Problems With Mercruiser Limiter Blocks
Several boat owners have had significant, expensive damage caused to their
caused by Limiter Blocks that were installed on the outdrives.
Following is some information and photos to help you determine if your Mercruiser Outdrive
has the Limiter Blocks, and what you may do to prevent damage to your outdrive.
If you have any information or photos relating to this problem that you would like to share here
please email me at email@example.com
Mercruiser Service Bulletins
Outdrive without Limiter Blocks
Bob G The trim-in limiter blocks were used on 1997 1/2 and earlier Bravo 3 outdrives. If you have two groves in the top of your bell housing you DO NOT have the limiter blocks. ( these indentations on the bell housing are to provide clearance for the U-bolt nuts).. If you do not have the indentations (and you have a Bravo 3) then you probably have the trim-in limiter blocks. Raise the outdrive and look just to the rear of the mercathode system and you will see two metal blocks 2" X 2" X 1". You can wiggle them around with a finger. If you see them , then you have limiter blocks. Don't make the mistake of replacing the lower half of the outdrive with the newer design without giving attention to the bell housing or the first time you trim all the way up to trailer the boat, the U-bolt nuts will come in contact with the bell housing (since the outdrive will be coming up higher) and you could crack the bell housing. My outdrive was under warranty when it cracked so mercruised sent me a new lower unit but forgot to mention the bell housing (which should have also been replaced under the warranty) so instead of pulling the bell housing I just drilled about an eigth of an inch out the two contact points. If you outdrive is not cracked and you do have the trim-in limiter blocks I would certainly recommend getting rid of them and then just put some limit spacers in the trim cylinders (easier and cheaper than replacing the lower unit). It would be dangerous to just pull the limiters out because with the Bravo 3 trimmed all the way down, at high speed, the rear end comes up you then get Bow steer and you could loose control of the boat. I have never taken trim cylinders apart but I am told it requires special tools and is a big job so is probably best left to a reputable dealer.
Outdrive with Limiter Blocks removed
Jim P My B3's top cavitation plate had severely cracked. I thought I had hit something, but after seeing my chewed up trim limiting blocks, knew I didn't. I did a ton of research on the web and finally, I found the original Merc service bulletin about these blocks. If memory serves correctly, they started using them around 1994, a year after the B3 came out. My 225 is a '95. I think the bulletin said if you took a turn at high speed without the blocks, you could lose control of the boat, like flipping it over. I never do that anyway - I've always got the trim 1/4+ out. Again, if memory serves correctly, they (Merc) discovered later on these blocks could rotate and crack the plate, so they went with different trim cylinders. I think I read that part in a service manual somewhere. In my situation, I welded my drive back up, painted it and it has been fine. I discarded my blocks and found that the additional 3/4" inward travel made my boat plane like I put a hydrofoil on it. I love this accidental find on my 225. The 266 being a longer boat may not like such a change. I don't recommend anybody doing what I did because I don't want to be responsible for someone getting hurt. I would like to add this applied to ALL manufacturers utilizing the Bravo 3 at that time. My buddy has a '98 Chaparral with a B3 he bought new. He doesn't have these blocks, just different trim cylinders/slots and has never had a problem. I hope this helps some of you looking for a time period these blocks were put into use. They are easily identifiable - they are aluminum blocks, literally. They are about 2" wide and an inch or so thick. They are on the fore, horizontal trim rod, close to the bilge plug. You have to lay on your back to see them. Here are some pics of where they were. I've had a few people email me about their location so I thought I'd share what happened to me. Like I said above, I threw my blocks away, so I don't have pictures of them. But they used to reside on this forward trim cylinder pin, right in the middle. If you look closely, you can see where when they spun around and took a chunk out of the upper part of my Mercathode reference unit. (Broken plastic) You can also see where they chewed up my lower swivel pin housing just above the pin. The next pic is exactly where my cavitation plate cracked. Luckily it didn't break completely off, but it was raised up 1/8" at the crack. It took a lot of work to fix it. It also bent the sacrificial anode too, which is still slightly bent upward.
Outdrive with Limiter Blocks installed
Outdrive Damaged by limiter blocks
Greg, Attached is a picture looking aft showing the damage caused by the limiter blocks on my 97 225BR. As you can see, the entire front portion of the cavitation plate is completely gone. In the picture, the trim actuators and one limiter block are removed as I had disassembled the area to try to figure out what was going on. The Mercathode unit is also damaged. Initially, I assumed the previous owner had hit something with the drive, but on inspection, I could see the corners of the stop blocks were worn allowing them to rotate nearly freely. Also attached is a photo of the most worn limter block that showns the wear that allows the block to rotate. The sad part of this issue is, I purchased the boat in this manner. Had this issue been more publicized, it might have been found during pre-purchase. Until I noticed the information on the Crownline site, I assumed my issue was isolated. Although I have not repaired it yet, I am quite disappointed that this issue was not identified and corrected on all such drives, within the drives warranty period, as it is obviously a design defect. Tim F