Wrong Timing???

[97_Manta_Ray_CR]

Thank everyone who looks and advises me with this

I have a 18' 1997 Manta Ray Bow Rider with a 96 Mercruiser 3.0 and an Alpha One Drive...

At the beginning of this season I rebuilt the carb and after that the motor started dieseling and I talked to a few boating people and they suggested that the timing was off so, this past Thursday I adjusted the timing and got the motor running good on the hose and it dropped the RPM's and I got them down to about 700. Now move forward to Saturday we took the boat out and i put it in the water and I wouldn't stay running cause the RPM's were to Low. Also My full throttle is only 3500 RPM's and I cant get anymore out of the engine.

Prier to adjusting the timing I was getting max RPM of 4800 and I have a 19 degree prop.

I followed the directions in the shop manual and put the timing at 1 btdc and when look at the timing after removing the jumpers I cant tell where the timing is but every so often it shows at 1 btdc.

Any advise would be great

Thanks Chris

 

[Fishermark]

Did you notice a change in the engine when you connected and disconnected the base timing jumper? And when yo added the jumper, you supplied the 12v as well?

 

[97_Manta_Ray_CR]

I did not notice a difference when I put the Jumper in and I thought that was a little weird, what do you mean supple 12v to what?

 

[bparsel]

I think he's referring to the base timing plug. It plugs into the distributor and then you connect the 2nd wire to a 12v source. If setting the timing in "Base" mode it should run a little rough and then run well when you remove the base timing plug. If timing in "Base Timing" mode I believe your timing on the 3.0 should be at 8 degrees BTDC.

 

[97_Manta_Ray_CR]

Thank you I will look into that, I have found that I didn't connect the two wires together from the shift interrupter so that could be my issue of the motor not being in base timing. Know my next question is since Ive ran the engine for a mine at 3500 RPM's did I cause any damage to the engine?

 

[97_Manta_Ray_CR]

These are the wires I am talking about that I didn't connect to get the motor into base timing, I just unplugged the white and black strip wire and put the jumper on the distributor

 

[bparsel]

This is on a stock EST ignition correct? If you go to youtube, Michigan Motorz has a good tutorial on timing your exact engine. They do use a plug rather than jumper wires etc. But yes, sounds like you never had the boat in Base mode. You would have know if you had.

Running it up to 3500 to check timing should have no ill effects......running it WOT around the lake would be a bad thing.
Sorry, I'[m very familiar with the EST ignition...but not the 3.0 Alpha combo.

 

[97_Manta_Ray_CR]

I did run it for a little while at WOT on the lake I would say about 4 to 5 miles total with 4 adults on board... How can I tell if I did something to the engine?

 

[bparsel]

If it didnt go BANG and you have no strange noises it should be fine....and 3500 rpm's shouldnt be WOT. Propped right it should be in the 4400-4800 range.

 

[97_Manta_Ray_CR]

Yes I do know that that is the correct WOT, what I mean is that with my throttle all the way full I was only getting 3500 RPM's

 

[Maclin]

I am curious as to how just a Carb R&R would have affected the timing. With an EST it is set and forget unless it is removed or moved.

After adjusting the timing and now cannot get any RPM's it is probably not at the proper initial advance, either too little or a LOT too much. Too little and it is down on power due to cylinders firing late. With too much it will still be down on power but because they are firing way too soon and that is way harder on the engine, can ruin it in short order.

 

[97_Manta_Ray_CR]

After the Carb R&R the motor would diesel and it was recommend to check the timing, I thought I had the motor in base timing but actually I didn't. Now that i know the correct way to set the timing I will try again and see whats going on. If I do get the timing set back correct and she starts to diesel again I don't know where to go from there

 

[Fun Times]

Just to try and clear up any possible confusion!!
Besides the dieseling after the carb rebuild, did the engine run good enough so that you were able to obtain full RPM range of around 4800 RPM?.... How many people where in the boat after carb rebuild?.
Then it seems you came home and adjusted timing and now it won't go past 3500 RPM with a boat load of people...Thanks.

 

[97_Manta_Ray_CR]

yes your post says everything correctly... I adjusted the timing because the person I bought the boat from said with the carb R&R the timing might be a little off... He was to busy to come over and look at it with me so I told what it was doing and he suggested that I adjust the timing. And now here we are, took the boat out saturday with 4 adults on it and I only achieved 3500 RPM. Before I adusted the timing I was getting 4800 RPM's after the carb R&R

 

[Fishermark]

You should be fine once you correctly set your timing. After actually getting it into base mode using the jumper with the 12v - then set it to 1 degree BTDC. Then remove the jumper and reinstall the shift interrupt connector and you will be fine.

 

[97_Manta_Ray_CR]

Thank everyone for there advice and words of encouragement I will work on getting the timing back to where it needs to be, and I will post an update within a day or two.

Thank you again

 

[achris]

Before you pulled the carb, the engine was running fine. You pulled the carb (without touching anything else), stripped and cleaned it. Reassembled and reinstalled it on the engine, then the engine was dieseling, so the timing shifted all by itself.....

My suggestions. Return the timing to where it was. You need to do the timing precedure properly, without any deviations from the genuine Merc service manual, and set it to 1? ATDC. With the engine running, jumper the white wires on the distributor, disconnect the shift interrupt switch and join the ENGINE HARNESS side wires together and set the timing to 1? ATDC. No need to supply 12v anywhere, just as the book says. Once you do that, then start working on getting the carb back to working. Why did you pull it apart in the first place?

Chris.......

 

[97_Manta_Ray_CR]

I pulled the carb and did a R&R because I couldn't get the motor under 1300 RPM's before it would stall out and asked many people on here and in person and they suggested a carb R&R, so I did it and the RPM's came down to 800 like the manual stats is a good range.

Your saying set the timing to 1 ATDC but the shop manual and everyone here says 1 BTDC so which is it?

Thanks
Chris

 

[achris]

I suggest 1 ATDC because Merc released a bulletin in 1998 regarding these engines blowing head gaskets, and recommend changing the timing from 1 BTDC to 1 ATDC....

Chris.......

 

[97_Manta_Ray_CR]

OK I just found that bulletin but my engine is a 1996 so should I still do 1 Atdc or keep wit 1 btdc?