Tach ?

[Pierutrus]

Hi all,
First off, what I'm dealing with.......
It's a 1996 Glastron SX195 with 4.3LX Mercruiser, Alpha 1 outdrive and a Ballistic 14-3/4" X 17" Pitch, 3 blade stainless prop.
The book say's WOT should be between 4400-4800.
When I'm flying at about 55mph or so, the tach is at 5800 or so.
Engine is sounding excellent. I've checked the back of the tach and it is set on 6, which I'm assuming means 6 cyl, which it is.
The original owner said he had the "original" stock prop that came with it replaced to something more that would pull his fat ***** out of the water. The guy was about 260 lbs. He said the shop pput the new one on and kept the old one. So I don't know what configuration it was. Would of been nice to have got it as a spare, but oh well.
Any suggestions would be most appreciated.
I don't think I'm hurting the boat.....Like I said...It just sings at WOT!

 

[QC]

Re: Tach ?

.
I don't think I'm hurting the boat

Yeah the boats probably fine . . .

It just sings at WOT!

I bet it does if that tach is right.

I would assume that the old prop was at least close, and if he needed more hole shot, then it is spinning faster than it was. I am struggling with 5800 RPM also, but you need to verify the tach is correct, if it is, then it is not the boat we're worried about

 

[Pierutrus]

Re: Tach ?

QC,
Thanks for the reply.
How would I verify the in-dash tach is working/reading correctly?
When I say boat, I mean it as a whole.....or hole.
Like the kind you throw money down in!
???

 

[Pierutrus]

Re: Tach ?

QC,
Also, I forgot to mention that the anode/stabilizer at the bottom of the drive was removed for (speculating), larger prop. There's only 7/8" clearance from the top of the prop to the bottom of the drive where it sits.
Thanks again

 

[Pierutrus]

Re: Tach ?

Yeah the boats probably fine . . .


I bet it does if that tach is right.

I would assume that the old prop was at least close, and if he needed more hole shot, then it is spinning faster than it was. I am struggling with 5800 RPM also, but you need to verify the tach is correct, if it is, then it is not the boat we're worried about

Would that mean.......possibly,
Larger prop, smaller pitch?

 

[Pierutrus]

Re: Tach ?

Anybody else with a reply...........

 

[John_S]

Re: Tach ?

Tach is most likely giving a false reading. I think your boat should have a thunderbolt 5 ignition, which has a rev limiter. Many tachs will drop back after tapping the glass. Also, could be picking up noise on the feed wire. Get a shop tach and hook up and compare.

A 55mph speed with a 17 pitch prop, in a 19' boat, sounds like a speedo reading and not GPS. Find out your drive ratio, and plug into a prop speed calculator. See if you have reasonable slip.

 

[fourwinnsdook]

Re: Tach ?

A 4.3 @ 5,800 = KABOOOOOM!!!!!!!!! not instantly, but sooner than normal.

 

[QC]

Re: Tach ?

Yeah, what he and John S ^^^^ said. I think the RPM number is wrong, the speed number is wrong and the pitch number may be too. I get negative slip numbers which is impossible. Need to verify RPM first, speed must come from a GPS, but we can at least answer your first question with the correct RPM . . .

 

[ricksrster]

Re: Tach ?

The 6 on the back of your tach might mean 6Pulse or 6P for a two stroke. It that is what is is try 3P or 3.

 

[Pierutrus]

Re: Tach ?

Thanks guys for all the replies and suggestions.
Will be taking her out next wednesday with the boy's this time and will get the specific's this time. Not what I remembered after the fact.
Will have GPS this next time. Have just ordered a 14 1/4 - 21 pitch alum prop (Hustler), to see if it brings down the RPM's into it's operating range. Hopefully, it will be here by the time we go out.
Start out with the 17 pitch, get readings. Switch to 21 pitch, see what changes.