Rev Limiter or slipping clutch>>

[rocket rich]

well guys and gals today is a new problem.. I put a friend in the front of the boat. we going along at about 4500rpm when the motor starts that bucking. All of the sudden the tack goes to
6240 rpm's??? I let off the gas and it took about 10-15 second for it to settle down. this is a new thing for this motor. Does this motor have a slip clutch? I remember years ago a Mercury motor that I had the prop would slip, but when I replaced the prop all was well??? How can I tell if this is a problem? I''m pulling at straws just trying to find the problems more than one???? The prop has a 7.5 on it,..

 

[Grub54891]

Mark the prop across the hub with a sharpie,run it till it does it again. Look at the marks. If they moved,it slipped.

 

[pvanv]

Yep. The F-N-R clutch is a mechanical dog, and unless damaged, cannot slip once properly engaged. If only partially engaged, it could possibly chatter. That would have rapid and severe results, and you would find metal fragments in the LU lube. At 6240 RPM, you are likely hitting the ESG (rev limiter), which is preventing you from blowing the motor apart. You may have a defective prop. If you mark across the hub and shaft, then go for a long WOT run, and the mark no longer lines up, the prop has slipped.

 

[rocket rich]

can you some how recommend a dealer with in a 75 miles I've ask the people that I bought it from the same question so far no reply. It surely felt like something was slipping like in the old days. I will try the deal with marking it crossways and see what it shows.. Right now we're in a rain mode for about three days. Also when ever I shift it , it does grind , but it always did it. Yesterday when we were going wot and it jumped up over 6200 from about 5400 it was already bucking.

 

[pvanv]

what is your ZIP code?

 

[rocket rich]

zip 63123

 

[rocket rich]

which prop is best 7.5 or 7.0and why

 

[Sea Rider]

It's not a which one is best, will depend entirely on your boat's weight, size and carrying load. To test props, engine must be in top running condition and a tach must be used to read max wot rpm, then you can go from there playing with prop pitches all you want.

Usually should test your combo with you alone and very lightly boat on flat no wind wind cond., if current prop gives top or near top factory stated wot numbers you are ok with that prop, if over revving must go for a + pitch. If engine has a rev limiter, it's a different story. Should go for one that doesn't kick in the rev limiter.

Happy Boating

 

[rocket rich]

Tell me what the difference is between the two prop 7.5 or 7.0 I don''t understand.My boat is the same every day , I never take any thing out of it.. I see where a certain web page has the 7.0 as the replacement prop.

 

[rocket rich]

computer acting up again

 

[pvanv]

zip 63123

http://www.tohatsu.com/dealersearch...y=Both&RADIUS=30&submit2=Search&NumHits=UnRun shows:

Company	Hetzler Bros. Boats
Address	3540 N. Hwy. 94
	St. Charles MO 63301
Phone	636-946-7888
Website	http://www.hetzlerboats.com
Distance	Approx. 22 Miles

and:

Company	Dori Marine Service
Address	801 N. State
	Freeburg IL 62243
Phone	618-539-9881
Fax	618-539-9882
Distance	Approx. 24 Miles

 

[pvanv]

Tell me what the difference is between the two prop 7.5 or 7.0 I don''t understand.My boat is the same every day , I never take any thing out of it.. I see where a certain web page has the 7.0 as the replacement prop.

The difference is pitch. There is a discussion of those pitches at http://www.tohatsu.com/accessories/prop.asp
There are many different props for the MFS8/9.8.
If you check the prop chart at: http://www.tohatsu.com/accessories/prop.asp
You will see that there are pitches from 5 to 9, and even two 4-blade high-thrust props as well. The short F9.8 comes from the factory with 7.5 or 8 pitch. If you need higher WOT RPM, reduce pitch. If hitting the ESG rev limiter, increase pitch or ease off the throttle a little.

 

[pvanv]

can you some how recommend a dealer with in a 75 miles I've ask the people that I bought it from the same question so far no reply. It surely felt like something was slipping like in the old days. I will try the deal with marking it crossways and see what it shows.. Right now we're in a rain mode for about three days. Also when ever I shift it , it does grind , but it always did it. Yesterday when we were going wot and it jumped up over 6200 from about 5400 it was already bucking.

Always engage the shifter briskly. Don't "ease" it into gear. If you allow a lot of chatter by going too slowly into gear, you get faster clutch and gear wear, and end up with metal particles in the LU lube.