Reply
 
Thread Tools Search this Thread Display Modes
 
Old 06-02-2020, 01:26 PM   #1
Ensign
 
Join Date: Jun 2020
Posts: 3
Default New member

Hi all I just purchased a 1998 37 FT Maxum SCR and was wondering can anyone tell me what the factory Prop sizes were, I have twin 7.4 MPI Mercruisers 330 hp and want to make sure the props I am running are correct as I have seen some issues relating to throttle and RPM that are not making sense, my driver is going to get me the prop info later this week but wanted to know the stock size for this size of boat.

Thank you
__________________

ron f is offline   Reply With Quote
Old 06-02-2020, 01:33 PM   #2
Moderator

 
Join Date: Apr 2008
Posts: 4,927
Default

What is your Max RPM at wide open throttle (WOT)? Do you know the pitch of the props on there now?
__________________

shrew is offline   Reply With Quote
Old 06-02-2020, 01:39 PM   #3
Ensign
 
Join Date: Jun 2020
Posts: 3
Default

do not know pitch, 4000 rpm on stb and cannot get more than 3300 on port
ron f is offline   Reply With Quote
Old 06-04-2020, 01:42 PM   #4
Moderator

 
Join Date: Apr 2008
Posts: 4,927
Default

4400-4800 is the range for Max RPM. I can see why you're concerned. Unless you have two different props, which is unlikely, you have some other variable at play here.

Is this an Inboard or an IO?
Gas or Diesel?
shrew is offline   Reply With Quote
Old 06-04-2020, 01:47 PM   #5
Ensign
 
Join Date: Jun 2020
Posts: 3
Default

Quote:
Originally Posted by shrew View Post
4400-4800 is the range for Max RPM. I can see why you're concerned. Unless you have two different props, which is unlikely, you have some other variable at play here.

Is this an Inboard or an IO?
Gas or Diesel?
ok i just had my diver chk yesterday and i have 21R20 4 blade props motors are 7.4 330hp mercruiser mpi gas inboard and my max rpm range is 4000/4400 couple of other folks i have spoke with are running 21x23 or 21x24
ron f is offline   Reply With Quote
Old 06-04-2020, 05:01 PM   #6
Lt. JG
 
Join Date: Mar 2017
Posts: 19
Default

If you have IO, and assuming tach’s are correct, you may want to check for a spun hub. If you start throttling up to get on plane and one engine feels like it “breaks free” while the other labors, then the spun gun would be on the higher RPM engine.

I had a similar experience when I purchased my boat. Unfortunately the survey was done lightly loaded and it didn’t slip until the boat was normally loaded for our first weekend. The slipping engine would wind up to normal RPMs and the good prop would labor and the boat would barely get on plane.


Sent from my iPhone using Tapatalk
yahoo82 is offline   Reply With Quote
Old 06-04-2020, 05:02 PM   #7
Lt. JG
 
Join Date: Mar 2017
Posts: 19
Default

Sorry. I missed your latest post where you specified inboards. Disregard.


Sent from my iPhone using Tapatalk
__________________

yahoo82 is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not 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 Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Powered by vBadvanced CMPS v3.2.3

All times are GMT. The time now is 04:48 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2020, vBulletin Solutions, Inc.