In regards to motor height......what are the affects of being too low.

[CRFan1]

I checked my motor height last night and the antiventilation plate is about an inch "below" the bottom of the boat. What are the actual disadvantages to this? More drag? Slower speeds? Less rpm? All of the above?

I have a 60 hp merc 4 stroke and it looks like I may need to go up a couple notches. What is the best way to actually move a motor up? You need an engine hoist I assume? It's a new boat....maybe I should tell the shop to do it?

 

[180shabah]

Re: In regards to motor height......what are the affects of being too low.

All of the above?

That about sums it up.

Talk to the dealer, ask why they mounted it SO LOW.... If they do raise it for you, pay attention to the process, you will likely move it 2-3 times before you get it just right.

 

[Tig]

Re: In regards to motor height......what are the affects of being too low.

My 50hp 4 stroke motor was 7/8s below. I raised it to 5/8s above. I was unable to measure any definite change in performance. (RPM, prop slip, gps speed) This defies what should have happened, but I can only share what I measured. The noticeable differences are that my aluminum prop can ventilate now if I turn hard, trim high or run WOT in rough water. There is also much less back spray at the stern.

I did not use a hoist to raise the motor. I trimmed the motor all the way in and supported the lower unit. I then removed the top two motor mount bolts and loosened the lower two. I then raised the trailer tongue with a trailer jack a bit at a time, checking to make sure that the motor was not stuck or binding. When I got it where I wanted, I replaced the top bolts lowered the tongue so that the motor was supported by the mounts. I tightened the bolts and sealed them.

 

[steelespike]

Re: In regards to motor height......what are the affects of being too low.

Raising a motor 2 inches can result in 2 to 3 mph increase in the extreme.
And a minimum change in the other extreme.Some props don't respomd well to increased height and others will allow a maximum increase.Usually a 4 blade prop does well and certain other props with cup etc resapond well to height.
When you increase speed you increase mpg.If a boat reaches a destination quicker
on the same throttle setting you save gas.Or if you can reach your old speed with less throttle etc.Also could be the difference of planing and not planing with a load.
I usually suggest raising to a point just before venting becomes a problem.
Some older style gearcases don't allow much height.E/J before through hub exhaust come to mind.

 

[Reel Kahuna]

Re: In regards to motor height......what are the affects of being too low.

...Talk to the dealer, ask why they mounted it SO LOW.... If they do raise it for you, pay attention to the process, you will likely move it 2-3 times before you get it just right.

Also, if it's a new boat, then you shouldn't have to pay them to raise it up :redface:

 

[Frank Acampora]

Re: In regards to motor height......what are the affects of being too low.

In addition, the engine being too low may cause water to rise up the leg and fill the splashwell.

 

[Outsider]

Re: In regards to motor height......what are the affects of being too low.

OK, I'll ask. Where is the cavitation plate in relation to the water when you're on plane? If it's at or below water level, you'll benefit from raising it. If you're slightly above water level, you're about right and may not see any benefits from moving it ...

 

[CRFan1]

Re: In regards to motor height......what are the affects of being too low.

OK, I'll ask. Where is the cavitation plate in relation to the water when you're on plane? If it's at or below water level, you'll benefit from raising it. If you're slightly above water level, you're about right and may not see any benefits from moving it ...

Well...that I have not checked yet Actually I am leaving in 1 hour for a trip to Minnesota for a week of fishing and I will get plenty of time to look at everything

Thanks for the all the advice guys!

 

[aussiejake]

Re: In regards to motor height......what are the affects of being too low.

here is mine at what I think is a good height for a mixture of calm and rough water. Propeller is a Mirageplus