My first motor

[SteveinVA]

Ok hello all, was hoping someone could give me some guidance.
I got a donor 6hp Johnson. model # CD25R. Ser # J2909879 first off can anyone tell me what year that might be? Is it a 79? read somewhere the last two digits is the year.
So here whats happened so far. Got the motor cleaned it up with out taking it apart. checked the spark plugs, sprayed a lil starting fluid in and it fired right up. shifts fine and all. Took it out once without any problems, just running a lil rough (sputters ocasionally when cruising)and doesnt go fast at all. didn't get my boat on plane. I am using it on my 12ft fiberglass V hull. boat probably weighs around 650lbs total with 2 people in it. Should this motor get me on plane? Ok next trip out. motor starts up and gets us on are way. then stalls out probably 5 mins later and wont restart. pull the cover and after a few pulls starts running again, put cover on runs for a few seconds then stalls and wont restart. take cover off starts and I decide to ride with cover off. So we are cruising along and RPMS start to drop until it dies. I try the pull cord and the motor wont turn. So head back to dock with troller. Next day pull cover and break motor loose turning the big round thing on top( dont know what its called). decide to check compression and I have 50 psi on each cylinder, is that good????
Decide to pull the lower unit to check impeller and I can turn the impeller by hand on the shaft without the shaft spinning. UH OH pretty sure that is bad. the pin that goes in the shaft appears to have worn a groove around the entire inside of the impeller. As it stands now I have ordered a new impeller kit from here, and cleaned out the impeller housing and lower ger unit. Anything else I should give a look before I reassemble and try to start.
Thanks in advance for any advice I really appreciate it

 

[oldcatamount]

Re: My first motor

She quit on ya because she got hot. You're doing the right thing by replacing the impeller. Because it got hot, it may now have a blown head gasket and that would be the reason for the low compression. Neither of these issues are terribly expensive and in my opinion, the motor is worth the time and effort. I would suggest, however, that you not put any more money in it until you have replaced the impeller and the head gasket. If that brings the compression back up, and keeps her cool, then you might consider a tune-up and a carb kit. As far as the year, I'm not in the shop and don't have the book with me but someone here will answer that question.

 

[kbait]

Re: My first motor

1968. 50/1 fuel/oil mix.

 

[SteveinVA]

Re: My first motor

Awesome thanks for the reply, any idea what compression PSI this motor should be at. I have worked on motorcycle engines before, and the main thing for the one I worked on was not the compression # nessecarily but that all the cylinders had the same reading or were very close.
Dont know two much about two strokes, do the pistons have rings? I am guessing the do? Should I be woried about them
thanks again

 

[SteveinVA]

Re: My first motor

thanks kbait

 

[Xcusme]

Re: My first motor

Nope, don't worry about the rings ..you're on the right path with the impeller. Get her running cooler then you can see what else she needs.
Post back with you're findings.

 

[kfa4303]

Re: My first motor

Hi SteveinVa. to answer a few of your basic questions;

6 hp probably won't get you up on plane unless you've got the weight distributed just right, but it's hard to say for sure. every boat is unique. unless you've seen it get that particular boat on plane before, don't be surprised if it doesn't, but that's ok. you can still have plenty of fun with it.

"big round thing on top" is a flywheel (a.k.a. harmonic balancer) and has many functions on the motor. it is used by the pull starter to turn over the motor. it also helps to smooth out the overall rotation of the enginge. it has a tapered, conical hole which sets on to the tapered head of the cam shaft and is held in place in friction and a single flywheel nut. it can/must be remove with a special, but inexpensive tool, called a harmonic balaner puller, should you need to do any ignition work on the engine such as replacing the points, coils, or condensers. if the motors runs too hot for too long some of these elecetronic bits may be damaged, but they are fairly cheap and easy to fix, should you need to. the flywheel also has a magnet on its underside along the edge which passes very near the face of the two ignition coils under it. the magnet induces and electric field which is ultimately sent ot the spark plugs to fire the cylinders.

50 psi in each cylinder may be a bit low, but as you say it is more improtant that they be within 10% of each other. you should also try to check the comp when the motor is warmed up, if possible.

2 strokes do have rings, but don't worry about that for now. you're on the right track with the impeller. get that fixed and cooling the engine and take it from there. once she's running and pumping water well, there are a few simple things you can do do help improve the compression if need be.

Good luck. Keep us posted.

 

[cajuncook1]

Re: My first motor

Here, check this link...its a good read. You should consider getting a service manual for your motor.

http://www.sschapterpsa.com/ramblings/OMC_6hp.htm

Good luck I hope you get her up and going again!!

 

[cajuncook1]

Re: My first motor

Ok hello all, was hoping someone could give me some guidance.
decide to check compression and I have 50 psi on each cylinder, is that good????
t

Your compression is even but have a hard time starting. 50 psi is low. Chances are when the motor over heated you blew a cyclinder head gasket. You will need to remove the power head from the base/exhaust housing and replace your cylinder head gasket.

Here is a parts break down of your motor.

http://www.boats.net/parts/search/BRP/JOHNSON/1968/CD-25R 1968/parts.html

http://www.boats.net/parts/search/BRP/JOHNSON/1968/CD-25R 1968/POWERHEAD GROUP/parts.html

item #11 is the head gasket

Will need a torque wrench to do the job correctly. (When you take off the cylinder head you can inspect the cylinder walls to make sure they were not damage too bad.....but these little motor can a take a lickin and keep on tickin...so wouldn't worry too much.

60 to 80 inch pounds for the cylinder head screws.

Here is the torque sequence.

http://forums.iboats.com/attachment.php?attachmentid=54249&d=1274755231



The the link with 6hp read from my 1st response has a lot of good information.

Here is a couple of links to a service manual for you motor

http://cgi.ebay.com/ebaymotors/1968...5647137QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear

http://cgi.ebay.com/ebaymotors/JOHN...70356229952QQptZMotorsQ5fManualsQ5fLiterature

You can also purchase a manual here on Iboats site as well.

Good luck my friend...don't give up on that little motor...they are great motors and hearty.

Click on this thumb it will help you remove and replace the lower unit.

 

[SteveinVA]

Re: My first motor

Awesome guys, thanks for all the replies. what a great forum. I will post up again once I get the parts and get her fired up agaiin

I also bought a new prop, the current prop was 8.25 x 5 and plastic.
I bought an 8.25 x 8.5 aluminium in the hopes of increasing the top speed. good move???

 

[jrs_diesel]

Re: My first motor

That is the same prop I have for mine (for use on my inflatable dinghy). I couldn't tell you how it performs, mainly because my engine doesn't run at the moment. It's in pieces for my big rebuild.

You're on the right track, get the cooling figured out, then run her.

 

[SteveinVA]

Re: My first motor

Okay, so got the impeller kit installed. Also cleaned out the lower unit and put in new oil and new seals. got the new 8.25 x 8.5 prop installed. Boat moves a little bit faster, the RPMS are alot lower at Wide open throtle. So we are cruising along for about 3-4 minutes if that and I can hear the rpms starting to drop off. So instead of runnig it till it quite again I jut shut it off for a while. next time started right up and ran the same as the first time. Can only run it for a few minutes before it starts to drop RPMs. So I ordered and installed a new themostat even though the original seemed to move freely. thats where I am at now, haven't had it back out since the new thermostat.
Also while test running in my bucket, there didnt seem to be much water coming out of the little spitting port. I had to put my hand in it to really tell if any at all was coming out. I let it run in the bucket atleast 10-15 minutes. flow never increased and it idled fine with an ocasional stumble at low RPM. I dont get it from all the videos I have seen on you tube there should be more water coming out
could I take off the lower unit and thermo housing and send some compressed air backward from the thermo housing to make sure the water line is clear?

 

[SteveinVA]

Re: My first motor

this isnt mine, just a comparison, mine doesn't push out nearly as much water
http://www.youtube.com/watch?v=fOFTCAmNW1Y&feature=related

 

[ONERCBOATER]

Re: My first motor

1st off there are many wiser than me here. listen to them before listening to me.

there is a possibility that bits of the old impeller are lodged in your cooling system, this would restrict water flow and still allow over heating.
Next time you take it out or run it in a 55gal drum of water do so with the cover off so that you can touch the cylinder head and engine block where the cylinders are, if the cooling system is operating as it should you should be able to touch the head and sides of the block to a count of at least 5 with bare fingers and not burn yourself.
the other possibility is fuel starvation....is your tank vented, and is the vent open to allow air to replace the fuel you have used? that is a common mistake (one i still make from time to time if i am groggy). The other possibilities are leaks in the fuel lines allowing air to replace fuel to carb....dirty carb jets, sticky float... partial check for this is to pull choke as she starts to die, if it fixes problem for a lil bit then fuel starvation is likely the issue.

yes you can use compressed air to check water lines being clear.... i personally prefer the water hose.

something else that may be of use to you over time...
http://www.sschapterpsa.com/ramblings/Johnson 9.9_15.htm
the machinist's writings are very useful, they are aimed at 9.9 to 15hp johnnyrudes but many of the findings and fixes are applicable to yours as well.

Cheers
Sean

 

[SteveinVA]

Re: My first motor

thnaks for the advice, the tank is a brand newby from walmart, didn't really look to see if it had a vent or not, Check that when I get home. Fuel line from tank to motor is brand new too. I know the water passagee are clear in the lower unit, but from the hose up I have not checked. I am gonna blow some air down threw there next time I get it out. Oh yeah, I have a laser temp guage and when I was running it in the tank, But I cant remember exactly what It was reading, next time I am gonna write them down. I do have a service manual but it was from 1969, they talk about checking the temp with some sort of wax stick that melts a certain temp?? Not much help with that one, at all really as old as it is

 

[ONERCBOATER]

Re: My first motor

the end of the pee hole is a restriction, things that pass through the water jacket and water pump...sometimes get stuck there, you may wish to poke it with the engine running, i have found a small crochet hook works wonders for getting things out, but a toothpick or a straightened fishing hook, or a wire or.... well you get the point. anyhow that may be the issue your seeing with low flow of water out of the pee hole. when you replaced the water pump did you note if the pump housing on the inside (volute case) was smooth or not, and did the new impeller fit snugly?

Sean

 

[SteveinVA]

Re: My first motor

The inside of the pump housing was pretty grimey , I cleaned it up pretty well. scraped out a lot of aluminum oxidtion out of the corners and some off the flat surfaces. got it pretty smooth and all seemed to fit well. when I pull of the lower unit I'll open it back up to see whats what. The old impeller actually had a groove wore through it by the pin, and hense stopped spinning completely. I imagine some crud had gotten in there and blocked it, dont know where the crud went.

 

[lindy46]

Re: My first motor

Have you tried hooking a garden hose up to the water tube going up to the motor to see if water is getting through?

 

[SteveinVA]

Re: My first motor

I have not, but from my understanding, there wont be much flow until the motor warms up and the thermostat opens. from looking at the thermostat housing I noticed the small bypass passage next to the thermostat, figured thats where the water is supposed to go when not warmed up so as not to put to much back pressure on the impeller. I should have checked all the passages first before installing the new impeller, hope I didn't ruin it.

 

[lindy46]

Re: My first motor

Take the thermostat out, water should flow if it's not clogged up.