can stator problems cause knock?

[superjuice]

Greetings, I am the proud new owner of a 1972 19' aquasport CC with a 1985 75hp 4cyl mercury outboard located in CT. I bought the boat knowing that the engine was in need of repair due to a loud knock that the previous owner experienced. According to him he limped in and pulled the boat last summer. He also didn't have it winterized because he figured it was a goner, which it may well be.

I just opened the motor up and a bunch of wires going to the stator are split and corroded. Mostly the yellow wires, they just crumbled away in my hand. I plan on doing a compression test tomorrow, hoping for the best.

Obviously the wires or stator need to be replaced but could a stator failure cause a knock, or would it just die. Just wondering if I should sink any money into this engine or just find a new one. The good thing is that it has a 5 year old lower unit, replaced at the local dealer. I was thinking of even finding a 84-88 90hp in better shape and swap that in using the same controls and maybe even the lower unit. Thanks for any help you guys can offer, John.

 

[CharlieB]

Re: can stator problems cause knock?

The yellow stator wires are the battery charging circuit and will not contribute to any 'knock', that is a definate problem with a rod or piston.

 

[superjuice]

Re: can stator problems cause knock?

I ran a few new wires and the engine runs, compression on 1-130, 2-125, 3-130, 4-120. The upper carb is dumping gas while the lower isn't showing any. are these primary and secondary carbs or is the top one for cylinder 1+2 and the lower carb is for cylinders 3+4?

Also, i pulled the plug wired on 3 and then 4 while it was running, no change so no spark i would assume. I had checked the top 3 with a spark tester and i thought they were good, but #4 is too far down to put it on. What would keep #3+4 without gas and spark, or would it have to be 2 separate problems? Nice to hear it run, I don't hear any knock but it's pretty loud from 1200 rpm's up.

update: i swapped the #2 coil pack with #3 and still no spark on #3 but there is on #2. This points me towards the switch box.

 

[superjuice]

Re: can stator problems cause knock?

If i remove the nut on top of the flywheel, can i get at the stator from there? The yellow charging wires are broken just out of reach.

 

[superjuice]

Re: can stator problems cause knock?

Unfortunately i just found out that rpm's above 1800 on muffs can be detrimental for the engine. I ran it multiple times today beyond 4000 while trying to diagnose and keep it going. Im usually really good with engines but this is a new breed to me, I hope its not in any worse shape than it was this morning. Looks like another compression test is in order, I did however find a used switch box locally for $100, picking it up on monday. I guess i'll pull the carbs tomorrow to see why the lower one is dry.

 

[CharlieB]

Re: can stator problems cause knock?

If this 'knock' cannot be heard it idle speeds there is a possibility that it is spark knock, caused by incorrect ignition timing. Easy to occur if someone has been messing with the motor.

Read the 'sticky' posts at the top of this forum, find the links to the service manual and download the manual for your motor.

Clean the carbs and install new gaskets using carb rebuild kits. Then adjust the carb linkage and timing following the directions in the service manual. Timing is critical, reduce the factory full advance setting by 2 degrees to allow for the poor quality fuel today.

Run the motor again and see if the noise is gone.

Repost your progress.

 

[superjuice]

Re: can stator problems cause knock?

I replaced the stator with a new PDI unit. Replaced the switchbox with a used unit (90 day warrantee). Bought all new fuel line, fuel/water separator, and bulb as well, looking forward to starting it up tomorrow. Still need to rebuild the carbs with the gasket kits i purchased but one thing at a time. I just want the #3&4 cylinders to fire first. Thanks again for the help!

 

[superjuice]

Re: can stator problems cause knock?

Decided to run it off of a new 6 gal. tank to make sure the fuel isn't bad. Replaced the water pump and lower unit oil, looked kinda milky but i'm gonna let that slide for now. Cleaned out the carbs but did not replace the float, needle, or seat. It looks like someone had been in there before because it all looks good, new float, springs and whatnot. Unfortunately it still doesn't want to idle. It starts to idle then revs up and down until it finally stalls. Bought a used set of coils and wires on ebay so ill swap them in later this week. In the mean time i replaced just about every wire in the t-top and console to keep things moving along. I hope to be on the water soon!

 

[superjuice]

Re: can stator problems cause knock?

The motor is running well, I replaced the coils and wires "used set off ebay." The wires were suspect b/c i saw arcing from just outside coil #3. There is a distinct valve noise but it does not sound like a "knock" to me. Hoping to launch it this weekend if all goes well. Thanks guys, John.

 

[Mi duckdown]

Re: can stator problems cause knock?

REED Valves. can't Hear them

 

[superjuice]

Re: can stator problems cause knock?

Took the boat out saturday for about 3 hours. Could only get up to 18 mph but it was surging from 4000 rpms to 5000 rpsm and was jumping forward(not cavitating) Burned about 20 gallons in those 3 hours. Took it for a quick spin on monday and felt the same surging but it finally caught and i hit 26 mph before coming to a bridge/no wake zone, also where I pull the boat. Hopefully i blew out whatever was bogging my engine down and it will run better from the start next time. Not sure i hear any knocking, and I know now its not the valves(new to 2 strokes) but it sure sounds like a higher pitched ticking to me. Getting closer anyway, Thanks again.

 

[CharlieB]

Re: can stator problems cause knock?

The surest way to destroy a motor is to keep running it with a noise or with anything not perfect with the carbs or ignition.

Follow the link, see if your service manual is still available. READ it and follow the directions to adjust the carbs, and ignition EXACTLY as spelled out. If the motor does not perform correctly, find out WHY cause you will destroy it otherwise.

http://forums.iboats.com/showthread.php?t=309079

 

[superjuice]

Re: can stator problems cause knock?

I called my local merc dealer and they cannot find my exact service manual. Can someone please tell me how to replace the trigger. I have a new CDI unit in hand. I have the stator off and the flywheel as well. I can't seem to get the trigger off though. i have broken 2 three jaw gear pullers and think I'm going about this the wrong way. any help would be appreciated, thanks.

 

[Maxz695]

Re: can stator problems cause knock?

after taking the flywheel off the hub the trigger should stretch enough to just barely get it over the hub Be careful not to lose the spring or the plastic guide If so you gonna have to make one out of thick wire or something. As for the knocking i was getting the same thing knocking at WOT after the engine ran a bit and then at idle when returning. I had purchased a blown power head with bad pistons and didn,t have a Micrometer so I just went ahead and changed over the reed cage and new bearings I had just recently bought including the upper main lower main and both sets of needle pin bearings for the connecting rods. I went for a test ride today and ran the sucker long and hard and Not so much as a clunk knock or tick other than the usual sound of the lower ball bearing common tho my 40 HP 2 stroker. I would suggest getting the specs for the crank and a micrometer and see if your that far out that it needs to be replaced. Cavitation and lack of knowledge at the time was the downfall of my crank. Continuing on the course your taking can only make things worse Much worse

 

[Gibbles]

Re: can stator problems cause knock?

Seloc Manual:
http://cgi.ebay.com/SELOC-SERVICE-M...8?pt=US_Texbook_Education&hash=item56458f4858