Twin 175 Suzuki 4 Stroke eng height props and set-up

[v12mac]

Ok, I am looking for info specifically from folks who have experience with hanging Suzuki twin 4 strokes. I know all the old standard tricks about props and motor height, what I am looking for is specific firsthand experience with these motors and how they like to run on a hull. With the lower gear ratios and huge props I want to know if any of the conventional rules of hanging a set of motors changes.

What I have 1992 Mako 261 with twin Suzuki 175?s spinning 16?x21.5? props.

I am happy with the overall performance but I think there is more?

Some info, the motors are mounted so the inside of the anticav plate is above the bottom of the hull, the center is right at the bottom of the hull and the outside is under the bottom. The boat runs 48mph now but I really have to trim the motors to the sky to get up 5950 RPM and if I back off the throttle any at that trim the boat wants to bounce.

Here is the strange thing.. I get 3mpg with perfect conditions and a light load at 32mph but if I run on one motor and kick the other up and run flat out I get 32 mph and 3.22mpg. How is that possible?

Questions:

Am I over Diameter / Pitched on the props?
How much if any do the motors need to come up?
Why am I getting better econ on 1 eng I know there is less drag but this is contrary to what everything I have ever read about twin eng set-ups?
Why do some prop charts say that the 16??s are for 200-300hp only?

Thoughts?

 

[v12mac]

Re: Twin 175 Suzuki 4 Stroke eng height props and set-up

I think I am going to go up 2 holes

 

[reeldutch]

Re: Twin 175 Suzuki 4 Stroke eng height props and set-up

you should be able to easily reach 6000. witch a light load. Empty boat low fuel.

if it doesnt i would not change the hight of the engines, i would reprop the motors.

when you change the hight you have a bigger chance of blowing out in turns and loose waterpresure.


i would prop the motors when the boat is empty at 6200 rpm just not hitting te rev limiter.

so when you put a full tank of gas in it and fill up the coolers and livewells and have 4 people on board with all the gear you can stuff in the boat, it would still run around 5800/6000 (heavily loaded.

in this scenario with your motors jacked up 2 wholes it will slip and slip and slip.

jacking up engines is mosltly for light boats that have props that can run shallow or a 4 blader.
lift the boat quick out of the water.
Im shure thats not what you are looking for.

if you use the boat just by yourself 5950 is not bad if this is the everage load.

 

[reeldutch]

Re: Twin 175 Suzuki 4 Stroke eng height props and set-up

on the fuel economy

what rpm are you running the 2 engines at 32mph

what rpm are you running only 1 motor at 32 mph


compare that to the chart.

looks all right to me

 

[v12mac]

Re: Twin 175 Suzuki 4 Stroke eng height props and set-up

Thanks for the reply, this link has several shots and videos of how the boat runs / rpm and econ at var speeds.


http://www.classicmako.com/forum/topic.asp?TOPIC_ID=26465

 

[reeldutch]

Re: Twin 175 Suzuki 4 Stroke eng height props and set-up

if you spend 25.000 dollars on engines and rigging i'm sure they will let you try 19 pitch props.

give it a shot before changing engine hight.

 

[v12mac]

Re: Twin 175 Suzuki 4 Stroke eng height props and set-up

" if you spend 25.000 dollars on engines and rigging i'm sure they will let you try 19 pitch props.

give it a shot before changing engine hight."

You would think so but their answer was and I Quote " If I let you try any of our props they are used as soon as they touch salt water"

When I picked the boat up from the repower they said "Oh it just jumps right up to 6K no problem"

I am going to the other dealer in town Monday to have them take a look.