52 merc rocket motor questions

[sundancekid]

Just recently picked up a 52 mercury rocket 7.5 hp motor. It's been sitting in a garage for at least 5 years. I got it with a boat and trailer combo from a friend. I'm a weekend mechanic but don't know much about outboard motors. I'm assuming that it's a direct drive because I don't see anyway of engaging a drive gear. So with that in mind when I pull the cord to turn it over it's a little stiff to pull. Is this because it's trying to turn the lower drive uint at the same time or something else. Should it turn over as easy as lawnmower? I've pulled the plugs and did the whole finger over the hole and it feels like it has some compresion but don't know how much. I'll be putting a comp gauge on it on my next days off to get a good reading. Does anyone know what kind of numbers I should get? Next is the fuel system. It's gunked up pretty good. I'll replace the lines and inline filter and take the carb apart to clean it but how should I go about cleaning and flushing the tank? Is there a good solvent I can use? I guess I need to ask if these are worth putting any money into or should I look for another motor? The boat I got with it is a 1960 14' crestliner that I want to use for fishing and tooling around the lakes/ponds. Any and all help is needed. Thanks Dave

 

[Chinewalker]

Re: 52 merc rocket motor questions

Hi Dave,
The Rocket is a good little motor - in both its incarnations (Model KE4 and model Mark 7). I've got a couple of them in my stable of old Mercs. Very spunky for a 7.5!
The nature of the recoil type makes them pull over relatively hard, compared to some other motors. Also, they make decent compression for a small motor. My 7.5s will both nudge the needle into triple digits on my gauge. That doesn't mean yours couldn't benefit from a squirt or two of oil in the cylinders and carb intake to loosen things up inside. If it makes any odd bearing noises from the powerhead, it may need a partial teardown to inspect.
You are correct in surmising that it is a direct drive. Check the gearcase lube - it takes grease, not oil. I use Lubriplate 105 in mine.
For ignition parts, waterpump impeller, carb kit, etc. get familiar with oldmercs.com - they have pretty much everything you need to get your motor going again!
- Scott

 

[sundancekid]

Re: 52 merc rocket motor questions

Thanks for the info it was a great help. Dave

 

[MSZ]

Re: 52 merc rocket motor questions

I'm building a KE4 at the moment.

vintageoutboard.com has a better carb kit. Get one. Check for spark before you go any further and R&R as necessary.

Change the water pump.

I'd start by getting a service manual and learn about the motor before you do anything else. They are pretty simple to fix if you understand the steps needed to fix things.

1. Check for compression and spark.
2. Clean out the carb and if the cork float is still in there, coat with dope (model airplane dope, do a google search)
3. Change the water impeller
4. Clean out the tank after you remove the intank filter

read the forums at www.aomci.org and http://www.pfs-ware.com/phpBB3/index.php

You may have to replace the upper and lower crank seals. If you lower unit has water in in when you are adding the 105, you may want to replace the lower unit seals as well.