Reluctant 70hp but then vroom...

[Swivelhart]

I think I already know that the answer to my question is the need for a good carb cleaning but I will describe the symptoms anyhow! I just put my boat on the lake for the first time after buying it. It sat for two years but fired up in my yard almost immediately and idled great. After pushing off from the dock with my family it idled beautifull but refused to throttle up...just kind of bogged a little. I putted around like this for about 10 min. Just before deciding to put back to the dock I turned around and saw my wifes look on her face that said "you bought another junker!" eerrrgghhh...Then I thought maybe if I move the throttle up and down a few times it might do something. After about 10 up and downs all of a sudden the engine revved and started pushing the boat along nose up but would not plane out. I thought to myself oh boy probably a bad motor with bad compression. All of a sudden I felt the boat pick up speed as it planned out and ran awsome...pretty fast, much faster than I expected. It would only run good at upper throttle. If I came to a stop it would idle great but would not throttle up smooth unless put the lever up and down again...then it would rev but would take a minute or two to plane out. Once on plane it ran awsome!!! It is a 16ft glastron with 70hp. When on the lake it was me 170lbs, wifey 135lbs, daughter 125lbs, son 60lbs, other son 40lbs, and toddler 25lbs. Any hunches let me know thanks.

 

[eavega]

Re: Reluctant 70hp but then vroom...

What year is your motor? There was a technical service bulletin put out about the 1976 70 hp Johnson regarding poor mid-throttle response. It will idle all day long, and run WOT without an issue, but it had very poor mid-throttle. The TSB has instructions for carburetor modification that would help the issue. This only affected the 1976 70 hp from what I read.

Rgds

 

[Swivelhart]

Re: Reluctant 70hp but then vroom...

And to that response my motor is indeed a 76. That is strange! I wonder where I could find the directions for carb modification. Any idea?

 

[Swivelhart]

Re: Reluctant 70hp but then vroom...

Do you still have a copy of the TSB and drilling info? I have never done that before. Also, how does this problem develop? There is no way they could have supplied these motors from the factory with this issue!

 

[eavega]

Re: Reluctant 70hp but then vroom...

Check your PMs. Problem developed from manufacturing apparently. Just like when a vehicle manufacturer issues a recall. Johnson corrected it in subsequent model years. My thing was how could a motor from 1976 make it to 2011 without this manufacturer-recommended modification having been performed. It can and has happened, though, since it happened to me. When you read through the mods, you will find that there is a very easy way to tell if your carbs have already been modified, so I was sure that mine were not.

Good luck, and let us know if it works for you.

Rgds

 

[Swivelhart]

Re: Reluctant 70hp but then vroom...

thanks I just sent you an email. I hope this fixes the problem and I agree about how a motor could make it so long without the mod. Scratching my head on that one!

 

[Swivelhart]

Re: Reluctant 70hp but then vroom...

Thats a nice yarcraft you have. Do you still have it? I heard these motors are great motors, and strong. I am also glad that I read some posts first without replacing a bunch of stuff I dont have money to spend on at the moment!

 

[eavega]

Re: Reluctant 70hp but then vroom...

Have not received your msg. I most certainly still have my yar-craft. It's a perfect little boat for my needs. With the 70 on the back it has enough power to give the kids a good tube ride. It's also roomy and quick enough for a full day of fishing. Not bad for less than $1000.

Rgds

 

[Swivelhart]

Re: Reluctant 70hp but then vroom...

I will send it again... thanks

 

[Swivelhart]

Re: Reluctant 70hp but then vroom...

How do you like the ride of the tri-hull? I was looking for one because I like the open bow but I could not pass up the deal I found on my glastron.

 

[eavega]

Re: Reluctant 70hp but then vroom...

How do you like the ride of the tri-hull?

Very steady at anchor and at slow speeds, but when you are blasting across the lake WOT, it will shake the fillings out of your teeth. It does seem to cut a very tight corner at speed, though. I can very easily turn kids from tube riders to swimmers by throttling up and cutting the helm over

I would probably look for a v-hull bowrider for my next boat (whenever that may be)

-Rgds

 

[Swivelhart]

Re: Reluctant 70hp but then vroom...

I had a few old runabouts in the past before I got my glastron. I had an old Stuery that always seemed to plow through the water when there was a wake...and my old Larson rode real nice but never seemed quick enough. When I got my glastron on plane the other day I was amazed at the difference in ride quality. It was pretty fast and handled the very rough chop on Kentucky Lake in 15mph winds very well. It really smoothed them out. I always liked the idea that the tri-hulls were stable at rest and very roomy though. I am anxious to tear down the carbs...Thanks for your help and I will keep you posted. This was my $200 boat when I first picked it up from an old man. I also gave him an old outboard. Glad I took the chance on it! The only thing I needed to do was replace the steering cable...of course the upcoming carburator work. As I see it when you buy a boat for under $2000 there is going to be some work needed anyway. If you can find one (like you did) for cheap and put a few hundred into it by doing the work yourself it is worth it and rewarding.

 

[Swivelhart]

Re: Reluctant 70hp but then vroom...

One has to love the green algea from sitting under a walnut tree for two years. Fortunately it all just washed off effortlessly.

 

[30yrnavy]

Re: Reluctant 70hp but then vroom...

Check your PMs. Problem developed from manufacturing apparently. Just like when a vehicle manufacturer issues a recall. Johnson corrected it in subsequent model years. My thing was how could a motor from 1976 make it to 2011 without this manufacturer-recommended modification having been performed. It can and has happened, though, since it happened to me. When you read through the mods, you will find that there is a very easy way to tell if your carbs have already been modified, so I was sure that mine were not.

Good luck, and let us know if it works for you.

Rgds

eavega: I just recently bought a 1976 Glastron T-156 with the Johnson 70 HP (1976) motor and am in the middle of replacing the boat's floor. After reading this thread I'm wondering if my motor has had the carb modification. Could you please PM me the bulletin concerning the mod? Thanks.