How to Remove and Replace Your Sailboat Engine

[Obi Wan]

Here are some tips and lessons I learned from removing and reinstalling my Universal 5424, O-Day 34, which I recently finished. Putting this out as a sort-of checklist to hopefully help someone else considering it.

- Before you do anything, take lots of pictures – and video too. If you think one picture of a particular view is enough, take 10 slightly different ones, with good light. Videos are good too because they show things you don’t necessarily see in the pictures. If you think you will remember where something goes, you’re wrong.
- Buy a chain hoist. They’re not that expensive. It’s worth it if you only use it for one engine change. Get a one-ton for most small engines, consider a two-ton for the bigger ones to have a margin of safety (the Chinese tend to overstate the ratings). A come-along will work, but not well. A block and tackle will work, but not well. A chain hoist is safe, easily reversible, and handy. I would even consider taking one with me on extended trips (just in case).
- Drain the fluids as much as you can.
- As you disconnect and remove, label everything. If a wire disconnects from a terminal somewhere, use tape and mark the wire and what it came off of. Take pictures of the label on the engine part (in context) before you send the engine off or do the overhaul yourself because that label will disappear.
- As you remove hardware, place everything in marked baggies, or jars, or boxes, or something. Those little plastic tubs lunchmeat comes in work great. Start hoarding them 6 months prior. Again, if you think you will remember where something goes, you’re wrong.
- Build a compact cradle out of wood to fasten your engine to as soon as you remove it from the boat mounting rails. This will make your job safer and easier and help protect your boat.
- Measure the height of each of your engine mounts and mark them down somewhere. Draw an outline of where the mounts are. This is so you can get them back pretty close to where they were to minimize your efforts for re-alignment.
- Bring your boat right up next to the dock and tie it off. Tie a rope from a piling DOWN to the boat deck to keep the boat from rolling as the weight of the engine is swung over to the dock.
- Run your main halyard to the boom at a point above the companionway (CW) and wrap it around several times to tie it off. Use a good-quality webbing strap (rated at least double the weight of your engine) and wrap it around your boom several times right above the CW closest to the engine. Hang your chain hoist from this strap. Raise your boom to a height above the CW entrance floor equal to the height of the engine (in the cradle) plus your engine strap/chain, plus the distance the hoist and hang strap take up when the hoist is at the fully raised position, plus a foot (it will sag).
- Leave the engine mounts on the engine and remove the hardware holding the mounts to the rails. This will facilitate sliding the engine forward and allow you to fasten the mounts to the cradle you built. In my case the front bolts were built into the mounting rail (a single front and center mount) but I was able to lift the front of the engine up so that the mount cleared the bolts.
- Connect your hoist to your engine and start hoisting. This will pull it forward along the mounting rails. Rest the front of the engine on your wooden cradle or another piece of wood with the back mounts still on the front of the rails. This will allow you to shift your hang strap on the boom a little more forward. You will want the hoist at a spot where you have to pull the engine forward a little to clear the CW, and then back a little to get it through the CW. Hoist the engine completely out of the bay, and set it in your cradle on the floor of the boat.
- If you haven’t already done so, remove the transmission at this point. You should be able to raise the engine up and swing it around so the transmission is to the front, making it easier to remove. It will make clearing the CW much easier. I couldn’t get mine off (severely corroded bolt) and I was still able to get it out that way – I just had the neighbor come over and pull on a rope to clear the CW, although I really could have done it without him.
- Hoist the engine. NEVER get underneath it. Pull it forward to clear the CW, and once above the deck, change your position to the deck. Then pull the engine back as you lower to rest the engine/cradle on the deck, just outside the CW (part of the engine can still protrude into the CW – just make sure it’s not going to fall back in. I used a hardy rope to tie it off just in case). You also may need to re-inforce your deck with some sturdy lumber if you think your deck can’t take the weight. Chances are it will. Another option is to place some sturdy lumber across the seats to rest the engine on, but make sure you take this extra height into consideration.
- Let your hoist out and raise the boom some more. The purpose of this is because your hoist travel distance may not have been enough to bring the engine all the way from the cabin floor to a height that will clear the sides of the boat. If your hoist is long enough, just have the boom at a height to begin with that will give you the necessary clearance.
- Measure from your mast to the spot on your dock where you need to set the engine. Hopefully it’s close to the distance from the mast to where your engine is sitting in the CW. It may be a little more. Shift your hang strap back on the boom to the necessary spot you just measured. If it’s a big distance back, shift your halyard back too.
- Make sure your mainsheet is let out enough that the boom will swing as far over as needed. You may need to release it form its shackle.
- Hoist the engine again and carefully swing it out over the dock. If you have others around and haven’t tied your boat well, have them counterbalance the weight on the other side of the boat.
- Congratulations, it’s not that hard to do!
REINSTALLING
- For getting the engine back in the boat, pretty much all of the above, in reverse.
Additionally:
- Buy new engine mounts if your old ones were corroded. The rubber goes bad too.
- Splurge a little and buy some stainless steel hardware to replace those rusted bolts. The next person to remove the engine or work on it will thank you (and it may well be you).
- Accomplish all those things not easily done with the engine installed – replace your fuel tubing, clean out the water separator, clean the engine bay, etc. Consider replacing your bearing box packing and hose, especially if you are on the hard. It’s a whole lot easier without the engine there!
- Set your engine mounts to the height they were before you removed the engine (and the left and right should be pretty close to even). I installed a new and different transmission so had to add the additional drop to the height of the engine mounts (1 cm in my case).
- Find the center of your prop shaft travel by grabbing it and gently moving around in a circle. The ideal position for alignment is going to be pretty close to the center of that circle. Use pieces of wood to prop/wedge/clamp it into position. A woodworker’s parallel clamp works well for this too.
- Once you have lowered the engine back on to the rails, it should slide back into position (with some persuasion) as you continue to lower the hoist.
- Reinstall the engine mounting bolts to the rails. Don’t tighten just yet.
- Check the alignment of the shaft plates. They should be close to being parallel. If way off, adjust the up-and-down mounting nuts and slide the engine around to get them close. Once they look close to parallel, the next step is to get the two plates precisely aligned left and right, with the distance between the two equal at the 3 and 9 o’clock position. If the left and right edges are even, but there is more space on the left side than the right, then you have to shift the front of the engine to the left. Of course, you will still have to shift the back of the engine slightly too, because it will pivot about the aft engine mounts and throw the edges out of alignment. Do this repeatedly, until the edges of the plates are even, and the distance between the two plates at the 3 and 9 o’clock positions are exactly parallel (or at least pretty darn close - use feeler gauges or a dial caliper - I’ve heard .001” is the tolerance).
- Once the left/right alignment is good, snug down the engine mounting bolts. Now check the L/R alignment again. It will be off. When you tighten the bolts, it will mess up your alignment that you worked so painfully at getting just perfect. Repeat above process again (and again).
- Once the left and right alignment is good, AND the mounting bolts are tight, work on getting the up and down alignment. So, if the top and bottom edges are even, but there is a wider gap at the top, then you raise the front of the engine. Again, you will also have to raise the back mounting nuts a smaller amount than the front to keep the edges aligned. You can even calculate it out – a direct ratio. If the rear mounts are halfway between the front mount and the drive plates, than the distance you change the aft mounts is half the amount you change the front mount(s). Repeat and fine-tune until the space at the top and bottom of the plates are exactly equal. Plan on this whole alignment process taking a while unless you are really lucky or good.
- Cuss at the sailboat builders whose designs require you to crawl back into tight spaces on your side and repeatedly contort your body into uncomfortable positons to accomplish simple maintenance tasks on the engine. Ask God why he didn’t bless you with a third arm. Be prepared to have a sore hip and shoulder for days. (The best design I ever saw was a Hunter 33 with an aft side cabin that allowed the engine to be completely exposed to be worked on).
- Now your plates should be perfectly aligned. Bolt together.
- The rest is easy.
- Re-connect all those wires you marked well.
- Reconnect fuel lines and bleed
- Re-install/replace hoses with new if it’s been a while.
- Re-connect control cables. Take extra care to get shifter cable adjustment correctly so you get the full throw.
- Add oil/coolant/transmission fluid.
- Crank it up and go!
I did it all myself, so it’s possible to do alone, and not really that difficult. Every boat owner should consider this – you become intimately familiar with your engine and its surroundings and will have a much better understanding of your systems and confidence that you can fix most anything if need be.

[Steadman Uhlich]

Outstanding post!
Thanks for sharing the detailed description of your project.
I am sure your notes will help others.

[artisthos]

Will be following your instructions. Thank you for the post.





Re-power from a hydraulic pump. The new engine is 3YM30AE with KM2P 2.62:1. The rail distance on the new engine is 8" shorter. My challenge is to make rail extensions. Making a 1/4 wood dummy for the machine shop to follow. Would you bend 1/4" plate?
Also the jig will be at the bottom of the mounts instead of at the top as it shows in the Yanmar installation manual image. I will not put the mounts on the jig. The jig will be made out of 1/8" aluminum. The flaps for the center-line will go up instead of down.

[artisthos]

The images:

https://www.flickr.com/photos/434903...posted-public/

https://www.flickr.com/photos/434903...posted-public/

Thank you ahead of time for any insight. Click Here for Beer.

[gonesail]

i would recommend 2 halyards if possible .. connected to the same point on the boom as the hoist (or block and tackle) is. even for something like a big battery.

[Obi Wan]

Originally Posted by gonesail

i would recommend 2 halyards if possible .. connected to the same point on the boom as the hoist (or block and tackle) is. even for something like a big battery.

A ½ nylon rope has a breaking strength of 25 kN. Two halyards are not necessary for lifting a 450 pound engine.

[er9]

Wow! great info. thanks for taking the time.

[zboss]

Good write up. I’ve gone through the same recently.

Not having to modify your beds are one of the best reasons to go with beta marine vs. yanmar. For $800 beta marine will make custom mounts for any variation needed as long as you can provide the measurements. For cruisers not doing all the work themselves or that don’t want to do a lot of modifications to the boat, this is a great and affordable option.

[RaymondR]

On my last boat I mounted the engine mounts on angle iron dummy rails which greatly facilitated sliding it forward and allowed the engine to be removed and replaced without disturbing the alignment.

[artisthos]

https://youtu.be/dLIhW_VhmE4
Engine removal video. Things went so well I almost wore myself out. Turns out the prop shop had one in stock so there is nothing stopping use but my old age.
Installing Cape Horn self steering next.