raising OB motor

[Jigaman]

I have a 1999 1850 tyee with a 135 opti. I think it performs alright. ok holeshot and 45 mph with just me and running on fumes but usually around 42. My inlaws have a 2013 1875 crossover with a merc 150 4S which has good holeshot and runs upper 40's. When driving my boat I trim it up quite a ways before I find the sweet spot. When driving there boat I barely trim it at all and it blows out. How are these supposed to be set up? If I raised my motor one hole would I notice any better performance? Is theirs too high?

 

[Wild and Free]

I actually have a topic here about just this topic, here you go.

http://nodakangler.com/forums/showthread.php?598-Proper-outboard-engine-height&highlight=height

 

[catbird]

That boat needs a 150 on it. A 125 is way under powered. I get 51-52 out of mine with just me in it with a 150 yamaha

 

[shorthairsrus]

If it's a 1999 and its been running that way ever since why mess with it.

 

[Jigaman]

it is a 135,,, but I do wish it was a 150. It works fine though. I'm actually suprised how well it does on a boat that heavy. Just wondering if simply raising the motor a hole will gain some performance and also wondering if my inlaws motor needs to be lowered.

 

[Still_Learnin']

The performance you gain or lose is determined by a lot of factors. Motor height, like you mentioned, is one but so is the distance from of the nose of the gear case measured to the very back of the bottom of the boat, the pitch/diameter/make of the prop, water and air temperature, and a handful of other things. Seriously, an entire book can be written about it.

For the sake of taking a guess (and this is assuming that your in-laws are running the exact same boat with the exact same motor with the exact same prop as you; basically all measurements are the same with the exception on engine height) then I would say that lowering the engine would keep their boat from blowing out so much.

However, lowering the engine one hole is normally about a 3/4" adjustment. In most cases, a 1/4"-1/2" adjustment makes a significant difference in performance. It's entirely possible that lowering in just one hole will make it lose a lot of speed and possibly handle worse at top speed.

Is it possible that your in-laws carry more weight in the nose of the boat than you do? That is something that can greatly affect the top speed and contributes to blow out early into a trim cycle.

 

[Jigaman]

Good question. Similar size boats but different hulls. Not sure were the batteries are in their boat so weight in the bow could make some difference.

 

[Still_Learnin']

I'm sorry. For some reason I was thinking you both had the same boats.

Even so, the difference in hulls is probably the biggest factor. The way the water will come off the bottom of the boat and then how the lower unit and prop are able to "grip" that turbulent water is different with every hull and motor combination. It works off the same basic concept as a car or airplane with aerodynamics. There's a ton of variables that go into all of it. It's fascinating if you're like me and just like to go fast. But if not, I would say to leave well enough alone.