1975 75hp, question about top speed

[everhart57]

got it to the lake, put in gear and synced the carbs, thought it was running great but speed tops out at 25mph. Is this normal? it's a 1975 75hp chrysler, 16ft 1959 glaspar, with myself (140lbs) and a buddy of mine (about 225lbs). I also have added a steel cap to the transom made of 12 gauge steel. I think that's all. Only have two seats the battery and one 6 gal gas can in there. Also, I burned through that entire can of gas in about an hour? is that right? could that be from adjusting the carbs? Any insight would be helpful. Otherwise it's running great though

 

[jerryjerry05]

Re: 1975 75hp, question about top speed

Normal??? Who knows what normal is.It all varies for the motor.
First check the compression then spark.Check the motor see if it's running right.Start it and pull off one plug wire at a time. If it makes a difference then it's working ok.
Next what RPM's are you getting at WOT. Should be about 5500rpm.
If the motor can't reach the suggested rpm then the prop is probably wrong for the motor.
My brother swapped a motor off a pontoon and could understand the difference what pitches on a prop do.
If the wron prop is on it will affect the fuel economy.J

 

[Frank Acampora]

Re: 1975 75hp, question about top speed

Normal? The only two normal people on this forum are me and you Jerry,----And I aint so sure about you--LOL!

What Jerry said, Everhart--It all varies depending upon hull and engine combo. AND-- if I remember correctly, that year Glaspar would be a round- bottom. They tend to be a little slower than flat bottom or deep vees. Heavy hull too. Bottom line, make sure the engine is running correctly, is propped correctly, and take what you can get.

That said, I would expect that with a little fine tuning of engine position on the transom, tilt pin (if it does not have power tilt), and prop, you should be able to squeek out a little more speed. Don't expect to get an ocean racer though.

Fuel consumption? You are somewhere in the normal range for full throttle operation. Again, it varies, but outboards are notoriously thirsty.