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Help with 1976 OMC Stern Drive

S

slateroc24

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"My Brother gave me a 1976 Sea

"My Brother gave me a 1976 Sea Ray with a 2.5 Liter 140 HP motor in it. I got it running this week and it runs quite well to my surprise. I took it out today for the first time and I got 3300 RPM and 34 MPH at full throttle. Does that seem right? The motor ran well but seemed Doggy...But it is a 32 Year old 4 cylinder. I set the timing on the motor at 4 deg bofore TDC and checked it at full speed and it was around 4o Deg. How can I find out what prop is susposed to be on the boat. What would happen if someone put to big of a prop on a boat would it make it Doggy? Another big problem is the large rubber seal were the stern drive comes out of the boat from the motor is leaking very bad. Its all dry rotted, and leaks water. How hard are them to change, and what are they called. Thanks in advance for any help. As you can tell Im quite new at this. The great thing is my 3 year old love the boat, and drives everyone nuts blowing the horn."
 
"First of all, if a 2.5L it is

"First of all, if a 2.5L it is a 120 HP engine and not a 140, and You lack about 1000rpm!
Start by doing a comp test, and if possible post a pick of the spark plugs
Then have the seal changed before You take Your 3 year old out again, unless You want to swim back to shore with him. It may be changed without removing the drive, with help of a lot of soap water, I prefer to remove the drive."
 
"Morten, I uploaded a couple

"Morten, I uploaded a couple pics. I didn't pull a plug because they weren't new when I went out. So we would get a false reading for rich or lean. The next time I go out I will put new plugs in and post. Its raining cats and dogs here in New York so I can't do a compression test today but I have a tester and will hopefully tomorrow. I looked up a transom seal on this web site and it gives me a seal to replace OM 313080....Mines a 313081 but it looks from the picture on here just like mine. Replaces OEM #0313080. TRANSOM SEAL Replaces: 313080 (1967-77) 120 HP and UP. Thats me do you think its right, cuz I wanna order it? I for the life of me can not find the Serial# and Model# off my engine. I've been over it with a fine tooth comb do you know were it should be? Last question how do I go about finding out if I have the right prop or ordering the right prop for the boat? My Model # off my drive is 982565 and the serial is 266218. There weren't any kids on the boat her first time out. Just me a friend and some tools. He's in it with me when I'm working on it. Thanks for your help. Okay the pics are too big I will figure out how to resize and send later...."
 
"There is so much info on this

"There is so much info on this site its amazing. I've been reading post since i found this site...what a wonderful sorce of info. But on the flip side it generates more questions. Morten your the only person I've spoke with but for the amount of post you have and reading your posts on other trends you really seem to know your...Stuff. Some of the questions I have now are...Do you think it would be worth switching over to electronic ignition and removing the points, condensor, and balast resistor all together? I don't own a dwell meter, I set the points to .019 the day I ran the boat, set the timing to 4 deg at idle....is that right at idle. I'm so used to setting total advance with the RPM's up that at idle seems weird. I wanna know what drive I have. My Valve cover says OMC 140, so my previos post that I have a 2.5 is just my stupidity. I guess I should ask what is a 140 horse. A 3.0, 3.1?? I know its a 4 cylinder for sure. I've been working on this boat for alittle over a week now. When I got it the motor layed in the back of the boat with broken bolts in the block were the starter once was, now its all I think about, I wanna know all I can."
 
"Sorry for being a bit 'la

"Sorry for being a bit 'late' but I'm in quite a different time zone than You, Malaysia, and I have just started getting my sailing!!! boat back in shape again. Been lying for almost 2 years and not used it.
Before starting to order things and putting in to much money, get a complete budget to make it safe and working. Don't forget the cooling system. I would recommend to pull at least the upper unit and replace the impeller in the water pump. Pertronix ignition system seems to work and reduces a bit of service need. On the other hand the ignition system on the GM 2,5/3.0 engines seems to be quite long lasting. Having a boat You will soon need a multimeter anyway to sort out all electric problems as they occur. By a meter with dwell included, or a timing light with both dwell and rpm reading. Proper tools is half the way to success.
There is only one 'type' on props that fits Your drive, it is just to find the right pitch.One inch pitch change gives about 200rpm change, and for You that would mean 5" down! I think there are something else going on. But first be sure the power is in the engine."
 
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