prop pitch/rpm and trim?
 

I was on the lake tonight and doing some RPM testing and something
doesn't seem right. The lake was calm and I've got a 4.3L 190HP
Mercruiser on an 18' bowrider (about 2500lbs). The engine is rated at
4400-4800 RPM. The prop is a 14x23P. The literature states that the
boat should hit about 52MPH. Granted, the gauge on the boat might not
be entirely accurate, but I was only able to get about 45MPH running
pretty close to 5000 RPM. I was trying to modify the trim, but mostly
was running about in the middle (if that means much to anyone) - trim
level. I am going to do some more testing, but my initial thoughts
are that I need to go up one degree? To a 24? Is there something
that I could be doing wrong to get these results?
Thanks for any help!

prop pitch/rpm and trim?
 

Trim all the way down and go WOT. Then when cooking start to trim up for
max speed / rpms. If the boat starts porposing or the outdrive cavitates you
went too far so rinse and repeat.

Once you *find* max note the RPM's - if it's over 5000 you could prolly go
up a pitch. If you have aluminum prop @ 23 you should go to a 25 stainless.
If it's a stainless 23, have a prop shop make it a 24.

Remember going up in pitch will hurt your holeshot a bit.

Borrow a GPS for best speed measurements.

-W


--

PLEASE NOTE: Email address change from to

"werlax" wrote in message
om...
I was on the lake tonight and doing some RPM testing and something
doesn't seem right. The lake was calm and I've got a 4.3L 190HP
Mercruiser on an 18' bowrider (about 2500lbs). The engine is rated at
4400-4800 RPM. The prop is a 14x23P. The literature states that the
boat should hit about 52MPH. Granted, the gauge on the boat might not
be entirely accurate, but I was only able to get about 45MPH running
pretty close to 5000 RPM. I was trying to modify the trim, but mostly
was running about in the middle (if that means much to anyone) - trim
level. I am going to do some more testing, but my initial thoughts
are that I need to go up one degree? To a 24? Is there something
that I could be doing wrong to get these results?
Thanks for any help!

prop pitch/rpm and trim?
 

Your underproped


--
Bruce
99 White WJ 4x4 Select Trac
89 YJ
03 Liberty Ltd L.O.S.T #000256
90 XJ6 Sovereign

"werlax" wrote in message
om...
I was on the lake tonight and doing some RPM testing and something
doesn't seem right. The lake was calm and I've got a 4.3L 190HP
Mercruiser on an 18' bowrider (about 2500lbs). The engine is rated at
4400-4800 RPM. The prop is a 14x23P. The literature states that the
boat should hit about 52MPH. Granted, the gauge on the boat might not
be entirely accurate, but I was only able to get about 45MPH running
pretty close to 5000 RPM. I was trying to modify the trim, but mostly
was running about in the middle (if that means much to anyone) - trim
level. I am going to do some more testing, but my initial thoughts
are that I need to go up one degree? To a 24? Is there something
that I could be doing wrong to get these results?
Thanks for any help!

prop pitch/rpm and trim?
 

What type prop are you running. If it s an aluminum 23 then it may not be a
23 anymore. Take the prop to a prop shop and have them measure it. This
will let you know for sure what you need.
My guess is a good SS performance prop in a 23 is what you really need and
your prop is not a true 23 anymore. Check out the Mirage Plus from Merc.


Tony

"werlax" wrote in message
om...
I was on the lake tonight and doing some RPM testing and something
doesn't seem right. The lake was calm and I've got a 4.3L 190HP
Mercruiser on an 18' bowrider (about 2500lbs). The engine is rated at
4400-4800 RPM. The prop is a 14x23P. The literature states that the
boat should hit about 52MPH. Granted, the gauge on the boat might not
be entirely accurate, but I was only able to get about 45MPH running
pretty close to 5000 RPM. I was trying to modify the trim, but mostly
was running about in the middle (if that means much to anyone) - trim
level. I am going to do some more testing, but my initial thoughts
are that I need to go up one degree? To a 24? Is there something
that I could be doing wrong to get these results?
Thanks for any help!

prop pitch/rpm and trim?
 

"Tony Thomas" wrote in message news:1JjQa.53501$ye4.40177@sccrnsc01...
What type prop are you running. If it s an aluminum 23 then it may not be a
23 anymore. Take the prop to a prop shop and have them measure it. This
will let you know for sure what you need.
My guess is a good SS performance prop in a 23 is what you really need and
your prop is not a true 23 anymore. Check out the Mirage Plus from Merc.

Yep, it's an aluminum. It's the prop that came with the boat. I've
been told that I should have another prop on the boat for emergencies.
I was considering taking this prop off and using it as the spare and
getting myself a SS one. Thanks for the recommendation. Are all SS
props in the same price range? I haven't started researching them
yet.

Thanks!

prop pitch/rpm and trim?
 

"Clams Canino" wrote in message news:aAdQa.47033$GL4.11297@rwcrnsc53...
Trim all the way down and go WOT. Then when cooking start to trim up for
max speed / rpms. If the boat starts porposing or the outdrive cavitates you
went too far so rinse and repeat.

That is basically what I did. It sounded to me like the engine was
whining a bit so I tried trimming down but it didn't change the engine
sounds much. I wasn't able to affect the top end speed by trimming.
The only thing that changed was the RPMs.

Once you *find* max note the RPM's - if it's over 5000 you could prolly go
up a pitch. If you have aluminum prop @ 23 you should go to a 25 stainless.
If it's a stainless 23, have a prop shop make it a 24.

Remember going up in pitch will hurt your holeshot a bit.

Yeah, considering that the lake I most frequent has a speed limit of
40 will be a large consideration. I will be mostly pulling
tubers/skiers. Since this boat is new I just wanted to do some
testing and make sure that I'm doing it right.

Borrow a GPS for best speed measurements.

As soon as I scrape up the cash I will be replacing my fishfinder with
a fishfinder/GPS.

Thanks for the tips.

prop pitch/rpm and trim?
 

All SS props are not the same and are not priced the same. You can get a
Michigan Wheel for a lot less but that is exactly what you have. Basically
an aluminum prop design made out of SS. Not worth the money.

Since you stated that you are maxed out at 40 mph (speed limit) wise, I
would definetly go w/ a good 4 blade prop or even the high 5 (more expensive
but best for pulling) to maximize hole shot/acceleration for skiing.
There is a high five on ebay right now
http://cgi.ebay.com/ebaymotors/ws/eB...m=2422854 236

Tony

"werlax" wrote in message
om...
"Tony Thomas" wrote in message
news:1JjQa.53501$ye4.40177@sccrnsc01...
What type prop are you running. If it s an aluminum 23 then it may not
be a
23 anymore. Take the prop to a prop shop and have them measure it.
This
will let you know for sure what you need.
My guess is a good SS performance prop in a 23 is what you really need
and
your prop is not a true 23 anymore. Check out the Mirage Plus from
Merc.

Yep, it's an aluminum. It's the prop that came with the boat. I've
been told that I should have another prop on the boat for emergencies.
I was considering taking this prop off and using it as the spare and
getting myself a SS one. Thanks for the recommendation. Are all SS
props in the same price range? I haven't started researching them
yet.

Thanks!