Marine: Boating, Sailing, PWC, GPS and Navigation - Is it possible to install a tach on an outboard?

Ok heres the situation, I have a 15, slyvan, with a 95 28 hp johnson. I have installed a carpeted wood floor that dropped my speed from around 28 mph to 24 mph. 4th of july weekend we had alot of rain and the carpet and wood got saturated. I tried pulling my neice on a tube (50 lbs) and I couldnt get on plane. I know its a small motor, but have alot of younger kids in the family that love to tube, and I have the only boat. My prop is a 9.2 x12 pitch, I just got that fixed from the shop(welded and repitched) well they offered me a used prop that someone dropped off to get reworked. I asked them about my problem and they suggested dropping the pitch of the new prop to a 9.2 x 10. during a load(tubing) it may help get out of the hole, but im worried about overrevving the motor. With the 9.2x12 with just me in the boat, it gets on plane in a heartbeat, even with another passenger it does good, and when full throttle it screams. They say when you drop a pitch, which actually I am dropping 2, they say you add 200 rmp per pich change. Im worried about blowing the motor. Any help would be appreciated. he going to change the pitch of the new prop tommorow, and if I want it back to the normal 9.2x12 it will cost me another 30$, so even then its still cheaper then buying a new prop. Any thoughts, or am I just worried for nothing?

Its good you are concerned about the rpms, you can cause damage to the powerhead if you overrevv it.
The tach is driven off the charging circuit. If you have an electric
start engion then you have a charging circuit.
The tach lead is in the loom leading to the control box with the key switch.

Thanks for the info, I have an extra connector at my throttle controlstarting key mechanism. It has a weird plastic plug end on it that has either 2 or 3 terminal in it, it is also a male plug if that helps. Are we talking about the same thing possibly. I wish we could attach pics to the messages......ugh

yes that is the extension harness plug, you can order the harness
and attach a tach to it.
I will try to locate a p/n for you.
scott

Whats the thoughts on the 20$ digital tachs, that have leads that appears to attach to the spark plug or cable, not really sure. I found a tach and harness at cabelas, but for both im looking at 80 bucks plus shipping, and they cant tell me what the plug lookslike, so Im not 100% sure if it will work, they do carry like I said the digital kind, any thoughts?

here is a link the the website and discription of what I am talking about, its a long one.......lol.... ps any idea on what rpm my boat should run at full throttle,And idle. I dont want to over do it:)
http://www.cabelas.com/cabelas/en/templates/product/standard-item.jhtml?id=0015240015383a&navAction=push&navCount=2&indexId=cat21320&podId=0015240&catalogCode=ID&parentId=cat21320&parentType=index&rid=&cmCat=MainCatcat21276

The part number you want is 174732 it connects the omc
or medallion or other tach to the control box, about 12 bucks.