Cap and rotor replacement/tune up - Merc 5.7l 2bbl Alpha

[burtonrider11]

Hi all, my apologies if this has been covered before. I am in the process of replacing a starter on my boat. While I have everything torn apart, I figure this would be the best time to do a fairly complete tune up: new plugs, wires, oil/filter, cap and rotor.

I am child of the fuel injection era, so carbed motors with distributors are somewhat foreign to me. Is there anything I need to know prior to changing the cap and rotor. My plan is to mark where the current cap sits in relation to a specific cylinder and line up the new one with that mark/cylinder.

I read in the merc manual that to replace the rotor, I need to use some Loctite 271 on the distributor shaft and rotor. A guy I work with says not to do that, that I'll never get it off. I tend to lean toward what the Merc manual says, but I'd love some input.

I replaced the fuel filter earlier in the season, we have less than 20 hours on the new one, would I be okay to leave that? I always use Startron when I fill up and will top off my tank when winterizing with the Rec90 (pure gas).

Any thoughts/advice would be welcome!

 

[harleyman1975]

As long as you don't loosen the distributor bas no need to mark anything just romve cap and transfer wires one at a time from old cap to new. rotor just pulls straight up and off and new one pushes down in its place and only goes on one way.

 

[burtonrider11]

As long as you don't loosen the distributor bas no need to mark anything just romve cap and transfer wires one at a time from old cap to new. rotor just pulls straight up and off and new one pushes down in its place and only goes on one way.

Thanks Harley! Do you think I need the Loctite as specified by Merc or is that overkill? I'll be sure not to loosen the distributor.

 

[GA_Boater]

You should reread the section about using red Loctite 271 to hold the rotor on. That's the wrong stuff and the wrong application. The rotor will stay on with nothing added.

Right from Loctite with my added underlines; [h=2]Loctite? Threadlocker Red 271?[/h] [h=3]Nut and Bolt Locker[/h]

Loctite Threadlocker Red 271 is designed for the permanent locking and sealing of threaded fasteners. The product cures when confined in the absence of air between close fitting metal surfaces. It protects threads from rust and corrosion and prevents loosening from shock and vibration. It is only removable once cured by heating up parts to 500?F (260?C).

 

[burtonrider11]

You should reread the section about using red Loctite 271 to hold the rotor on. That's the wrong stuff and the wrong application. The rotor will stay on with nothing added.

Right from Loctite with my added underlines; [h=2]Loctite? Threadlocker Red 271™[/h] [h=3]Nut and Bolt Locker[/h]

Loctite Threadlocker Red 271 is designed for the permanent locking and sealing of threaded fasteners. The product cures when confined in the absence of air between close fitting metal surfaces. It protects threads from rust and corrosion and prevents loosening from shock and vibration. It is only removable once cured by heating up parts to 500?F (260?C).

Okay thanks, I am leaning toward not using it. I have attached a screen shot taken from the Merc Service Manual - this is why I was asking.

 

[GA_Boater]

I stand corrected and sorry for doubting your reading ability. :facepalm: First time I've seen the rotor and sensor wheel replaced as a unit.

Still, step 11 says to let the Loctite cure while the distributor is inverted. This means the distributor needs to be removed, which in my mind isn't part of a normal tune-up.

I think I would examine the rotor before deciding to replace it. Possibly you only need to do the distributor cap.

 

[flipbro]

I use the blue locktite. Never an issue..

 

[burtonrider11]

I stand corrected and sorry for doubting your reading ability. :facepalm: First time I've seen the rotor and sensor wheel replaced as a unit.

Still, step 11 says to let the Loctite cure while the distributor is inverted. This means the distributor needs to be removed, which in my mind isn't part of a normal tune-up.

I think I would examine the rotor before deciding to replace it. Possibly you only need to do the distributor cap.

No need to apologize, I just wanted to get some clarification on it. I am leaning toward not using anything at all, but my fear is that when the engine revs up, centrifugal force may spin it right off. I do not want to remove the whole distibutor if at all possible. Maybe I just use one drop of it to at least give some bonding properties? I may not need a rotor, but I've already purchased the cap and rotor. I don't have a detailed service history and it appears as if it's been some time between tune ups. If I don't replace the rotor, how do I best determine if the existing is up to snuff? I'll take pictures to see if that helps.

I do have a co-worker who, while not a mechanic, says NOT to use any bonding agent. He said he has replaced rotors/sensor wheels before and never used Loctite, never had a problem. I really need some guidance on this one!

 

[burtonrider11]

I pulled the cap and the rotor/sensor wheel. Pics attached. The parts look better in the pics than in real life The first thing I noticed when pulling the cap was that it only had 3 out of 4 screws and the 3 remaining weren't tight at all. Which lead to no surprise when I pulled the cap and the old seal disintegrated as I was pulling it. It is doubtful this thing has ever been changed or if it had been, whoever did it, was sloppy. There isn't a ton of corrosion, but it definitely looks like it's time to replace both cap and rotor. Is there anything else I should service while I have the cap off?

I noticed some rust/corrosion in the distributor cap area , not sure how to best fix this....

 

[NHGuy]

I use the locktite. Just be prepared to lever the old rotor off when removing. Reason I do it is cause boats bounce around and you don't want the rotor hopping off the shaft.
I got a new to me boat this year and had a miss when it hit big bumps. I found the rotor not stuck down and sliding pretty easily on the dist shaft. So I locktighted it.
Don't worry about the permanent-ness. You aren't putting it into metal threads. And in a pinch the rotor can be broken off, and the old locktite heated. I haven't needed to, but it is possible to heat it enough to remove.