trim angle?

[94OMC]

Hi, I have a used boat that has a 1994 OMC Cobra SX drive. I think the trim gauge is off, and I believe the sending unit can be adjusted on the drive.

Here is what it currently looks like fully trimmed down (Pict3072s.jpg)

And here is what it looks like when the trim gauge says it is trimmed (not tilted) all the way up (Pict3073s.jpg)

The level is an extension of the keel surface for reference.

When the drive is trimmed up, should the anti-ventilation plate be on a parallel angle to the bottom of the keel, or should it be on an angle where the prop is higher than the front of the drive?

thanks

 

[Limited-Time]

Re: trim angle?

I do not believe the trim angle is tied in any way to the boats bottom. Not sure about Cobra SX Drives............but the Merc drives (alpha 1 gen II)are governed by the factories maximum allowable extension distance of the rams while under power. I'm sure it ties back to the operational angle of the u-joints, some how.

 

[Gary H NC]

Re: trim angle?

Most trim gauges are not very accurate.With it trimmed fully down the trim sender could be adjusted to show full down on the gauge.Usually just loosen the 2 screws on the sender and turning it very little until the gauge reads correct. Looking at the pics your gauge is way off.

 

[94OMC]

Re: trim angle?

Most trim gauges are not very accurate.With it trimmed fully down the trim sender could be adjusted to show full down on the gauge.Usually just loosen the 2 screws on the sender and turning it very little until the gauge reads correct. Looking at the pics your gauge is way off.

I just came back in from tinkering with it. Now the gauge doesn't read at all, I think my sending unit has sent it's last signal.

 

[Gary H NC]

Re: trim angle?

You may want to check the plug where the wires come into the engine compartment. If i recall correctly it is a flat style plug with a brown and black wire.You should see it behind the engine after it comes through the transom.
They are known to corrode.

 

[donnymac]

Re: trim angle?

Me thinks what it looks like on the trailer and what it feels like in the water are 2 different things. I have left my leg "trimmed out" for my sweet spot at 32mph. Forgot at the boat launch to lift it all the way. Thankfully it cleared the launch. But by just looking at it on the trailer it was hard to tell it was trimmed out. But in the water...

 

[a70eliminator]

Re: trim angle?

I had the sending unit go bad on my Cobra, gauge would jump around and sometimes not work at all. Good luck finding a replacement if someone has one they ususlly want a couple hundred bucks for it. I actually fixed mine. I dug out the bad rheostat, it's sorta caulked into the main body, I bought a new rheostat through an online electronics store and epoxied it into the main body, cost me all of $6.00 and and many hours of my play time, but it works great now, the resistance values are given in the Cobra repair manual too + there is a number on the rheostat and it is a common piece, the trick is digging it out and leaving the main body undamaged.

 

[94OMC]

Re: trim angle?

a70 - thanks for the tips. It sounds like mine is doing the same thing yours was. Last night it wasn't working, but now it is. It's still reads high when the drive is fully down, but oh well. I may have to dig into my sensor like you did.

You don't happen to have those resistance values, do you?

 

[MikDee]

Re: trim angle?

I never had a working trim gauge on any of my boats! I just trimmed by feel, & ride. I think the trim sender on the Mercruiser is under the bellhousing, and that needs to come off to repair the sender, so I never bothered. If you listen you can hear the trim pump, and get used to the sound of it when it bottoms out (all the way down), (or all the way up). I just keep it dowm when starting till I'm on plane, then continue to raise it up till my prop starts to lose grip by the sound, feel, & tach, then just lower it abit to the sweet spot. Off plane, you just need to put your trim all the way back down.

 

[a70eliminator]

Re: trim angle?

a70 - thanks for the tips. It sounds like mine is doing the same thing yours was. Last night it wasn't working, but now it is. It's still reads high when the drive is fully down, but oh well. I may have to dig into my sensor like you did.

You don't happen to have those resistance values, do you?

Yes I know the values and you can certainly check them with an ohm meter through the wire harness plug, you should see anywhere from 0-200 ohms plus or minus 10 depending on the position of the feedback arm. Once you get used to having one it's hard to go without for me anyhow, like my motorcycle that has LED telling what gear your in, you don't really need it but it's definately nice to have.