1990 115 Merc 2+2 hole shot questions

[chliansh]

I have a 1990 merc 115 on a 17' Sea Ray that I just bought. Runs pretty good but has no hole shot. WOT hits about 5K rpms and it runs about 42 mph, so the 19" SS prop seems correct. I understand its the 2+2 system but do not know what to expect. Do the 4 cyl 115hp perform close to the earlier straight 6 mercs?

I tried to search for 2+2 but could not get a serch to work.

Thanks
Chad

 

[Faztbullet]

Re: 1990 115 Merc 2+2 hole shot questions

Describe your problem a little better if possible, is it lazy on take off or does it bog or hit a dead spot and then go?

 

[chliansh]

Re: 1990 115 Merc 2+2 hole shot questions

It just seems to start slow and its also slow to build rpms, like the boat is to big for the motor. It seems to run smooth as it does build rpms, no bog down or missing noticed.

 

[Dave1027]

Re: 1990 115 Merc 2+2 hole shot questions

It might need an adjustment. Like maybe the idle mixture settings on the carbs or the accelerator pump is worn out.

 

[sschefer]

Re: 1990 115 Merc 2+2 hole shot questions

A 19 is a little stiff for that combo. A vented 19 would probably help or a vented 4 blade 16p like the Stilleto Bayrunner.

There is a tiny 1/8" fuel filter behind the oil tank that can get clogged and cause these symptoms also. There are two injectors on 3 and 4 that can go bad. These are just spring rated checkvalves that act as injectors and carry the motor from two to four cylinders with the help of the accellerator pump. Getting at them requires removal of the electrical plate so it's not a simple job but not beyond learing.

Lots of things to check but start with that little filter.. Nobody but Merc seems to have them so order it ahead of time.

When you get it figured out, the hole shot should be like a shot of nitrous when 3 and 4 kick in. Mine was...

 

[chliansh]

Re: 1990 115 Merc 2+2 hole shot questions

Thanks all, I will start with the filter. Nothing close to nitrous now, more like trying to start in 3rd gear.

 

[sschefer]

Re: 1990 115 Merc 2+2 hole shot questions

Thanks all, I will start with the filter. Nothing close to nitrous now, more like trying to start in 3rd gear.

Yes, but it seems you can push through it so I'm pretty sure it's in that area.

 

[chliansh]

Re: 1990 115 Merc 2+2 hole shot questions

OK back at it today....
rpl the fuel filter (old one seemed fine) and changed out the plugs.
The syptoms are:
1. Idles smooth but dies often in neutral
2. During a WOT hole shot at about 2k rpms I notice a shake and low/slow power up to about 3k rpms then it blasts off smooth like a nitrous shot.
3. WOT with 4 people and a 3/4's of a tank of gas trimed out I get to 5200-5300 rpms so I think the prop is correct

Any suggestions?
THANKS! this site is incredible.
Chad

 

[sschefer]

Re: 1990 115 Merc 2+2 hole shot questions

O.K. Before you go buying any parts do you have a multimeter and a DVA to test the stator with? I'd like to see you test the low speed windings in the stator. The symptoms you're describing from your test today tells me that the injectors are functioning and the accellerator pump is working. That nitrous feeling should be happening around 2000 rpm so its late and that genrally means weak spark. At around 2500 RPM the high speed stator windings are comming on and that could explain when it clears up and takes off.

If you don't have the test equipment and you don't intend to work on these engines forever then you might be as well off financially if you took it in and had it tested. If its' bad you'll need to buy a flywheel puller but that's only 30-40 bucks so it's a worth while expense.

 

[chliansh]

Re: 1990 115 Merc 2+2 hole shot questions

Multimeter I have, whats a DVA? Please advise me on what I need and how to proceed? The vibration is all the way up to 3k rpms, if I would throttle back it would continue indefinately.


I did do quite a bit of reading and it sounds like nothing quite performs like the early 80's inline 6 "tower of power". I skied behind one years ago and was blown away by the way it could rip us out of the lake on deep water slalom starts, oh and the scream it made while doing so. I sure was disappointed the first time I dropped the hammer on the new to me 115, expectations were far to high.

 

[MercGuy]

Re: 1990 115 Merc 2+2 hole shot questions

Hi Chad,

I'll chime in with another possibility.

I have a 1998 115 2+2 and I suffered with symptoms similar to what you describe for years. I especially note that you mention that you can idle for a while and then it dies, which mine did a lot. When that happened I would need to pump the primer bulb to load the carbs with gas and I was ready to go again.

The problem in my case was leaky exhaust cover plate gaskets. Eventually I noticed water leaking from around the bolts that hold the cover on (there are quite a few of them, the cover is on the Port side of the engine).

When I took the cover plates off there were carbon tracks across various chambers that were supposed to be sealed by the gasket. I cleaned it all up and put it back together with a new set of gaskets (that were much higher quality that what I took out).

Now my engine runs better than it did when I purchased it new. My theory is that the leaky gaskets reduced the pressure/vacuum that is supposed to be present in a 2 stroke crank case. This reduction of pressure and vacuum cycles reduced the efficiency of the fuel pump causing my problems with extended idling, and probably caused the engine to run lean resulting in stumbling during the 2 to 4 cylinder transition. (Actually I had stumbling anytime I tried to accelerate, but it was the worst at the 2 to 4 transition).

All theory on my part, but it did the trick for me and I am happier with my 115 now than I've ever been. 860 hours and counting !!!

-Steve

 

[sschefer]

Re: 1990 115 Merc 2+2 hole shot questions

MercGuy, that's a definite possibility and a very common problem with these engines. I've had it myself but I've learned to be systematic about these things or you can easily pump money into them with zero gain.

Chad do a search on DVA's on this site, there are several threads about them. CDI sells them I believe but there are instruction here on how to easily make your own for a lot less money.

 

[MercGuy]

Re: 1990 115 Merc 2+2 hole shot questions

sschefer,

Very interesting that you say it's a common problem, as I've never heard of it before and assumed that mine was a rare case.

To the OP, an easy way to check this would be to simply re-torque the bolts. I did that and it seemed to completely fix the problem. I only replaced the gasket to make sure everything was right.

The factory manual gives a torque and tightening sequence that should be followed exactly.

-Steve

 

[chliansh]

Re: 1990 115 Merc 2+2 hole shot questions

Steve,
Thanks for the tip! I have a manual on order any chance you could send me a pic of that page? Or even if you could give me the torque sequence and #'s? I am anxious to try it and do not want to screw anything up.

Thanks
Chad

 

[chliansh]

Re: 1990 115 Merc 2+2 hole shot questions

OK tried all things mentioned above and still have the "fall on its face" take offs. Only thing new noted was after I ran it at about 1/4 throttle for 15-20 minutes I stopped and tried a hole shot and it was even worse than normal? It ran extra rough with lots of vibrations. Aftrer awhile I tried it again and got the std slow start. Boat runs great at full throttle 43 mph+ with a full load?

Is it getting too much gas?

 

[achris]

Re: 1990 115 Merc 2+2 hole shot questions

Download a Merc service manual HERE. Password for the file is <ribforum>.
Look HERE for instructions on building your own DVA (Direct Voltage Adapter) for a multimeter (Essentially it's a peak voltage meter, and the only way to check the ignition system components. Instruction on it's use are in the manual).

With this problem I would go back to basics. Check compression, check for healthy sparks on all 4 cylinders, new plugs, new fuel pump diaphragms.... and check the carb and timing synchronisation.

Chris.............

 

[filo_bedo]

Re: 1990 115 Merc 2+2 hole shot questions

Hi Guys

This sounds like a similar problem that I am having. My 115 2+2 starts fine but idles rough. Then when you give it throttle it starts to run on all 4 cyl but then will drop 1 or 2 and will continue to run while down on cylinders, then 3 and 4 will kick in again and power will be up, then lose the 2 again and so on. it never can hold all cylinders running for any period of time!
All the plugs have been changed and this has not helped a thing.
Any auggestions on where to start to find this gremlin? I dont know if the +2 cylinders kick in electronically or because of vaccum pressure? Could it be a fuel pump? Could it be this little fuel filter mentioned earlier in the thread?
Any help would be greatly appreciated!

 

[199675hpforce]

Re: 1990 115 Merc 2+2 hole shot questions

I had 2000 115hp wow that sucker hit harddddd, launch city.

 

[borderboat]

Re: 1990 115 Merc 2+2 hole shot questions

I have a 1993 115 (2+2) I suggest you download the manual that achris posted a link to. Go to the timing/sync section and set the timing & sync the carbs. With the 2+2 system it is imperative to have carbs kicking in & out at the right time or you'll have nothing but grief. It really helped my holeshot.

 

[Dave1027]

Re: 1990 115 Merc 2+2 hole shot questions

I have a 1993 115 (2+2) I suggest you download the manual that achris posted a link to. Go to the timing/sync section and set the timing & sync the carbs. With the 2+2 system it is imperative to have carbs kicking in & out at the right time or you'll have nothing but grief. It really helped my holeshot.

What do you mean by "carbs kicking in & out at the right time"? As far as I know all that needs to be checked on the carb throttles is that they are all completely closed at the idle position.