Speedometer registering 15 MPH at top speed

[sped]

The speedometer on my 1996 Mercruiser 5.7L with Alpha One drive operates poorly. It does register, but only 15 MPH when I am doing 45 or so.
I have looked for a pedo tube but it does not have one. Where is the speed pick-up location? In the outdrive?? Anyone know how to clean it out?
Regards,
Ed

 

[Don S]

Re: Speedometer registering 15 MPH at top speed

Look on the leading edge of the lower unit. There is a hole in it for the speedometer pickup.

 

[sped]

Re: Speedometer registering 15 MPH at top speed

OK found the hole, now what do I do to fix it? Should I take a stick and put it into the hole or blow it out with compressed air? I can not see anything plugging it.
Ed

 

[Bondo]

Re: Speedometer registering 15 MPH at top speed

Ayuh,...........

Start Inside the Boat,+ Work your way Out to the Pitot Hole in the Lower Unit..........

 

[sped]

Re: Speedometer registering 15 MPH at top speed

OK Thanks, I found two things that may be trouble, first I found a tie strap that was very tight, cutting off any pressure sent. Second a little plastic coupling on the out-drive that seems to be deteriorated. I put the coupling back together and cut the strap. I will replace both.
Regards,
Ed

 

[180shabah]

Re: Speedometer registering 15 MPH at top speed

Merc redesigned the connector, I assume the new ones work better? you may want to look into getting the new one.

They are not expensive (6-7 bucks), I need to replace mine to match the new lower unit I replaced last year, just haven't got around to it.

 

[andy1canada]

Re: Speedometer registering 15 MPH at top speed

Howdy!

Okay Dudes, listen-up!

I'm surprised at Don and the boy's for missing this one.

ALWAYS start with the easiest possiblilities for a solution, then work through - in order of difficulty - till you find the problem.

Two things with Sped's slow-going 350' jumped out at me immediately:

1) Did you remember to un-tie the boat from the wharf? (I know from experiance that it is nearly impossible to pull a skier out of the water with the wharf still attached)

2) If your boat is a trailer-boat, be certain after you launch that the trailer is not still attached beneath the boat. (This situation can cause severe loss of top-end speed; however, it does make it easier on the boat if you need to beach her on a rocky shoreline...)

Hope this helps.
Happy boatin'...

Terry