View Full Version : Suitable Outboard

31-12-2001, 06:52 PM
I have a 4.1 meter fibaglass pride runabout with a 20 hp mercury that i use to fish the estuaries. the boat won't plane with the 20 (seems to cavitate ) tried to change the angle of the motor, no gains there. the prop is a 9p A4 if that was changed would it help, or is a bigger o/board the real answer. the boat shop that the boat was purchased from said that the 20 would be fine, i think he was telling half truths. If another o/board was purchased what is the max for a boat like this

01-01-2002, 01:25 PM
I use to have a steber 455RA witha 50 johno on the back. It did a bout 28 knots and was perfect. The hull was rated to 100 hp. With your hull a new or reconditioned 40 should be just about perfect. Don't put anything over 60hp on the back though.

03-01-2002, 05:49 AM
there should be a plate on the boat somewhere stating the max hp of your type of boat . it also should tell you the weight of the boat and no. of passengers allowed . if it's cavitating then can the motor sit lower on the back of the boat ? so the prop sits below the bottom of the hull as not to get the prop out of the water . if that fails then try and borrow a different type of prop to try before buying another one . if all else fails then a bigger outboard is the answer , but try the others first and then try for a test drive on a hull similar to yours so you will see what is best for your needs

03-01-2002, 06:29 PM
Thanks for the advice, can't read the plate with max out board size ( I think its 75 but not sure) prop siting in the right position, sound like a new prop or another outbourd

07-05-2006, 10:27 AM
Just looking back through the archives to see where it all started .... looks like you were a stalward of Ausfish Blaze....

Do you have shares in the company yet??? ;D ;D ;D

ps did you fix the problem??



07-05-2006, 11:10 AM
Sorry if this is off topic but why under Started by on the main page does it say blaze (Ex Member)?
:o :o :o :o :o :o :o :o :o :o :o :o :o :o :o :o :o :o :o

07-05-2006, 11:29 AM
Maybe he got the big "B"


07-05-2006, 11:35 AM
OH so long ago
funny it come up, the boat still sits out at our local marine shop, I traded it in on a sounder of all things, bare hull on a trailer (frame with a set of wheels). Their plan was to put a 75 - 100hp on the back and sell as a ski boat when they traded a suitable outboard. If you seen it now you would be amazed at how a boat deteriates over a few years of no use. Only suitable for the tip now I would think.

08-05-2006, 07:04 AM
Did you ever come right with your glass runaround - I have a lovely 40HP mariner (1990) if you up for it (2 if you like).

Will trade one for a year's subscription to Private Boat and Outboard repair lessons by selected Ausfish Members


08-05-2006, 07:36 AM
Hi Mike
first stage was a 25hp tiller, converted to foward control, this plained the boat fine but with the need for speed that was updated to a 70 evinrude (had plenty of speed then)
Mike have you ever thought of doing a basic small engine/outboard basic mechaniclly course, by the way you are not doing a bad job at what you are doing now with the outboards.

08-05-2006, 10:50 AM
Cavitation is generaly caused by having the motor too high on the transom Your cavitation plate should be about an inch below the transom bottom.. try that.. and you will find the 20 HP motor will pull up with a little trim adjustment...


08-05-2006, 10:59 AM
As most of you know when trimming ob towards the transom it will lift the bum up and plane up to certain speed then it will dig its bow -- which will reduce the speed and the performance becomes unstable..... look for the happy Medium


08-05-2006, 11:05 AM
As marlin would say you will have NO such problems with a CAT ;D ;D


08-05-2006, 09:02 PM
Ahoj, is it not you that says that ???
Pete well he would love to say that but , lets get the colour sorted first.
best luck..

09-05-2006, 05:10 AM
Mike have you ever thought of doing a basic small engine/outboard basic mechaniclly course, by the way you are not doing a bad job at what you are doing now with the outboards.

Gee Thanks :-[ :-[ :-[

I have thought about such a course - not found one yet. I'm sure I will though.