Re: [OMC-Boats] Engine RPM and Boat Speed

Hi Don,
 
Glad you were able to talk to Roy and get his explanation - - exactly
what I was trying to say last week.
 
>> This means my tachometer is reading a full 1,000 rpms below what it
should be on the higher end of the scale and is probably the primary
reason why I am going slower than normal. <<
 
The "lazy" tachometer in your boat explains away some of the
"strangeness" in your reported "RPM vs Boat Speed." Makes me wonder how
many of us are pushing dangerously high RPM's due to lazy, low-reading
tachs? (Eventually valve-train float will be the limiting factor with
the hydraulic lifters pumping up at ~5000 (true) RPM.
 
Replacing your tach is probably a good idea, but I'd venture to say it's
not "the primary reason why I am going slower than normal. <<
 
 

________________________________

From: omc-boats-bounces@...
[mailto:omc-boats-bounces@...] On Behalf Of Don Mandelas
Sent: Monday, July 28, 2008 12:27 AM
To: Evinrude & Johnson Boats of the 1960's and 70's
Subject: Re: [OMC-Boats] Engine RPM and Boat Speed

Well, Just to let everyone know.
 
Last week I followed Lee Schusters advise and contacted Roy Hansen who
owns an OMC certified repair shop in Salt Lake City. According to Roy
(and I'll relay this information as best as I can remember) a possible
reason why I may be traveling slower than normal at 3,500 rpms may be
that the Lower unit forward clutch hub and/or forward clutch spring may
have worn causing the hub not to engaged the propeller shaft fully. He
advised me that a new forward clutch hub/and or forward clutch spring
may be needed. He advised me that if I wanted, in order to save some
money, I could swap the clutch spring from the reverse hub and place it
in the forward hub (Since both hubs use the same spring on my lower
unit). I found Roys information very interesting and In the future I
may try replacing the forward hub and spring.
 
Also,

This weekend I was able to obtained a timing light and digitally measure
the revalutions per minute of my V-6 155 hp boat engine.
 
I discovered that when the timing light indicated 1,100 RPM's my boat
tachometer was reading 1,000 RPM's. And, when the timing light
indicated 4,000 RPM's my boat tachometer was reading 3,000 RPM's. This
means my tachometer is reading a full 1,000 rpms below what it should be
on the higher end of the scale and is probably the primary reason why I
am going slower than normal. I'll replace the tachometer and try the
boat again.
 
Thanks again for everyones help,
Don Mandelas
Washington State.
 
> ----- Original Message -----
> From: "Kenneth Fingerlos" <kenf@...>
> To: <omc-boats@...>
> Sent: Tuesday, July 22, 2008 9:03 PM
> Subject: Re: [OMC-Boats] Engine RPM and Boat Speed
>
>
> > Don -
> >
> > Please do let us know what you find out; I've got a 1968 Seasport-II
155
> > with similar issues; Slower than Lee's stuff says it should be and
I'm
> > running a 19" stainless prop. Seems like I've got plenty of power,
can't
> > run it at WOT because it'll over-rev, but really can't get above
30MPH.
> > Slippage somewhere sounds like a very interesting idea - had a car
once
> > with a bad clutch which behaved kinda similarly.
> >
> > Kenneth Fingerlos
> > Northern Idaho
> >
> >>>> On Tuesday, July 22, 2008 at 7:21 PM,
> >>>> <omc-boats-request@...>
> >> Message: 4
> >> Date: Tue, 22 Jul 2008 19:09:00 -0700
> >> From: Don Mandelas <dmandelas@...>
> >> Subject: Re: [OMC-Boats] Engine RPM and Boat Speed.
> >> To: "Evinrude & Johnson Boats of the 1960's and 70's"
> >> <omc-boats@...>
> >> Message-ID: <BLU118-W13EE6EF795282C3898E244DA840@...>
> >> Content-Type: text/plain; charset="iso-8859-1"
> >>
> >>
> >> Thank's Again everyone for your help and advice!
> >> You have given me some good ideas that could help fix my problem.
> >>
> >> Starting Tommorow morning I will look into the tackometer issue to
see if
> >> it
> >> is reading correctly,
> >> And, I will contact a qualified OMC repair man to see what can be
done if
> >> the forward clutch hub is slipping.
> >>
> >> And Thank you for asking, Yes, I am using Type C lower unit gear
lube.
> >> Don Mandelas
> >> Washington State.
> >
> > _______________________________________________
> > OMC-Boats mailing list
> > OMC-Boats@...
> > http://lists.ultimate.com/mailman/listinfo/omc-boats
>
>
> _______________________________________________
> OMC-Boats mailing list
> OMC-Boats@...
> http://lists.ultimate.com/mailman/listinfo/omc-boats

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Received on Monday, 28 July 2008