What to check when buying a used mercruiser 3.0

[fishrdan]

Re: What to check when buying a used mercruiser 3.0

Where do the purple, gray and black wires for the ignition go? The wire (black one?, along side the 2 white wires) is for the shift interrupt, if it's connected to 12V it will kill spark. (I think this is the least of your problems though...)

What size are the 2 flywheels. 14" for the 91 and 12.5" for the 81? If so, the triangle coupler won't bolt up as it's too big in diameter. I think you'll find the 14" flywheel won't fit the 81 engine, different bolt pattern, try it though. Then you will have to worry about the starter fitting. Look at the starter on the 81, since there was an automotive fuel pump, hacked choke and new sticker on the starter, I'd be suspicious if the starter was a marine starter,,, spark suppression protected.

I'm not sure how the throttle linkage for the 81 worked, but on my 73 the shift cable/linkage is bolted to the side of the manifold, with another linkage pointing up to the carb, more complex than the 91 carb cable setup. I'd try to figure something out for the 91 cable setup as the 81 setup (if like 73) will require a longer cable and obsolete linkage you'll have to scavenge off another boat or Ebay.

The only way I see this working is:

1- you can get the flywheel/coupler/starter/engine mount problem solved
2- take the 91 head (and everything else on top) and bolt it to the 81 block This will solve a bunch of your issues, for a $40 head gasket. Though,,, that's if the 91 head and manifold are in good condition, not cracked...

 

[mattyrich]

Re: What to check when buying a used mercruiser 3.0

Ok, Fishrdan, Looks like i should have payed a bit more attention to your ENTIRE list.... I have gotten everyting worked out on that list except the throtle cable and exhaust elbow.... but i guess one will take care of the other... When i am trying to swap or purchase a newer style exhaust manifold and install it what do i look at to determine which gasket to purchase and use? do i look at the manifold side or the head side, or both? let me know what you think, Please. Also Do you know where i could find a manifold at a reasonable price? thanks, matt

 

[fishrdan]

Re: What to check when buying a used mercruiser 3.0

That's why I was saying to use your 91 head and everything attached to it, solves a lot of problems; riser, exhaust, carb, linkages... Even if you have to run the 91 head down to a machine shop for a valve job, it's still cheaper than a replacement manifold/riser.

The gasket pic I posted shows the configurations that you could find, and none of them are compatible, try to mix/match and you will have performance issues. A new manifold/riser will probably run you $250-300 and that's a cheap Chinese aftermarket. I bought a Barr for my 140 before the Chinese ones were available and it was $300+ for the manifold and riser, years ago.

The manifold and riser gaskets will depend on what you have, you have to match it up. I have a bunch of extra gaskets and gasket material so it's not a biggie for me. Best bet would be to haul your stuff down to the marine parts place and let them sell you the correct gasket. I've made my own gaskets a bunch of times, the toughest part was finding the correct type of gasket material to make the gasket out of, thick, thin, hard, soft, cork, paper.....

 

[mattyrich]

Re: What to check when buying a used mercruiser 3.0

Ok, so i was able to get the manifold off of the 1991 to swap to the 1981 that im going to try to use? I'm not sure I understand quite yet. Are you saying that the heads are different on these two motors? it looks like they will match up but im not sure? I havent taken the manifold off of the 1981 yet. It looks like the the manifold gasket would match up with a manifold i have that came off of the 1981 (an extra one that came with the motor). does that mean I wont have to change the head as well? Damn these exhaust parts are expensive!!! mine have some rust in them and dont look all that great. Im gonna get some rust dis-solver and soak them for a bit. What do you think i should do. what a pain. I have another question too. I was trying to get this thing to turn over today and sprayed some gas in the carb and cranked it, but all I get is a backfire and some smoke out of the top of the carb and some from the exhaust? Someone mentioned that The distributor may be in wrong. I did it with a buddy and put the 1st cylinder to tdc and put the distributor (EST) in with the rotor pointing toward the first cylinder. Could I possibly be on the first cylinder on the wrong stroke, and if so, could i just pull the distributor out and turn the rotor/shaft 180 degrees and put it back in? Im getting spark on all four cylinder though. Will it spark if the distributor is synced on the wrong cycle?

 

[fishrdan]

Re: What to check when buying a used mercruiser 3.0

Ok, so i was able to get the manifold off of the 1991 to swap to the 1981 that im going to try to use? I'm not sure I understand quite yet. Are you saying that the heads are different on these two motors? it looks like they will match up but im not sure? I havent taken the manifold off of the 1981 yet. It looks like the the manifold gasket would match up with a manifold i have that came off of the 1981 (an extra one that came with the motor).

Don't know, you have to take the manifold off and see what the ports look like, could be the same, could be different.

does that mean I wont have to change the head as well?

Check the port configuration. If the port configuration is different, well then,,, yeah you will need to swap the head if keeping the 91 manifold/riser. Don't think "eh it's close enough" or you will hurt performance, the ports need to match up.

mine have some rust in them and dont look all that great.

Rust is normal since it's not protected with antifreeze, only thing you have to worry about is the manifold rusting through and causing a leak, but if you are in freshwater it's not as much of a concern as if it's been in saltwater. If you want to clean the rust up, soak the manifold in acid, iron only, not aluminum.

I was trying to get this thing to turn over today and sprayed some gas in the carb and cranked it, but all I get is a backfire and some smoke out of the top of the carb and some from the exhaust? Someone mentioned that The distributor may be in wrong. I did it with a buddy and put the 1st cylinder to tdc and put the distributor (EST) in with the rotor pointing toward the first cylinder. Could I possibly be on the first cylinder on the wrong stroke, and if so, could i just pull the distributor out and turn the rotor/shaft 180 degrees and put it back in?

Timing is off and yes, you could be out 180*. Turn the engine over until you feel compression building on #1, line up the timing marks and re-stab the distributor. You will still need to time the distributor and the EST takes a SPECIAL timing procedure, jumper white wires, jumper shift interrupt wires, blah, blah... Check out the boatfix link posted in one of your other threads, the directions for timing the EST is there, just have to do some digging...

 

[mattyrich]

Re: What to check when buying a used mercruiser 3.0

How do you guys think this elbow and manifold look. Im really not sure, but i cannot afford new ones right now. Anyone wanna trade a good 3.0 manifold set up for valve cover throttle connection and Merc-carb? I have a freshwater cooling system that seems to be in good condition if ya wanna swap? I am a bit worried about the mating surfaces of the exhaust elbow. What do you guys think? Thnks,Matt.

 

[LilRedNeckGirl]

Re: What to check when buying a used mercruiser 3.0

WEll, My sympathies to this guy. What a nightmare. I guess for the rest of us 3.0 folks the lesson is clear, HIRE SOMEONE QUALIFIED TO REPLACE THE ENGINE !!!!

 

[Silvertip]

Re: What to check when buying a used mercruiser 3.0

The answers to most of your questions are in the service manual for your outdrive.

 

[fat fanny]

Re: What to check when buying a used mercruiser 3.0

No! just need to follow the process of elimination with the parts on hand it sound like he has all he needs but may need to do more swappikng than he wants the compatability may also be off by one or two pcs, from either years though. My 1st step woud have definatly been swappin the head from the 91 to the 81 that way it eliminates the port compatability and any linkage alignment issues also this ensures the risers match as well. But my biggest concerns would be with the EST ignition and wiring harness compatability he may find himself in need of the merc service manuals for both years for accurate wiring harness configurations and using a cross between the two to get this monster to fire correctly. He will have to keep hi nose in the manuals and keep a good eye on the wiring schematics.

 

[proshadetree]

Re: What to check when buying a used mercruiser 3.0

Kind of an old thread I wonder if he gave up

 

[LilRedNeckGirl]

Re: What to check when buying a used mercruiser 3.0

the thread just really hit home w/me, as my boat has 2 of these 1985 3.0 engines. beings they are coming up on 25 years old, i have to wonder what is the final season for them, and when it is repower time, what my options will be. i know i would like3 to have a wee bit more power, but on the other hand, the fuel economy of these engines is great. , oh well, hopefully, they last another 25 years....

 

[proshadetree]

Re: What to check when buying a used mercruiser 3.0

GM 3.0 engines were used in forklifts, generators and all kids of equipment. Lots of places to find replacement engines. If it were a 470 Merc I would feel a lot worse for for him. They were only boat motors.

 

[mattyrich]

Re: What to check when buying a used mercruiser 3.0

Hey there Iboats family...
So It's been a while since i have been on here. been doing alot of work on the boat. Got the outdrive painted and mated back up. shifts good, and pumps water well...had to make a bracket for the throttle linkage because the manifold configuration was different. it seems to work fine. the only thing i have left is to get this thing dialed in. Im having carb issues, and i have yet to set the timing on the est ignition... I need a light. will any timing light work?

The carb; I dont know if this was the original carb to this motor, but i dont think it was. when i bought the motor. the lady threw in a bunch of extra parts, that the previous owner apparently swapped out. there was a manifold. there, but it has a different bolt pattern and mating surface shape... I am worried that the carb base hangs over the sides ( bow and stern) of the mating surface of the manifold. there is a little bell shape curve protruding out of the middle of both sides the carb base plate mating surface... the manifold mating surface is pretty much rectangular and doesnt curve out in the middle of the two sides. therefore, the carb baseplate hangs over the manifold mating surface in the two small areas on either side.this doesnt seem correct? Ill have to take some detailed picks.

Does anyone familiar with the manifold bolt patterns/ mating surfaces and the carbs that are compatible with them? I am afraid i may need a different carb or maybe just a different base plate? the bolt pattern is for a rochester 2 jet carb... says Gm on it too? heres some pics of progress and carb...

I cant seem to get the thing to idle. It will start, but i have to hold the choke open to get it to start. then when its running it will stall out if i dont have the choke open enough, but it will idle high when i hold it open. seems like i cant get the choke adjusted right, either way...

 

[mattyrich]

Re: What to check when buying a used mercruiser 3.0

here's some pictures of the carb if anyone can help identify it. it looks like it was painted black at one point if i look close... anyone know whick base gasket i need for this carb. the only numbers i could find on the carb were 61714735 on top of the float bowl in small numbers? says rochester 2 jet and has a Gm in raised letters... I put the electric choke on from the 1991 3.0 motor. seems to be operating correctly. opens up when it warms... Can i get away with just getting base gasket for a rochester carb? i am going to put a new carb kit in it, as soon as i find out if this carb will work on this manifold? Like i said, it was there when i bought the motor? thanks

 

[mattyrich]

Re: What to check when buying a used mercruiser 3.0

Well, if anyone is still following along...
I failed to mention that i finally decided to go with the manifold that was on the 1981 motor and make a bracket for the throttle cable to mate up on the carb linkage. worked pretty good.
I got the carb cleaned up and finally got it to idle with some adjustment of the linkage, idle stop screw, and the mixture screws. sounded good, so i decided to take her out for the maiden voyage and see what problems i ran into. Go with another boat if you do this... lol
To my delight, the motor ran well, had great power and really had no mechanical problems, or so i thought.

After running at an idle for a few minutes, keeping an eye on the motor and guages, i decided to bring her up on a plane. She did well again, so I gave her some more gas and ran her for a few minutes at around 3500-4200 rpm's to see how she liked it. She did great and didnt notice any problems, so we decided to take her up the river a few miles and hang around. After sitting on the shore with friends for a while, I noticed that there was some oil in the bilge! guess it was a mixture of water and oil, as it was raining off and on.

I decided, at that point, it might be a good idea to head back as i didnt know where the oil was coming from and it was around 4 o'clock. didnt want to be getting towed back after dark...

While running back kept the engine compartment open again and watched closely to see if i could find where it was coming from. It looked as if there was some oil coming down from around the bell housing... What could that be i was wondering. I assume it could be a plug, rear main seal, oil pan gastket, etc, but im no pro so im not really sure what the other possible culprits may be. Any ideas guys????

I also noticed that there was some oil being spit out from the top of the valve cover at the hole that hose connects to the flame arrestor. Why might this be happening. Could there be too much oil in the engine, and if so would that be happening? I monitored the dipstick on the motor and it didnt seem to change at all throughout the day even though oil still seemed to be accumulating in the bilge? enough to notice that it was increasing. However it is also probably some water accumulating as well as it was raining and the boat had gotten pretty wet...

I check the gear oil to be sure, and the fluid is still full with no signs of drop or water intrusion...

I guess my questions are thus...
1982 mercruiser 140 hp SN# 6018808 ( I think) no engine tag...
1991 alpha one Gen II drive. ( I had to change some things to get them to match up)
1991 Bayliner capri 17'

The level on the dipstick is at or above the FULL mark...
Oil looks good and no water... dipstick level is staying the same...
The oil in the bilge area is darker brown to black. However the new engine oil is still more of a blonde color as i just added oil to the motor. it was low when i got it, and i added oil to bring up the level. I think i may have added too much? it takes 4 quarts but i added at least three, waiting for it to raise up before each. I figured i could just drain some oil if the level got too high... I know, i should have just done an oil change, but i dont have a pump, and the oil drain hose connected to the bottom of the oil pan wont fit out of the 1991 bayliner drain plug hole. go figure.

Anyways, I was wondering if anyone could explain to me the the possible effects of too much oil in the engine?

Also, what are the places that the oil could be leaking from and how should i check and/or pinpoint the leak if there is one?

Furthermore, why would oil be being spit out of the hole on top of the valve cover?

Keep in mind that the motor seemed to run great for a few hours without any performance issues...

I only have one more question/concern. The motor seemed to run cool all day as i could hold my hand on the manifold for ten seconds after running at 4000 rpm's for at least five minutes straight. However, the manifold gets very hot just below the carb where it mates up to the head. Should i be concerned about this and what could cause it? running lean?

Thanks to anyone who has the patience to stick it out and read this... I ramble on but I think it is all pertinent info. Thanks for any help. I am so happy to have this thing on the water but dont want to cause any damage to her. Thanks, again, matt

 

[JWebber]

Re: What to check when buying a used mercruiser 3.0

Too much oil can lead to frothing and pressures, so thats a good reason why you have oil spitting out the breather hose. What temp are you running at? and have you replaced your impeller in the outdrive? It pumps the raw water up to engine then your engine cirulation pump pumps the water thru out the blaock and out to riser etc..

 

[mattyrich]

Re: What to check when buying a used mercruiser 3.0

thanks for taking the time to read my thread. I have replaced the raw water impeller in the drive and it is working well. Im not sure of the exact temp because my guage isnt working, but i have been keeping a close eye on her. the gauge pegs out to position B (per manual terminology) when the tan wire is grounded, so I believe that i must need a new sender. I will ring out the wires and test my sender before buying a new one. I can hold my hand on the manifold for ten seconds after running at 4000 plus rpm's for 5-10 minutes, so i think the temp is goodl... the only temp thing im worried about is the spot on top of the manifold directly between the carb and the head. it seems to get extremely hot in that one area? What could cause and fix this or is it normal. thanks again, Matt

 

[mattyrich]

Re: What to check when buying a used mercruiser 3.0

Here's a picture of her maiden voyage. Posting a few questions about gauges, etc... in the mercruiser forum if anyone wants to follow. thanks!

 

[mattyrich]

Re: What to check when buying a used mercruiser 3.0

WEll, My sympathies to this guy. What a nightmare. I guess for the rest of us 3.0 folks the lesson is clear, HIRE SOMEONE QUALIFIED TO REPLACE THE ENGINE !!!!

Hey thanks for your sympathies, but i got her in the water and runs GREAT! Now I'm just trying to track down a possible oil leak, but other than that I have fixed all of the problems myself so I guess that means Im qualified. Just saying, we all have to start somewhere. Watch out for mis-information before starting a project...

 

[mattyrich]

Re: What to check when buying a used mercruiser 3.0

No! just need to follow the process of elimination with the parts on hand it sound like he has all he needs but may need to do more swappikng than he wants the compatability may also be off by one or two pcs, from either years though. My 1st step woud have definatly been swappin the head from the 91 to the 81 that way it eliminates the port compatability and any linkage alignment issues also this ensures the risers match as well. But my biggest concerns would be with the EST ignition and wiring harness compatability he may find himself in need of the merc service manuals for both years for accurate wiring harness configurations and using a cross between the two to get this monster to fire correctly. He will have to keep hi nose in the manuals and keep a good eye on the wiring schematics.

Thanks for your advice FF and thats exactly what I have been doing. Lots of reading and comparing diagrams... lol Learning alot. I have gotten the boat going pretty well. She did well on her first voyage. Good luck to you!