1976 Mercury Mariner 75hp

[jcgizmo69]

i have a 75 hp engine, 1976 mariner that only goes about 20 miles an hour at top speed. i took it to a repair shop to have the transom fixed along with a tune up and the guy told me that that was all i would get out of this motor. is this true or is there something i can do, besides replacing the whole thing, to get the boat to go faster? thanks in advance for any feedback!

 

[achris]

Re: 1976 Mercury Mariner 75hp

On a big heavy boat? yes... On a small light boat, no....

What RPM are you making at WOT? What size propeller (pitch, in inches) does the engine have on it?

Chris...........

 

[jcgizmo69]

Re: 1976 Mercury Mariner 75hp

i don't know what model boat i have. i know it is a sea sprite and the tag number is ssb10396m81g. on the prop i can see the name mercury marine trophy. there is an 48-825942a45 25p number that is on he center of the prop. there is another number 802257 that is towards the edge against the boat and a bf towards the edge that is away from the boat. i couldn't find any other numbers. hopefully you will be able to decipher what i have. thanks for your response!

 

[achris]

Re: 1976 Mercury Mariner 75hp

Unless that boat is about 12' long, then that is way too big a propeller. What length is the boat. Remember that I am in Australia and we don't get the same boat models here as you get. Please be descriptive of the boat, not just a name of a manufacturer.

What RPM is the engine making at full throttle?

Chris.....

 

[jcgizmo69]

Re: 1976 Mercury Mariner 75hp

it's a 16 footer fiber glass boat. i dont know about the rpm's because the gauges are not working. other than the numbers i posted, i dont have any other information. thanks in advance!