83 Merc 150hp I think its mounted to low

[drm11900]

Boat is a 78 Champion fish and ski 17-1/2' the motor is a 83 150 Merc...the problem I seem to still be having is exhaust getting up in the cowl. Well after a comparison to a similar boat at the ramp I realized my motor seems to sit lower in the water. I think what's happening is the exhaust ports in the mid section are getting under water at idle and causing it to get into the cowl making it cut out. My son helped me out tonight getting some pics. I noticed the cavitation plate is pretty low at half throttle.

What do you think?

 

[drm11900]

Re: 83 Merc 150hp I think its mounted to low

Here's a couple of videos. The first one is best towards the end. The second one shows whats going on with the exhaust.

http://www.youtube.com/watch?v=9LigkF8b1is
http://www.youtube.com/watch?v=lVw-NOuTOL0&feature=mfu_in_order&list=UL

 

[sschefer]

Re: 83 Merc 150hp I think its mounted to low

Yep, she's way low.. Throw a jack plate on it and you'll be a happy camper. A 5" offset should do the trick.

 

[drm11900]

Re: 83 Merc 150hp I think its mounted to low

Thanks Steve for the reply.

Going off memory I think there are five holes on the transom for vertical adjustment. I know I'm in the middle holes. Could I raise it to the bottom holes and avoid getting a jack plate?

Anybody else agree that it's to low in the water?

 

[circle hook]

Re: 83 Merc 150hp I think its mounted to low

what is the length from the edge where the engine sits on the transon to the bottom of the boat if its like 15 inchs you should need a short shaft engine and if you have a 20" model engine you will need to use a jack plate

 

[drm11900]

Re: 83 Merc 150hp I think its mounted to low

what is the length from the edge where the engine sits on the transon to the bottom of the boat if its like 15 inchs you should need a short shaft engine and if you have a 20" model engine you will need to use a jack plate

According to what you are asking I measure 24".

 

[gwukena]

Re: 83 Merc 150hp I think its mounted to low

Looks like your anti-ventilation plate is pretty well even with bottom of hull and you are running a stepped transom. Ideally anti-ventilation plate should be about 1" above bottom of hull. I imagine sitting at rest your exhaust ports are probably under water. Raise the motor up and try, you'll probably find boat handles totally different.

 

[gwukena]

Re: 83 Merc 150hp I think its mounted to low

Check this out http://www.marinepartsman.com/installing-an-outboard-on-your-boat.html, you could probably go even higher than 1" above

 

[Faztbullet]

Re: 83 Merc 150hp I think its mounted to low

That hull does not need a jack plate , it just needs to be raised a hole or two. If your using it to ski/tube with only go up a little . If your just fishing raise it at least 2 holes and you should be ok. If its a model 171DC it needs to be in 3rd hole and 24pitch trophy prop for max performance.....

 

[drm11900]

Re: 83 Merc 150hp I think its mounted to low

Not sure about the model but I am currently in the third hole.

We tubed once this summer and fished our butts off!

I'm gonna move it up tomorrow and hopefully test it out this weeked. Thing is Bow season starts Oct 1st and I'll be pretty commited to the tree stand after that but I'd love to get this wrapped up before I put it away for the season.

Thank you everyone for your imput. Much appreciated.

 

[FLATHEAD MAC]

Re: 83 Merc 150hp I think its mounted to low

LOOKING at your picture , cant tell if you have power tilt/trim. If not where is the manual tilt adjust pin (picture #3) , I SEE 4 adjustment holes and no pin?? could it have possibly broken off ??? Looks as if motor is trying to push under boat in (pict 1).

just courious.

 

[drm11900]

Re: 83 Merc 150hp I think its mounted to low

View attachment 116165View attachment 116163LOOKING at your picture , cant tell if you have power tilt/trim. If not where is the manual tilt adjust pin (picture #3) , I SEE 4 adjustment holes and no pin?? could it have possibly broken off ??? Looks as if motor is trying to push under boat in (pict 1).

just courious.

Power trim. In the first two pics above I was idling out of the no wake zone so it is trimmed down to keep the bow down.

 

[drm11900]

Re: 83 Merc 150hp I think its mounted to low

24pitch trophy prop for max performance.....

I do need a new prop but I'm holding off till I get the motor sitting right. I ran a 23P last weekend, I got 6000rpm at 54mph and a great hole shot. So I'm actually thinking a 24 might be what I want. Thanks for the input.

 

[Faztbullet]

Re: 83 Merc 150hp I think its mounted to low

Operating rpm for that engine is 5000-5500rpm. The reason you dont need a jack plate is that hull is stern heavy and setting it back will make engine even deeper in water due to transom angle. Then when you raise it, it will be back at the point you are at now.It may perform better on top end but that hull likes a lot of positive trim anyway......

 

[drm11900]

Re: 83 Merc 150hp I think its mounted to low

Operating rpm for that engine is 5000-5500rpm.

Curious how you get those engine rpm's.
The book I have tells me 5500-6000rpm. serial number on the motor = 6221419
If your numbers are right then I've been running hot all summer at 6000rpm WOT.

 

[drm11900]

Re: 83 Merc 150hp I think its mounted to low

OK raised the motor to the bottom holes(I was in the middle) and that's to high. It cavitates on the turn. Also the rpm's increased and I lost speed. So I'm gonna lower it to next to the bottom and see what that has to say tomorrow.

Thanks again for all the response. I do appreciat all the help. This is a great site.

 

[Faztbullet]

Re: 83 Merc 150hp I think its mounted to low

All 150's before 1985 serial number range 5203429 thru 6617369 rpms are 5000-5500, only the Magnum series starting at 6617506 is 5500-6000rpm. Even the newer Xr series are only rated at 5000-5600rpm range.

 

[drm11900]

Re: 83 Merc 150hp I think its mounted to low

All 150's before 1985 serial number range 5203429 thru 6617369 rpms are 5000-5500, only the Magnum series starting at 6617506 is 5500-6000rpm. Even the newer Xr series are only rated at 5000-5600rpm range.

DANG! Your right. I double checked my book and I was going by the V150 XR2. Now I suddenly realize my timing is off also. I gotta knock it back from 20 BTDC to 18 BTDC at cranking speed.

Thanks Faztbullet back to the garage I go.

 

[drm11900]

Re: 83 Merc 150hp I think its mounted to low

OK raised the motor to the bottom holes(I was in the middle) and that's to high. It cavitates on the turn. Also the rpm's increased and I lost speed. So I'm gonna lower it to next to the bottom and see what that has to say tomorrow.

Thanks again for all the response. I do appreciate all the help. This is a great site.

OK ran the V150 mounted next to the bottom holes on the transom. No cavitation, it handled well, had a nice hole shot. Most importantly it did run better on idle. Seems to have helped. Turns out I'm running an old predator prop and the pitch is all over the place. I had it checked. Two blades are roughly 22P and one blade is around 23P. So I'm gonna put a 24P on and get my rpms down Hopefully to 5600. Then all should be good.

Thanks again everybody for the help