Another Mercury Question - SailNet Community
 
LinkBack Thread Tools
post #1 of 7 Old 01-16-2005 Thread Starter
Junior Member
 
Join Date: Sep 2001
Posts: 28
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Another Mercury Question

I am trying to figure out what the OEM pitch is on my 1998 2 stroke 1998 outboard. Also, I am trying to figure out if changing the pitch will affect the "power" of the prop. I have no concern about "top speed" I want "pushing power." I have it installed on a 26'' Columbia and hate running it at or near full throttle. I guess that really means, can I change the prop and get the same or more push at lower RPM''s?

I have tried the Mercury website, but they only have a prop selector for go fast boats.

Thanks.

Rich
dirtchickn is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of 7 Old 01-18-2005
Member
 
Join Date: Nov 2002
Posts: 57
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 13
 
Another Mercury Question

Top end speed loses low end power, low end power loses top end speed. Prop pitch is typically matched to allow the motor to operate at its optium rpms. Why not try taking the prop to a prop shop and talk to the guy, they can typically adjust the cups and pitch 1-2 degrees by repressing it.

If you are running it wide open I would venture to say you are concerned about top end speed
Yodagwb is offline  
Quote Quick Reply Share with Facebook
post #3 of 7 Old 01-18-2005 Thread Starter
Junior Member
 
Join Date: Sep 2001
Posts: 28
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Another Mercury Question

Not necessarily. I just want to move my sailboat at a reasonable speed. I have no choice but to run at full throttle to move on windy days, hence the question about props. I am hoping to figure out a way to get more push at lower rpms. Maybe my logic is wrong, but shouldn''t that be better for the engine?
dirtchickn is offline  
Quote Quick Reply Share with Facebook
post #4 of 7 Old 01-18-2005
Senior Member
 
RichH's Avatar
 
Join Date: Jul 2000
Location: Pennsylvania
Posts: 3,545
Thanks: 24
Thanked 165 Times in 154 Posts
Rep Power: 16
 
Another Mercury Question

You want to be able to run at the maximum rpm so that you develop maximum horsepower when needed for ''emergencies'', etc. Running under heavy load at reduced rpm will result in rapid engine wear --- especially the piston wrist-pins and piston rings/cylinder walls. If the hydrostatic clearances in the bearing journals have already become worn you tend to risk ''crashing'' the crankshaft journals against the bearings due to the ''extreme'' cylinder pressure that the oil (pressure) in the bearings have to support. A ''lugging'' engine is prone to ''blow'' head gaskets frequently (and sometimes bending a crankshaft). Running at high load and low rpm is called ''lugging'' ---- Not good for the engine. Look at the "power curve" for your engine: rpm vs. developed horsepower.
F
or long life at your ''normal cruising'' speed try to obtain 75% - 80% of max rpm by adjusting pitch, etc. of the prop --- that will leave an extra 20-25% rpm for ''emergency'' conditions (huge chop, windblown, etc.). If you cant obtain maximum rpm or cant come ''close'' to maximum rpm with your current prop, this indicates that you should consider to ''re-pitch'' the prop so that you can.

A diesel''s ''clearances'' are usually set-up for ~75% of max. rpm to gain maximum service life; running on either side of that value will usually result in shorter service life.
;-)
RichH is offline  
Quote Quick Reply Share with Facebook
post #5 of 7 Old 01-19-2005
Member
 
Join Date: Nov 2002
Posts: 57
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 13
 
Another Mercury Question

Two stroke motors are designed to run at high rpm''s, un like 4 stroke. Prolong low rpm operation in a two stroke is not good for it. If you contact merc they can probably tell you what the optium or top rpm operation is, and then if necessary adjust the prop to achieve that target. If your boat is not able to achieve a reasonable operating speed given the proper engine rpm''s your dealing with a under power issue, in which case no prop in the world is going to correct that.
Yodagwb is offline  
Quote Quick Reply Share with Facebook
post #6 of 7 Old 01-20-2005 Thread Starter
Junior Member
 
Join Date: Sep 2001
Posts: 28
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Another Mercury Question

And that''s is unfortunately the problem. I have 8 hp to push 5800 lbs. I get where I want (in and out of the marina) by motorsailiing mostly. I have the advantage (and diasadvantage) of being in a really protected marina. Unfortunately, I cannot ever sail in or out, but by leaving the main up and motoring I catch every last little bit available, hopefully making life easier on the engine. I worry b/c I have really shallow water (the seagulls stand on the bottom)on either side of a 1000 yard channel. Should the motor die, I''m going aground.

I am trying to figure out, short of replacing the outboard, if anything can be done outside of the factory prop to make life better.
dirtchickn is offline  
Quote Quick Reply Share with Facebook
post #7 of 7 Old 01-20-2005
Senior Member
 
Join Date: Mar 2000
Posts: 119
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 16
 
Another Mercury Question

If you can''t find a satisfactory fix,have a stern anchor ready to deploy in an instant.
geohan is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Another proper course question langousta Racing 11 12-27-2005 05:33 AM
Mercury 25 4-stroke dlschilke24 Gear & Maintenance 0 05-25-2004 06:31 AM
Embarrasing Question, what in definition is a charter? KainX General Discussion (sailing related) 4 07-21-2003 03:43 PM
Glassing Question pirateofcapeann Gear & Maintenance 6 05-29-2003 02:58 AM
A question to all boat owners Apollo18 Crew Wanted/Available 6 12-31-2001 08:14 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome