Prop pitch and RPM'S

[kvwelch]

Good info in this forum. I have a 1985 Johnson 130. I replaced the 19" prop with a 24" Raker.(V-6 lower unit)At WOT i'm turning aroung 6000 RPMS. I feel this is excessive, but i've been told that a loop charged motor can stand the extra RPM's.I normaly stay at 5400-5600 just to be safe. Any input?

 

[DJ]

Re: Prop pitch and RPM'S

You are fine at 6K with a healthy engine that has been decarbed. <br /><br />The real point is that your engine is CAPABLE of 6K. THat tells me it is NOT overpropped.<br /><br />For decarb, see below.<br /><br /> http://forums.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000006

 

[Dhadley]

Re: Prop pitch and RPM'S

Sounds like its set up pretty good to me. 6K wont hurt that motor at all. They love rpm, that's why the limiter is at either 6200 or 6700 -- depending on which pack you have. <br /><br />BTW -- you dont have a V6 lower unit. It's the same size as a V6 and takes a V6 prop but the gear ratio is different. Thats why they call it a "V6 style" lower.

 

[reeldutch]

Re: Prop pitch and RPM'S

2 stroke engines are rpm engines thats how they get there horsepower.<br /><br />hp is a product of Torque and RPM.<br /><br />general 2 stroke outboards are no torque monsters. to get the hp needed(work) they have to have high rpm.<br /><br />if you can get 6000 rpm and your setup is efficient<br />no slip less then 85 your in great shape.<br /><br />if you ask the question what do mechanics see more:<br /><br />- cooked pistons at 5300 rpm(lugged)<br />- bearing failure at 5800 + RPM<br /><br />i think you will get 95 % for cooked pistons and 5 % for bearing failure.<br /><br />just check the efficiency of the rig setup.<br /><br />i can recomend reading a book from John flemming.<br /><br />"complete guide to outboard engines"<br /><br /><br />its not a shop manual its a book that go's into the mechanics, and theorie.<br />for a home mechanic who wants to know more its a great book.<br />you can find it on amazon.com<br /><br />i dont make any money promoting this book by the way.http://www.amazon.com/gp/product/18...3350-7168959?_encoding=UTF8&v=glance&n=283155

 

[kvwelch]

Re: Prop pitch and RPM'S

Thanks for the info. And I did not know about the decarbing. I will do it this week.

 

[kvwelch]

Re: Prop pitch and RPM'S

I missed a key stroke on the original question, it's a 1995 johnson 130 looped charged motor.

 

[reeldutch]

Re: Prop pitch and RPM'S

well you seem concerned about the amouint of rpms<br />your rig is at.<br />i think i answered that in the post above.<br /><br />good luck

 

[Dhadley]

Re: Prop pitch and RPM'S

We figured you had a 1985 120/140 or a late 90's 130. Either will live longest set up like it is. The V4 loopers love rpm.

 

[kvwelch]

Re: Prop pitch and RPM'S

I decarbed the motor last week with the seafoam mixture. I didn't realize how rough my motor was idling until after I ran the seafoam through it.It now purrs like a kitten. Thanks again for all of the posts.