all and go from there. Sound about right?

From your earlier post just wanted to make sure they were on the correct side. If it is rubbing any at all out of water it will flex a bit under load and rub more in the water. Try them all on the nut side and see where you are. Unless the bearings are not completely seated or you have a bent shaft everything should line up correctly. You said the bearings were installed correctly so I would rule that out.

About the play in the shaft, I don't think mine has any play. Did you get a new Teflon or plastic sleeve with the impeller, goes between impeller and shaft and has a slot for the key to fit in.

Hope I am helping you, I know it is frustrating when things aren't working correctly.