Tach and Throttle Issues on Old Boat

[jgrote]

Well, I've been a boat owner for about a week, so it's time for things to start breaking. 1977(ish) Larson with 120hp Merc I/O. 1st issue I noticed when shaking it down was the tach is nowhere near accurate. It says I'm idling at 3000 rpm. Everything in this boat is original, so I know it's not a setup issue. I assume this is a bad tach?

Second issue is the throttle. There is no change in rpm until I get to about 90 degrees of movement. I can continue to push down on the throttle, but have to go to about 180 degrees to get to WOT. Do I adjust this at the carb, the control, or???

 

[Sea Rider]

Install a new tach, tachs don't last forever. Check there's no dead play between cable end and throttle linkage. At full hammer down all carb's butterflies should remain wide open. Readjust if needed...

Happy Boating

 

[jgrote]

I crawled under the dash to measure the tach, and found something a little surprising. The original tach has a date on it. 9/11/1968! This boat that was sold to me as a 1980, but actually seems to be a 1977, has a 1968 tach in it. I looked into the throttle a bit closer, and found it is actually working as designed. It moves that far to make sure it's fully engaged forward or reverse before it starts to rev. Some pics to show you what I'm working with.

 

[dwco5051]

Sounds like the purchasing agent for Larson my have ordered a crate of tachs and it took them a while to use them all up. Not a uncommon issue with boat builders as they use a lot of the same stock parts on many different models.

 

[mr 88]

What are the last two numbers on your HIN , usually located on the upper right hand of your transom , that will tell you the year it was built .

 

[jgrote]

What are the last two numbers on your HIN , usually located on the upper right hand of your transom , that will tell you the year it was built .

Which brings more mystery to this boat. The only number of any kind on this boat is a tag on the inside of the transom, behind the engine. I have read about this magical HIN, and it's supposed location, but there is nothing there, and no sign that it ever was. There are no signs of repairs, and the gel coat looks original. It came from a state that doesn't title boats, and I live in a state that also doesn't title boats, so there really is no history on this boat. The guy I bought it from said it was his FIL's boat from new. 3 years ago, he bought it from him and towed it down to where we live. Then he sold it to me. I researched the boat's numbers, the engine numbers, and what Larson offered in what years, and came to the conclusion that it is closer to a 1977 than a 1980. I still have found nothing on the internet to prove for sure.

 

[Captain Caveman]

What you can be sure of, is that you got a nice looking boat that is 40+ years old and still going strong.

As for the tach, it's also possible that it went bad at some point and the parts/repair shop only had older tachs sitting around for resale. You never know. That's a great looking boat.

You could call the North Dakota Game and Fish Department to track down info on the boat. It looks like that's where she was run for most of her life (at least until 2017), based on the North Dakota watercraft registration number and sticker on the side of the hull. They should have a record of the year, model, etc.

 

[mr 88]

Federal Law to have a HIN enacted for every boat built or imported into the USA since 1972 ,nothing to do with a particular state's law. So the stamp on the tach says 1968 , I would guess your boat is a 1968 -1971 built before HINs were required. Larson would not of side stepped that law.

 

[southkogs]

I think the styling and branding look closer to a early 70s model too. Great lookin boat either way!