Removing Lower Unit '58 Mark 30E

I just purchased a boat that came with a '58 Mercury Mark 30E. I'm trying to clean out the old grease and replace the water pump impeller. I've checked the manual, which says that to remove the lower unit, you need to pull one central 9/16 nut from the bottom, and the two smaller side nuts from the top. I've done this, and there's no bolt in the exhaust port or anywhere else I can find, but the lower unit won't separate from the engine. The prop is still attached, as is the power unit. Is there something else I need to remove?<br /><br />Thanks.

Re: Removing Lower Unit '58 Mark 30E

The bolt in the exhaust is a 5/16th allen head, if you can see a empty hole there some one forgot it and the unit should come down if you don't find the empty hole keep looking if you do use a little persuasion

Re: Removing Lower Unit '58 Mark 30E

thanks.<br /><br />No bolt in the exhaust. I ended up using a wedge between the halves. Turns out the drive shaft was rusted into the flywheel. It did come out though. Now I'm just stuck with a cracked/bent anti-cavitation plate and a water pump fixing nut that won't budge at all. I'm pouring on the penetrating oil and taking my time. Has anyone succeeded in getting that nut off without the special Mercury tool?

Re: Removing Lower Unit '58 Mark 30E

Hi Cheburashka,<br /> You ought to be able to make a fair approximation of the WP cover removal tool using a pipe coupler. A friend of mine made one using a heavy pipe "T" and then grinding down one end of the fitting to give it four nubs to seat in the WP cover. He then used a large screwdriver in the side of the "T" to act as a handle to open the cover. <br />Something like this:<br />| |<br />| |___<br />| ___ - Screwdriver goes here.<br />| |<br />| |<br /> <br /> | Driveshaft goes here. Grind this end to fit cap. <br /><br />Pipe fitting diameter should be about the same as the cover with enough meat on it to give you a solid fit. Something cast - look for a threaded fitting.<br /><br />Good luck! Be sure to grease the splines of the driveshaft to prevent it from rusting again...<br /><br />One other word of advice on the Mark 30s. If it came with a bronze prop - shine it up and hang it on your mantle. Find an aluminum prop for the motor, something that allows the motor to reach about 5800 revs at WOT. The Mark 30 units aren't very robust (basically the old Mark 20 unit with a heavier driveshaft) and won't take a beating, particularly when shifting. The lighter aluminum props help save the clutch and gears. Also, if you're seeing evidence of water intrusion, consider resealing the unit.<br /><br />- Scott

Re: Removing Lower Unit '58 Mark 30E

Thanks for the advice, Scott. I guess as long as I have it apart for the impeller (which was shot,) I might as well reseal and look for a better prop. Could you recommend a good size and pitch? The motor is on a Glasspar G3.

Re: Removing Lower Unit '58 Mark 30E

Hi Cheburashka,<br /> For a small boat, the G3s aren't generally very light, which is why you see a lot of them with larger motors on them. Might want to keep the pitch conservative at around 11-12. Won't really know until you try it. If it's really slow out of the hole, find a leaner prop. If it's real quick out of the hole and the engine sounds like it's screaming it's guts out, then go a little taller on the prop. It never hurts to have a few spares anyway, and you can find good used ones on eBay all the time. Be careful not to run a small Mark 20 or Mark 25 prop on it, as the blade area will be a bit smaller. Make sure it's a Mark 30 prop....<br /><br />- Scott