150hp optimax installed to high or not? pics attached

[acuaholic]

Hi, I have a tahoe 195 deck boat that I recently purchased, it has a 150hp merc optimax installed, first thing I noticed on first run is that I dont have much trim play because the prop starts slipping and in tight turns same thing I figured I probably need to lower the engine a slot or two, but when I looked on the plate I could easily tell that the engine used to sit on the very top hole or all the way down, that bugs me because either someone raised it for better performance, or someone like me thought that it needs to be lowered tried it and figured out that it wasnt a good idea and raised it back, thats the only thing that made sense with the marks on the top holes. I didnt think much of it thought I would try and drop it and see, but local dealer wants $300 to drop or raise, so if I am wrong this might cost me 600$ or more, I want to only move it once if needed. I am attaching picture, I do have a notch in the back of my boat so I am not sure where it is supposed to sit, the av plate is now about 2.5" above the very bottom part of keeln. could this also be the reason why the water pressure is a bit low at wot?
Is there a way to find out original dealer install location? Thank you very much.

Thank you very much.

 

[acuaholic]

Re: 150hp optimax installed to high or not? pics attached

Forgot to mention that I am looking to buy a 4 blade ss prop, and I was told that it helps when outboards are installed higher.

 

[JB]

Re: 150hp optimax installed to high or not? pics attached

Looks marginal to me. Does the prop ventilate when at WOT? Ask your prop question in the Prop Forum. I doubt it.

 

[Faztbullet]

Re: 150hp optimax installed to high or not? pics attached

That too high for a deck boat but about right for a bass boat... drop it all the way down if you ski/tube.

 

[acuaholic]

Re: 150hp optimax installed to high or not? pics attached

Yes the boat will be used mostly for tubing wakeboarding and some fishing.

 

[acuaholic]

Re: 150hp optimax installed to high or not? pics attached

and no I didnt notice prop ventilation at WOT ( I am guessing you mean slip) but I have only had it out on really calm water, I just tried taking a pretty wide turn at wot and prop slipped, I had to stop and re plane again. the boat did come with a small hydrofoil that I will be taking off before I take her out again. what should I specifically check on the water before dropping the engine and after to know that its the right height?
Thanks

 

[glenn property of pam]

Re: 150hp optimax installed to high or not? pics attached

at full speed cavation plate should be just above the water (2 person job to check that). way above the water then it will break surface and ventilate (drag air in). to low and the foot/leg will act as resistance. Thats what they told me but then they add the all important.......it depends on how you plan to use the boat. With out a jack plate it does look a little high

 

[JB]

Re: 150hp optimax installed to high or not? pics attached

The part commonly called a cavitation plate is more correctly called an anti-ventilation plate. It is to prevent what glenn explains as ventilation. It is a common problem with outboards mounted too high or trimmed too far out. The AV plate should be riding right on the surface on plane so that the prop cannot get air.

 

[Fun Times]

Re: 150hp optimax installed to high or not? pics attached

See if this helps give you some ideas,

http://1manual.com/Mercury manuals/Service Manual PDFs/OptiMax/855347r1/1d.pdf

 

[acuaholic]

Re: 150hp optimax installed to high or not? pics attached

I will try to get the boat out on the lake tomorrow and check the av plate on plane, and I did read through the manual thanks, my biggest thing is that with that notch in the back of my boat, do I measure to or check the av plate vs keel at the very end where its higher up or where the keel is at the lowest point? and why would someone raise the engine in the first place? what would that benefit them from the original lower installed points?

 

[kls2020]

Re: 150hp optimax installed to high or not? pics attached

call the boat manufacturer and ask their tech dept for a recommended engine height on your model

 

[glenn property of pam]

Re: 150hp optimax installed to high or not? pics attached

I will try to get the boat out on the lake tomorrow and check the av plate on plane, and I did read through the manual thanks, my biggest thing is that with that notch in the back of my boat, do I measure to or check the av plate vs keel at the very end where its higher up or where the keel is at the lowest point? and why would someone raise the engine in the first place? what would that benefit them from the original lower installed points?

most things have a plus and a minus. in shallow water a higher motor setting is a plus that you have to pay for with a loss of performance. A jack plate allows you to do this with less of a negative impact and a adjustable jack plate allows you to do it with no loss. You will have to set your boat up for what you intend to use it for and except some minus affect.
One other note that has not been mentioned is on some boats you are limited by the splash well and motor conflicting when tilted. My motor has to be set one notch higher than i like as the engine when tilted hits the splash well

 

[misery]

Re: 150hp optimax installed to high or not? pics attached

If you follow the staight edge in your second pic out to the prop it looks to me like the wing is above the bottom of the hull y about 1.5 - 2 inches. On plane that would almost be breaking the surface wouldn't it?

 

[wired247]

Re: 150hp optimax installed to high or not? pics attached

Ive found prop centerline being about 4 1/2" below the keel give me the best compromise between running at higher speed and hole shot. Any higher than that and I sometimes ventilate off the start if I nail it. Lower and it gets harder to steer and top speed suffers. Note that 4 1/2" is about 2 inches over what I can mount it using the factory mounting holes. If I wanted just top speed I'd mount the prop center line about 1 1/2" below the pad and feather it off the start.

Your mounting is far lower than I would go.

IMHO mounting it so the anti cav plate is at water surface on plane is a recommendation I certainly wouldn't follow. That is super low and make the boat handle like crap and hard to steer over 50 MPH or so. The function of the anti cav plate is to prevent air getting into the prop at hole shot It is not to keep air out on plane. The anti cav plate shouldn't be any where near the water when the boats on plane.

 

[acuaholic]

Re: 150hp optimax installed to high or not? pics attached

Ok so, I finally got to go to the lake, weather was pretty nasty so I couldnt get out on the weekend, I can see the av plate when on plane, but with all the white foam and splashes I cant see how high it rides of the water, but its definatly no in line with water on plane, interesting thing is that I called the tahoe dealer like someone suggested and they told me that at the factory the motor is mounted in the third whole, so I am guessing the reason my motor has marks on the top hole is because someone must have thought it was to high up and lowered it and then didnt like the results and raised it back up. I did remove the hydrofoil and now I can trim up a bit before it caviates.
Now I dont know what to even think. Maybe just upgrade the prop.

 

[wired247]

Re: 150hp optimax installed to high or not? pics attached

Try the prop first. Some are terrible about ventilating. Some don't vent if they are piercing the surface.

 

[acuaholic]

Re: 150hp optimax installed to high or not? pics attached

Thank you very much, I will try to figure out the right one and order it here and let you know how it goes.