new guy needing some help

[joelyons50023]

just got this boat from my stepfather it is a 75 glasstron 15ft with a 70hp johnson motor on it. couple of questions when he had it he said that when you would first take off the rear would dive a lot and not go hardly at all until you had some one go to the front and even it out, he said that there was someing to help with that but me being pretty new to this i don't know what that is and also he was not for sure what the oil/fuel ratio was for the engine. any help would be greatly appreciated.

 

[Boss Hawg]

Re: new guy needing some help

just got this boat from my stepfather it is a 75 glasstron 15ft with a 70hp johnson motor on it. couple of questions when he had it he said that when you would first take off the rear would dive a lot and not go hardly at all until you had some one go to the front and even it out, he said that there was someing to help with that but me being pretty new to this i don't know what that is and also he was not for sure what the oil/fuel ratio was for the engine. any help would be greatly appreciated.

First - sounds like a trim &/or weight distrabution issue- do you have power T&T?
Second - mix is 50:1

 

[ezeke]

Re: new guy needing some help

Welcome.

See if you can find a 1" X 3" plate on the side of the port transom bracket that will have a model number for your motor. Failing that, look on the engine block for an aluminum, nickel-sized welch plug that would also have numbers on it.

Once we know the age of the motor, the answers will be more accurate.

 

[joelyons50023]

Re: new guy needing some help

it is a 1975 johnson 70hp 2-stroke motor. does this help?

 

[ezeke]

Re: new guy needing some help

Yes, 50:1 87 or 89 US octane gas to TC-W3 Oil.

Power Tilt and Trim was optional and indicated by the model number, so you will have to tell us if you lift/tilt/trim the motor by hand or hydraulically.

 

[joelyons50023]

Re: new guy needing some help

it is by hand with a pin with different holes to choose from. it is on the 2nd to closest to the bottom

 

[Randybeall]

Re: new guy needing some help

You have preset trim. That is what I deal with on my Fabuglas with Evinrude 70 as well. Experiment with positions which give you reasonable take off and good stability when running. I got the biggest boost when I raised the engine mounting two holes. As captain of your craft it is up to you to determine where loading takes place . That said make one or more people sit in positions to get you the safe take off and cruising. Some people plan where the batteries are located and the live well so that the weight helps the boat to preform. That preplanning can make locating passengers of less importance. Happy boating.

 

[joelyons50023]

Re: new guy needing some help

Would one of those hydrofoils help that are on this site?

 

[itsaboattime]

Re: new guy needing some help

First off, Welcome to iboats!!!


You have a manual tilt and trim.

Your boat is doing what is known as porpoising. Just above the prop is a flat horizontal "plate" that runs around the lower unit that is called the cavitation plate. This should be flush with the bottom of the boat. If its not you may be able to adjust the height of the motor where it mounts to the transom to get it flush.

You may want to set the pin on the lowest hole and see how it runs. Some weight in the bow may help too. My Four Winns has this problem a lil too. I have my trolling motor battery up there under the seats. Generally there is a kid up there too.

Those trim tabs may help you too. Be aware, they are expensive.

If all else fails there are hyrofoils that you attach to the cavitation plate. Alot of guys on this site hate them, but, I say if you've tried everything else and still she porpoises, give them a shot.

These are all just general fixes. To get specific, we will need the model of your particular outboard.

 

[joelyons50023]

Re: new guy needing some help

70esl 75e is what it said on the plate sorry for my ignorance but i work on harleys for a living and this is all new to me

 

[ezeke]

Re: new guy needing some help

Initially, set the thrust rod so that the anti-ventilation plate (the horizontal plate above propeller) is parallel with and in line with the planing surface on the bottom of the boat. The A/V plate should be parallel to the water at cruising speed.

Raising the motor so that the A/V plate is slightly higher than the boat may improve performance, but the higher it is raised, the more unstable the platform is so you have to experiment.

The aftermarket fins that bolt to the A/V plate create a lot of drag, especially in turns.