if you are replacing the water hose buy the water insert tool its only a few $$ makes get the plastic inserts easy to screw in .

Is there a trick to getting the shaft seal out. Doesn't seem like there is a lot of room to hit it and distort the seal to get out. The machined area this seal sits is almost as big around as the seal?

I did get the gimbal brg out, it was stuck in there pretty good however

For what it's worth, I installed 18-2100 in a 1995 bravo III and it seemed to have a little more u-joint knock at the extremes than before the install. This could be for any number for reasons, but I figured I'd add my experience to the thread. I'm going with 18-21005 for my alpha gen II this weekend.

Hi there,
Hoping BUP or somebody that knows sees this question - BUP said:

"Next 1998 and up Merc takes GB 18- 21005 and do not put this one in backwards - the inner portion end is a tad shorter on the end - it shaved down compared to the older GB - I think around .030 This needs to be facing out when you install it. Both of these GB are greaseable"


I have a 1999 Capri boat with an Alpha One Gen II and while I was away on a trip, my dad (a very good trained mechanic, but not a boat mechanic) thought he would help me out and put a new gimbal bearing (Sierra18- 21005) in for me. I had already purchased it, and we were gonna do the bellows, shift cable, and gimbal bearing install after I got back from the trip. When I got home last night, he had already installed the gimbal bearing. [B] He installed it with the two slots facing inward[ toward the boat/B]. This is the way the service manual says to do it, so he just followed the instructions.
My questions is...is that the proper way? Or are the slots supposed to face outward toward the back? I have searched the web and seen two different opinions about this. So now I am wondering if we need to pull it out. I really appreciate any help you are willing to give.

Sincerely, Willy

Yes I am up here today and see your post brought all this back up. Hey NOT to knock anyone up here but do not install 18-2100 GB in 1998 and newer boats. Sorry guys you are 100 % wrong and do not know the reason. For one I have the SB's from the bearing makers GKN and SKF along with Mercruiser. But I know some will come up and say it works no problem - ok great for now but I guess the companies that make these GB's have no idea and the end user knows way much more than they do.

Anyways what do you need to know.

next all sterndrive manu's went away from a greasable GB. For many reasons. One is the end uyser never greases them anyways. Next water intrusion is a somewhat better for not locking up the bearing up in short order from corrosion. Next many techs and do it yourselfes sometimes have problems lining up the grease holes so when the zerk is greased the bearing internally is not getting greased. The average is the non greasable GB has a longer life in use. Volvo Penta has used a NON Greasabl GB since the latter part of 2006 model year 2007. I have changed less of them in the past 9 years than the greasable ones that are 9 years old - regardless. If I would have to count how many GB I have changed out it at least 1500 if not more maybe 2000 GB's. Just saying. Current bearings use by the manu's are SKF and GKN.

A 3 jaw puller is waste of time - the newer tools on the market pull these bearings in your sleep.

As I noted above, He installed the Sierra 18- 21005 greasable gimbal bearing. Everything is lined up well. But the question I posted above is concerning the fact that he installed it with the two slots facing inward. I keep seeing different opinions about this and am wondering if he installed it backwards or not? Basic question is...Do the two slots face the front of the boat or the back? Service manual seems to indicate the slots go inward toward the boat.

Sorry I finally just seen your PM. I wonder how you were able to get one in. They are full.

Anyways - yes slots need to face inwards, These really are called bearing carrier notches just an FYI.

Thanks so much for your advice. I guess the message got through because I sent it the other way, But the reason I am confused about the install of what direction the bearing carrier notches go is because the Sierra dealer I bought the bearing from is telling me that (His words) "Yes! take it back out, If you leave it that way with the notches facing inward, you will not get proper alignment and blow out a coupler on back of engine. The bearings are slightly tapered inside and outside. You may have a real hard time removing the bearing now because it is wedged in. Do not look at Utube videos or the manual they are backwards. We rebuild hundreds every year."

Those were his words above - So is he just completely misinformed?

it makes no difference either way ..if you put it in with notches facing toward you ..the bearing in the center can be turned to the side and pulled out .that's what the notches are for .I had a bearing place up here that sold just the center bearing only .I have replaced hundreds of these bearings with never an issue

Got to jump in for the last time. Again the newer GB for all 1998 apps and above has it reasons for the change & part # change plus the proper way of installment.

The newer GB on one side ( the center portion center inner race) is .090 shorter in length compared to the other side - this side needs to face out towards the drive. Again one more time it is .090 shorter than the other side of the GB. It is shaved .090 shorter for clearance purposes is the main reason.


Also in 2004 Mercruser had to changed to GKN U-Joint / input shaft assemblies that replaced the Rockwell U-Joint assemblies (NLA) from Rockwall ( I am talking about on the outdrive side here) - These newer assemblies caused interference with that center section of the GB. This also put extra load on the GB. A new bearing was offer that is shaved .090 off compared to the other side. The reason for the new GB and for the shorter side facing outward when installed.

NOW IF YOU HAVE 1997 and BACK APP that still has OEM stock Rockwall U-joint assemblies the 18-2100 will work and can be installed either way.

Next the GKN U-Joint assemblies come black in color the older Rockwall U-Joint assemblies came in non painted grey in color. FYI

Can someone post Mercruiser Service Bulletin 2000-8 up - if I recall that might be the SB that started all of this way back in year 2000 but could be WRONG about the SB #..

If I recall this the first start change of the GB because Some complaints came in from Bravo users of slight noise .Merc followed up and put out Service Bulletin about the change GB for Bravo apps at that timeframe. Then later on came into play for the Alpha apps.

Again this applies to Mercruiser 1998 and above assemblies as they Merc - DECIDED to have this newer GB to be used way back starting 1998 till the grease Jerk was completely removed in 2008..

All current Merc assemblies since 2008 use a non greasable GB and still is installed with the shorter side facing out. Merc does not even sell a greasable GB if I recall correctly. They want you to install the newer one Non greaseable GB then remove the grease jerk and replace it with a plug retrofit.. Good Luck.