1985 Larson 140HP Mercrusier

[harmanoff]

My friend and I have been working on his boat that he bought about 2 months ago. Since then we have had issues with the motor not running right all.

1st Issue: Leans to the left until you get the tilt of the moter just right and its level for the most part. How do you fix this?

2nd Issue: My outboard reaches 5500Rpm's and i was told for my engine, it is suppose to reach that for wide open throttle. Well his reaches maybe 4000 if we are lucky.

3rd Issue: It hesitates alot, runs rough. What needs to happen? What is the best products to put in these as far as wires and plugs? We want to get it running right.

4th: What is the recommend RPM's at WOT for this engine? Is it 5500RPM's?

 

[Alumarine]

Re: 1985 Larson 140HP Mercrusier

1. You can try adjusting the trim tab on the bottom of the drive.

2 and 4 if it's a 3.0 litre then WOT is approximately 4200 to 4600

3 do a tune up use marine parts

 

[harmanoff]

Re: 1985 Larson 140HP Mercrusier

Well its a 4 cylinder, not a 6

 

[harmanoff]

Re: 1985 Larson 140HP Mercrusier

Anyone lol come on I have read so many other posts and everyone has good advice but then go to mine and no one seems to reply

 

[vipzach]

Re: 1985 Larson 140HP Mercrusier

Do you know what 4 cylinder it has? The 3.0 is pretty common. If it is a 3.0, then I believe they use AC MR43t's. When was the last mjor tune-up? Plugs, wires, cap/rotor or points, fuel filter change, replace all fluids, check timing, rebuilt the carb..................? The 3.0 is a pretty solid motor, but has to be timed right. If none of that has been done, then that is why you can't get more than 4000 rpm's. Could also be too big of a prop. Any work been done to the outdrive? Does it have a hydrofoil on it?

You have to provide motor specifics for anybody to give you good help. If you do not know, then find the motor and drive serial number.

 

[Don S]

Re: 1985 Larson 140HP Mercrusier

Anyone lol come on I have read so many other posts and everyone has good advice but then go to mine and no one seems to reply

Don't get in a hurry and demand people answer your questions. That's a sure way to get no replies at all.

Who mentioned it was a 6 cyl? A 3.0L engine is the same thing as a 140.

Next, you don't have an outboard back there, it's called an outdrive

Regarding your questions.

1. You need trim tabs
2. As mentioned in the first reply, you should be between 4200 and 4600. The 140 is NOT an outboard, don't expect it to run like one.
3. As previously mentioned, you may just need a tuneup and include a compression test. When was it done last?
And be sure to use marine parts.
4. As stated perviously, 4200 to 4600.

You also need a service manual for your engine if you plan of fixing it propely.