1980 60HP 2 cylinder Mariner Top Speed Less than 28mph

[kmk89]

I just picked up my first boat the other day with a 1980 60HP 2 Cylinder Mariner on it (motor looks like an alien head). The boat is a fiberglass 15ft TideCraft V-15 rated to a horsepower of 100. Engine has 130 psi compression in each cylinder, good spark on both plugs but the prop is pretty dinged up. Not sure the pitch or diameter of the prop yet. I took it out the other day with 6 gal of gas, 2 batteries, some other misc small stuff and it got up to 28mph with just me on board (170lbs) and only 26mph with me an another guy (170 lbs). Is this about the top speed for this motor and boat combo? What would be the right pitch and diameter prop for this motor?

The boat does not have a tachometer and the motor does not have power tilt/trim, but I can change the tilt angle manually on the trailer using the 4 notches on the motor. Any help is greatly appreciated.

 

[JB]

Re: 1980 60HP 2 cylinder Mariner Top Speed Less than 28mph

You are going to need a tach to evaluate the prop/engine package, kmk. A lot of things could be wrong.

You are underpowered according to our rule of thumb (at least 70% of rated power for satisfactory performance), your boat may be carrying a load of water, your engine may be poorly propped or it may be down on power.

Put a tach on her and see what rpm and mph you get at WOT. Let us know that critical info and we can help you get things right.

My guess is that you are about as fast as you can get with that package, but I wouldn't declare that without the test. There may be room for improvement.

 

[Dave1027]

Re: 1980 60HP 2 cylinder Mariner Top Speed Less than 28mph

(motor looks like an alien head)

Alien head? Pics please.

 

[Faztbullet]

Re: 1980 60HP 2 cylinder Mariner Top Speed Less than 28mph

It the Yammy Mariner/Merc import and the cowling look like the creatures head in movie Alien!!! If it a 1980 model it is the small bore 82mm as the later ones are bigger bore 84mm. Thats about all your going to get with that setup , a tach will help you choose the correct prop and rpm range but you will still be 1-3 mph of what your running now.