6200 rpm too much?

[zenchal26]

getting 6200 rpm out of my 88 70hp evin it this too much? should I turn it down?

 

[CharlieB]

Re: 6200 rpm too much?

6200 is a little high, 5500 is almost ideal, but before you start changing anything you need to give us a lot more information.

What Boat
What prop
Is the prop hub slipping
Is the prop cavitating in turns
Did this recently start occuring

If this has always been like this then your prop may be slightly undersized/under pitched

Without knowing all the above it is difficult to make recommendations.

 

[zenchal26]

Re: 6200 rpm too much?

17.5 alum sea nymph. just got the boat, prop was pretty chiped up I filed the chips out so the prop is prob a litle smaller not cavitating. Is anything bad going to happen reving this high

 

[CharlieB]

Re: 6200 rpm too much?

We'd have to find "The Book" and look up the recommended operating range, MOST all outboard run right in the 5200 to 5500 range.

Many will run much more however ANY continued over-reving does shorten the time-life of internal parts, how long? Depends upon many things, in your case it really isn't a radical amount, just pull back on the throttle an eighth inch and run it. Sometime soon replace your prop but save this on as a spare.

 

[ezeke]

Re: 6200 rpm too much?

Crossflow engines are generally rated for full throttle operating range of 4500 to 5500 and generally set to top at 5500 to 5800 RPM at WOT.

Your motor is not a crossflow and is rated for full throttle operating range of 5000 to 6000 RPM. I think 6200 is about right at WOT for your motor.

 

[jay_merrill]

Re: 6200 rpm too much?

I agree that you should get a service manual for your particular motor, but I can make an educated guess that you will find that the WOT rpm range is 4500 - 5500 rpm.

There are a lot of opinions about this issue here at iboats, with some who have strong credentials in outboard mechanics, saying that the motors should be run over the manufacturers recommendations. I have a 1972 Johnson 65hp, which is a very similar motor to yours, especially in terms of the basic powerhead. I have had numerous conversations with my local OMC/BRP dealer about this issue, in regard to my both motor and other years/hp ratings - he is adamant that the max rpm should not be exceeded. His experience is thirty years as an OMC mechanic and dealer.

Given the differences in opinion, the best advice that I can offer is to surf this site and the web in general for opinions on the issue. After doing the reading, make your own decision on the matter.

 

[ezeke]

Re: 6200 rpm too much?

With little else changing, the powerpack on the 1989 70HP engine incorporates rev. limiting so that number cannot be exceeded. The limit is 6,700 RPM. on 1989 and more recent veersions of the 70HP motors, set by the powerpack.

You will find the "Full Throttle Operating Range" listed in the "Specifications" pages of your Owners Manual or your Service Manual. (That includes the 1972 65HP model).

 

[zenchal26]

Re: 6200 rpm too much?

I have a manual (selco not a very good manual if I do say so my self) just wanted some opinions. I beleve the book said around 5000. Thanks for the help guys.

 

[jay_merrill]

Re: 6200 rpm too much?

You will find the "Full Throttle Operating Range" listed in the "Specifications" pages of your Owners Manual or your Service Manual. (That includes the 1972 65HP model).

The 1972 65hp model WOT range is 4500 - 5500.

 

[ezeke]

Re: 6200 rpm too much?

That motor's range is not relevant to the subject matter of this thread.

However, there is no such listing as "WOT" in the "Specifications" pages of OMC model specific manuals.

WOT is an abbreviation for Wide Open Throttle, it is not a range.