Replaced rectifier, tach now reads much higher

[Vairpilot]

Hi all,

Replaced the original non-working rectifier last night on my 1986 90hp I6. I used the Radio Shack(276-1185) one as a replacement, worked great as far as charging the battery goes. However, my tach now reads about 500rpm higher at idle, and about 1500rpm higher at WOT. Previously I was showing idle around 500rpm, and WOT was around 4600. Just to be safe I kept WOT at 5000 last night, even though there was a noticeable difference in top end speed. The tach is a Faria 12-pole, so it should work with the Merc. Any insight as to which readings I should trust?

Thank you for any ideas!

 

[chrisg]

Re: Replaced rectifier, tach now reads much higher

where is this rectifier located?

 

[Vairpilot]

Re: Replaced rectifier, tach now reads much higher

It sits in the same place as the original, on the starboard side near the top, above the switchboxes.

 

[emckelvy]

Re: Replaced rectifier, tach now reads much higher

I'd say it's highly unlikely that your I-6 was actually doing 500 rpm, that's quite low. 1000 rpm sounds more like a 'normal' idle speed. Maybe a bit high but within reason. Most I-6's will get quite cranky below 700 rpm, if you can even get them to idle that low.

So your WOT was 6100 rpm?? THAT's a bit on the fast side!

What size boat and what pitch prop is on the Merc? And what speed are you getting out of it? The fact that you noted an increase in speed means you're finally getting the motor up into its power band, where before with the 'artificial' limit of 4600 rpm you weren't quite there yet.

Does the tach have any adjustments on the back and are they properly set? The old, malfunctioning rectifier might have sent a 'dirty' signal to the tach and caused the readings to be off, but since you're charging properly with the replacement rectifier, I'd expect the signal to the tach would now be 'clean'. So either there's a wiring problem or some sort of issue with the tach.

More info might help us figure this out............ed

 

[Vairpilot]

Re: Replaced rectifier, tach now reads much higher

I'm going to look into getting the idle down a bit so I'm under 1000 when I'm shifting. I don't have the diameter of the prop in front of me, but it is 19" pitch. It is a 16' Starcraft runabout, fairly light at around 1100 lbs for the hull and outboard. The redline on this outboard is 5,000, so I'm not going to push it any harder than that until I can look into getting a bit more prop on it. Wife doesn't like tearing around the lakes anyway, so keeping it a bit slow will keep her and the outboard happy until I get the RPM's under control.

The tach doesn't have any adjustments, it is preset for 12 poles.

 

[arsenalpsu]

Re: Replaced rectifier, tach now reads much higher

I have a 115hp 1984 I-6 that i need a rectifier for. Will this one work for me? It's only like 5 bucks from radioshack and $45 from www.crowleymarine.com. Is there a difference in the two?

 

[arsenalpsu]

Re: Replaced rectifier, tach now reads much higher

bump....

 

[Vairpilot]

Re: Replaced rectifier, tach now reads much higher

You hijack a thread and try bumping it? Might want to do some actual searches on here for info before you keep bumping your posts. There are a lot of helpful people on this forum, being rude and annoying is one great way to get your posts ignored.

 

[arsenalpsu]

Re: Replaced rectifier, tach now reads much higher

You hijack a thread and try bumping it? Might want to do some actual searches on here for info before you keep bumping your posts. There are a lot of helpful people on this forum, being rude and annoying is one great way to get your posts ignored.

Hijack a thread? First of all you seemed done with it as your last respons did not have a question? Second I was told that if you have a questions related to a thred you should keep it in there and not creat new a one. And it seems to me acting like you own this forum is more annoying than bumping a thread.

 

[Vairpilot]

Re: Replaced rectifier, tach now reads much higher

Did I say I owned the forum? Hardly. You have been posting incessantly, adding bump, bump, bump to every post. Then you start posting your ?'s below mine and bumping. I'm sure I'm not the only one that feels that is rude, trying to constantly push your posts to the top of the list above everyone else. Are your issues really more important than the rest of the people that post on here?

Might help you to read the sticky at the top of the forum, "How to get the best results from your question."

 

[arsenalpsu]

Re: Replaced rectifier, tach now reads much higher

Did I say I owned the forum? Hardly. You have been posting incessantly, adding bump, bump, bump to every post. Then you start posting your ?'s below mine and bumping. I'm sure I'm not the only one that feels that is rude, trying to constantly push your posts to the top of the list above everyone else. Are your issues really more important than the rest of the people that post on here?

Might help you to read the sticky at the top of the forum, "How to get the best results from your question."

To anyone I have offended by bumping I apologize. I thought it was the norm as I've seen many others do it. Vairpilot and I will finish this conversation via PMs.