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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.
 
so I’m 16 and I just bought a 1984 Continental Mach 3 cruiser and the prop and everything was taken apart and was wondering if someone knew how we could get that put back together and installed on the boat

It’s not letting me put a picture on here so if you would like to see what I’m talking about, I can get you a photo thanks a lot
 
Hollywood7744, Let me help you help the guys in here to be able to help you.

There should be a metal tag on the back of your engine that has your ENG SERIAL Number. That is the most important thing to post on here because without that information we cannot provide you with accurate information. We cannot see your engine okay?

Also you need to start your own post. Dont be afraid. This thread was started by another and the answers might get all mixed up if your questions start to be answered.

Alot of the people in here are retired factory trained folks who love boats and helping people. You will get information here that you wont get anywhere else.

I recommend getting a service manual either paper copy or online and keep it handy. You also need your ENG SERIAL No. to get the correct manual.

Good Luck with your build.
RK
 
HOLLYWOOD7744 said:
so I’m 16 and I just bought a 1984 Continental Mach 3 cruiser and the prop and everything was taken apart and was wondering if someone knew how we could get that put back together and installed on the boat

It’s not letting me put a picture on here so if you would like to see what I’m talking about, I can get you a photo thanks a lot
Click to expand...
If you take a pic with your phone it will be to large and I believe its in BMP format which is a large data format for images, also its better if it is a JPG fornat for this site.

If you have a laptop. Open image in Paint and shrink size by 50-75% and save as JPG. Then you can upload to your post
 
Photos must be less than one Mb. Many phones have an option called email that will size the pictures down to use less data when sending. Otherwise they’re all kind of free programs that you can do it with personally I use something called Ifranview.
For a video it’s easy to take a fairly long video published it on YouTube and make it public so anyone with the link can see it and then just post the link here
 
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