90HP V4 stumbles when tilting engine down

[peterskeeter]

My 1989 90HP Evinrude seems to be having an idle issue. Wondering if anyone has experienced something similar to this as I am thinking the carb floats may be the cause.

Engine idles fine whether it is in the water or out the water on flush muffs. When you tilt the motor down, the engine wants to kill, as if it is flooding. It is doing this in and out of the water. However, it does run fine when you are under way with the motor in the tilted down position with a load. Is this somewhat normal for these engines? Anyone have an idea or experienced this before? Not a big problem, just a little irritating

 

[ezeke]

Re: 90HP V4 stumbles when tilting engine down

The motors are not designed to run tilted up, just through the trim range.

 

[peterskeeter]

Re: 90HP V4 stumbles when tilting engine down

It is stumbling within the tilt range. It actually starts to stumble just when the motor goes past being level, when tilting the engine downward. It just doesn't seem normal. I have removed the hood while the engine is running to see if any linkages are moving for some reason when the angle of the engine changes. I have also looked for leaks coming from the carbs and haven't seen anything abnormal. Engine runs great otherwise

 

[ezeke]

Re: 90HP V4 stumbles when tilting engine down

You may not have your floats set correctly. It is not hard to fix, but you have to take the carburetors off to do it.

You are not priming (with the primer bulb) the carburetors with the engine tilted up are you?

 

[peterskeeter]

Re: 90HP V4 stumbles when tilting engine down

I have set floats before on other motors and motorcycles. It's not too hard but is the procedure the same for this motor? Do you flip the carb over and make sure the top of the float lands parellel to the body of the carb where the bowl mates to it?

I am not priming the the bulb when it is tilted, just simply letting it idle. It is wierd, I mean, it starts to stumble exactly when the motor goes downward just past being level. Once the motor is level, all is fine. All is fine still even when you tilt up past it being level, it just seems odd to me. Matter of fact, it runs fine when even when tilting extremely up on an angle....

 

[ezeke]

Re: 90HP V4 stumbles when tilting engine down

It is the same; float is parallel to the carburetor base when flipped upside down.

 

[peterskeeter]

Re: 90HP V4 stumbles when tilting engine down

Thanks Ezeke, I will try to adjust the floats and see what happens. Thanks again for the advice!

Pete

 

[Mas]

Re: 90HP V4 stumbles when tilting engine down

I mean, it starts to stumble exactly when the motor goes downward just past being level.

This will open up the float and you're flooding your carb...if I'm reading your response correctly. Trimmed all the way in so the shaft is closest to the lower transom? This will change the float angle and open it up, thus running rough.

MAS

 

[peterskeeter]

Re: 90HP V4 stumbles when tilting engine down

MAS, it is happening when trimming just past being level, before being trimmed fully down...
Are you saying what I have is somewhat normal or should I go ahead and pull the carbs and adjust the floats still? The motor runs fine other than this small problem....

 

[Mas]

Re: 90HP V4 stumbles when tilting engine down

Still sounds like a float issue. If the position that the motor is tilted is not the position you run, I wouldn't worry about it. But I am still a bit confused about the position you're describing. You want the prop shaft parallel the water's surface in flat water, and maybe slightly trimmed out to raise the bow in rough water.

The motor should not be trimmed in so far that the shaft is no longer parallel and is trying to force the bow down into the water...not very efficient.

MAS

 

[peterskeeter]

Re: 90HP V4 stumbles when tilting engine down

When I am about to jump out of the hole with a full load, I have to trim just below being level. At this point, the RPM's will start to drop and the motor may kill if you do not increase the throttle. Exactly as soon as the motor passes being level (prop shaft also), RPM's will drop, either in the water or out the water.
At first, I thought it was something exhaust related when I first bought the boat as trimming down would place the upper exhaust reliefs in the water, then I noticed it would also do it out of the water on the muffs. If the problem does not go away, I will pull the carbs and check the floats.

Sidenote, I have just finished seacasting the transom and have since raised the motor off the transom significantly. It still exhibits this problem on the muffs but I haven't tried it yet in the water.

 

[peterskeeter]

Re: 90HP V4 stumbles when tilting engine down

You want the prop shaft parallel the water's surface in flat water, and maybe slightly trimmed out to raise the bow in rough water.MAS

Besides the point, but shouldn't you trim the motor down in rough water so that the bow breaks the waves? In smooth water, you trim the motor out (up) so that the majority of the boat rides out of the water for greater speed and efficiency, right?

 

[ezeke]

Re: 90HP V4 stumbles when tilting engine down

.....trim the motor down in rough water so that the bow breaks the waves? In smooth water, you trim the motor out (up) so that the majority of the boat rides out of the water for greater speed and efficiency.......

That's the way I do it. Also, it's good to have the A/V plate parallel to the water as much as possible.

 

[Mas]

Re: 90HP V4 stumbles when tilting engine down

Besides the point, but shouldn't you trim the motor down in rough water so that the bow breaks the waves? In smooth water, you trim the motor out (up) so that the majority of the boat rides out of the water for greater speed and efficiency, right?

Yes, you are right ...my error.

MAS

 

[emdsapmgr]

Re: 90HP V4 stumbles when tilting engine down

When running the engine in tilted positions, it is not unusual for a small amount of fuel/oil to drip out of the throats of the carbs. The excess fuel/oil will accumulate in the bottom of the airbox. When you first tilt it in, the excess fuel gets sucked into the airbox drain hose and into the crankcase on #4. This excess can sometimes cause it to run rough, smoke for a minute or so-till the fuel is consumed. Then engine will run normally. That drain hose is put there just for that reason. This is not an unusual situation and setting the carb floats to the proper levels may reduce this problem somewhat.