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1986 sea sprite 185 continental engine/prop questions

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1986seaspite

New member
I just purchased my deceased uncles boat off my cousin and needed some information, its a 1986 sea sprite 185 continental with 120 horse mercruiser, i need a new prop and wasnt wondering if anyone had some suggestions on type and pitch, i was going to see if i could find a used stainless prop but people at work where telling me to go with aluminum, any inputs? What oil should i run in this? , i was wondering if anyone new the differences between 120 horse to the 140 or 170 horse 4 cylinder, is there any common things with this motor that should be addressed? The boat was maintained and just had the outdrive rebuilt, what octane gas should i run through it?
 
Aluminum prop only.

this is not a high power or high speed boat. Aluminum will break/bend most times before the prop shaft or gears.
Stainless steel wont!

Prop size is pretty much determined by the pitch on normal props. Typically most boats are designed to run a 17, 19 or 21 pitch prop. They will all be around 14 inch diameter +/- 1/2 inch

Many factors make up what works so we can not tell you.


The key is...........1/2 tank of gas loaded with normal supplies and you. run the boat at wide open throttle with the out drive trimmed out for max performance and the RPM'S should be at the specified max, typically around 4600 rpms +/- 200.

once you achieve this max rpm then that prop being used is the correct pitch.

Mercruiser high performance gear lube in outdrive and 20-50 weight oil or mercs 20-40 weight in the motor

the difference is size and power

170-120 = 50 hp

140-120 = 20 hp

which equals higher speed and greater torque
so you have the lessor of all of them........

This is a simple putt putt boat for simple enjoyment. Not for slalom skiing and high speed wave jumping.

You may get 35 miles per hour maybe 40 if your lucky.
It will pull a two ski person of light to moderate weight.......a 260lb + person not so much........

As long as the motor timing is set to spec 87-89 octane should be fine.....again this is not a high performance motor of any kind.
 
kghost said:
Aluminum prop only.

this is not a high power or high speed boat. Aluminum will break/bend most times before the prop shaft or gears.
Stainless steel wont!

Prop size is pretty much determined by the pitch on normal props. Typically most boats are designed to run a 17, 19 or 21 pitch prop. They will all be around 14 inch diameter +/- 1/2 inch

Many factors make up what works so we can not tell you.


The key is...........1/2 tank of gas loaded with normal supplies and you. run the boat at wide open throttle with the out drive trimmed out for max performance and the RPM'S should be at the specified max, typically around 4600 rpms +/- 200.

once you achieve this max rpm then that prop being used is the correct pitch.

Mercruiser high performance gear lube in outdrive and 20-50 weight oil or mercs 20-40 weight in the motor

the difference is size and power

170-120 = 50 hp

140-120 = 20 hp

which equals higher speed and greater torque
so you have the lessor of all of them........

This is a simple putt putt boat for simple enjoyment. Not for slalom skiing and high speed wave jumping.

You may get 35 miles per hour maybe 40 if your lucky.
It will pull a two ski person of light to moderate weight.......a 260lb + person not so much........

As long as the motor timing is set to spec 87-89 octane should be fine.....again this is not a high performance motor of any kind.
Click to expand...
Ok, thanks for the input! What i meant on the hp difference is what makes the difference, different head, compression , cam?
 
1986seaspite said:
Ok, thanks for the input! What i meant on the hp difference is what makes the difference, different head, compression , cam?
Click to expand...

Ayuh,.... The 120 hp is a 2.5l Chevy motor,....

The 140 hp is a 3.0l Chevy motor,....

The 170 hp is a 3.7l POS motor that Mercruiser built for themselves,...

So,.... No, there ain't no hot-roddin' yer motor,.... it is what it is, 'n will never be any more powerful,...
 
bondo said:
Ayuh,.... The 120 hp is a 2.5l Chevy motor,....

The 140 hp is a 3.0l Chevy motor,....

The 170 hp is a 3.7l POS motor that Mercruiser built for themselves,...

So,.... No, there ain't no hot-roddin' yer motor,.... it is what it is, 'n will never be any more powerful,...
Click to expand...

Kk ,sounds good! Just checking my options, well at least gas mileage should be good lol
 
And once you get the correct prop on it, don't run it continuously at anything more than 80% of the maximum RPMs... 75% would be better. Boat engine life for stock engines when run at max RPMs is measured in the tens of hours.
 
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