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Cracked anti-cav plate
gusgus	#1  Posted on 01/11/12 - 11:39 AM
Member Personal Page Posts: 233 Comments: 3 Joined: 10/12/11	I have a 1987 Merc 150 and the anti cavitation plate is cracked. I found the crack along the left side. aft end of the horizontal wings just above the propellor, but it traverses closely along the left side of the tower. The crack ends by turning away from the tower (main vertical body) and ends about an inch from the body. the entire crack is about 6 inches long. It is tight and aligned with the base material. How would you all suggest I deal with it? Weld? Doubler riveted? 1987 Outrage 18 W/150 Merc and 8 Honda
Phil T	#2  Posted on 01/11/12 - 2:18 PM
Administrator Personal Page Personal Album Project Albums Posts: 7043 Comments: 6 Joined: 03/26/05	Please post a photo showing the crack in detail. 1992 Outrage 17 I 2019 E-TEC 90, Viper 17 2+ 2018 Load Rite Elite 18280096VT
tedious	#3  Posted on 01/11/12 - 2:46 PM
Member Personal Page Posts: 1072 Comments: 2 Joined: 09/07/08	Clearly we'd be able to give better advice with a picture, but my inclination would be to: - drill a 1/8" hole at the very end of the crack to keep it from growing - fabricate a reinforcing plate from 316 stainless to "bridge" the crack - may need more than one depending on the crack dimensions and shape - mount the bridge (or bridges) on the top side of the plate, using 316 SS machine screws with the screw heads on the underside (and washers there too) - try to mount the bridges so they pull the crack closed, if it's displaced (do this as a dry mount first) - fill the crack and the drilled hole with JBweld, then do the final mount on the bridges to pull it all together - sand and paint if you care - go boating
Tom W Clark	#4  Posted on 01/11/12 - 2:50 PM
Member Personal Page Posts: 4280 Comments: 7 Joined: 09/30/05	There are a number of ways to fix the problem but on a 25 year old two stroke, I would not bother. Leave it be. Even if it breaks off, it is not going to affect performance significantly. If you are set on doing anything, the easiest and cheapest would probably to buy a used gearcase and swap it out in its entirety. A good used gearcase for the 25" shaft Mercury 150 can be had for $600 or less. It would cost that much to pull the existing gearcase, pull the gears set out, weld the gearcase, reinstall the gears, shim, seal and reinstall. It's just not worth it on a motor that *might* be worth $1500.
fishrswim	#5  Posted on 01/11/12 - 4:58 PM
Member Posts: 168 Comments: 7 Joined: 05/25/11	If you do decide to leave it, I'd at least drill the stop holes at each end. Is there enough material left to just cut it off and attach an aftermarket hydrofoil cavitation plate? I'm looking at my West Marine catalog and some versions don't require drilling any holes. Even better, they're cheap. I confess, I've never used one, but I see them all the time, so somebody must like them.
Bake	#6  Posted on 01/11/12 - 5:45 PM
Member Personal Page Project Albums Posts: 902 Comments: 8 Joined: 01/30/06	grind or file it out a little and use j b weld. sand smooth and paint
Doug V	#7  Posted on 01/11/12 - 7:37 PM
Member Personal Page Posts: 340 Comments: 3 Joined: 09/21/05	I had the anti cavitation plate of my old Suzuki 200 welded. I used it for several years after with no ill effects. If I remember correctly, I did change the gear case lube after the weld job. Doug
CES	#8  Posted on 01/12/12 - 3:55 AM
Member Personal Page Photo Albums Project Albums Posts: 2681 Comments: 7 Joined: 04/27/07	Cav plates break all the time and are easily repaired. Bring it to a prop shop and they should be able to weld to where you cannot notice where is was broken. Cliff 1966 13' Sport with a 1993 40hp Yamaha 2 Smoker
mtown	#9  Posted on 01/13/12 - 1:10 PM
Member Personal Page Posts: 613 Comments: 5 Joined: 07/06/08	My 1985 70hp yamaha had a similar split in the hub surrounding the prop. The aluminum was starting to peal away and I wanted to keep it from getting worse. No marine shop would touch it, so I went to my auto mechanic, who is also a good welder. He broke the piece off where it wanted to break and heli-arced sp? it back in place. We removed the prop but nothing else [there is rubber at the hub/prop mount and the gears nearby]. I ran the motor for at least 5 more years and sold running fine when I re-powered last year. So; I say weld it.
JohnnyCW	#10  Posted on 01/13/12 - 3:45 PM
Member Posts: 684 Comments: 0 Joined: 08/16/09	I got a crack in my old 1991 Mercury 115 back around 1998. Fortunately I have some welding experience and the equipment so I TIG welded it myself. I ground down the repair, primed and painted. Until the day I re-powered with an E-Tec a couple years ago, the repair held and could not be detected with the casual eye. Edited by Tom W Clark on 01/14/12 - 7:13 AM
jimmyrinaldi	#11  Posted on 01/13/12 - 4:57 PM
Member Posts: 212 Comments: 3 Joined: 11/29/07	Are you insured? If so, and the shop deems it a strike crack, it is covered. Edited by Tom W Clark on 01/14/12 - 7:11 AM
gusgus	#12  Posted on 03/18/12 - 11:53 PM
Member Personal Page Posts: 233 Comments: 3 Joined: 10/12/11	Tracking threads is not easy. I lost this one for sometime it seems. Thanks for all the advise. I haven't had it repaired yet but I am in the middle of a refit of electronics and a battery location move. But I am going to have a boat shop have a go at it soon. Thanks again everyone. 1987 Outrage 18 W/150 Merc and 8 Honda