Rebuilt Mercruiser 140/3.0 doesn’t have enough power to plane

[alldodge]

The motor sounds bad.
I think its either was not rebuilt correctly. Rings not installed correctly, timing, rocker adjustment, I don't know. With a cylinder showing oil, maybe rings

 

[jmpridgen]

Definitely possible. Compression was 150 on all 4 when I checked it a few weeks ago. I do see a fair amount of gas coming through the valve cover vent hose though. I’m not sure what’s normal.

It will be really disappointing if I have to sell a non-working boat

 

[jmpridgen]

The oil level is a little high. I haven’t thought much of it until now. And I’m using a friction modifier to increase the zinc content. Is it possible that the lifters are collapsing because of the oil aeration? I wouldn’t think that would cause such low power though.

 

[alldodge]

I do see a fair amount of gas coming through the valve cover vent hose though. I’m not sure what’s normal.

Gas in a vent hose is not normal. Which hose?

 

[Scott Danforth]

I do see a fair amount of gas coming through the valve cover vent hose though. I’m not sure what’s normal.

it it the clear tube coming from the fuel pump? if so, your fuel pump ruptured. that line is to direct fuel from a bad fuel pump to the motor so it runs bad, then you fix it vs having fuel enter the bilge and blow up

 

[jmpridgen]

Gas in a vent hose is not normal. Which hose?

The line that runs from the top of the valve cover over to the intake. To feed crankcase gasses back into the combustion chamber.

 

[Scott Danforth]

The line that runs from the top of the valve cover over to the intake. To feed crankcase gasses back into the combustion chamber.

there should not be gas in that hose. maybe oil residue, however never gas.

 

[jmpridgen]

It definitely has something coming out . You can see it in the second video in my first post.

 

[jmpridgen]

By gas, I should clarify I don’t mean gasoline. But I mean gas like combustion gas.

 

[alldodge]

The line that runs from the top of the valve cover over to the intake. To feed crankcase gasses back into the combustion chamber.

Blow by on a fresh rebuild, not good.

As before, something or something's were not done correctly

 

[jmpridgen]

Well, I had a boat mechanic take a look and it took a while due to his schedule, but he figured out the problem. 4/8 of the lifters are extremely worn. 2 of them even have holes in the bottom. This is probably my fault due to not lubricating everything properly on startup. I did add a ZDDP additive and did a break-in procedure, but it took me a while to get the engine started. I was also too cheap to buy the drill attachment to prime the engine with oil. So I'm not surprised. I was in a rush and wanted to finish the project. Lesson learned.

At one point I thought the motor sounded like it had a clogged exhaust, and 3/4 exhaust valve lifters are worn through. So I think that theory makes sense. Only cylinder 4 had both lifters operating correctly.

Mechanic is going to take the engine out, inspect the bottom end and we'll go from there.

I attached the worst example.

 

[Scott Danforth]

normally when a lifter wears that much, the cam is worn as well.

glad you found the problem.

BTW, in the future, a screw driver, hack saw, a bit of copper pipe and you can make a priming tool.

 

[MarcelSydney]

normally when a lifter wears that much, the cam is worn as well.

glad you found the problem.

BTW, in the future, a screw driver, hack saw, a bit of copper pipe and you can make a priming tool.

Thats cool. Love to see that trick Scott (or should we call you MacGyver). Got a video?

 

[jmpridgen]

Well, mechanic took it apart. The crankshaft bearing surface is ruined. It would have to be turned down and oversize bearings installed. Also, one of the rings on cylinder 4 scored the wall. So I am back to square one. It could probably be rebuilt again, but at this point I just want a boat that runs.

It’s not a real nice boat. I think the previous owner put plywood over the existing floor and it’s a little soft towards the back. Is it time to just bite the bullet and buy a different boat? I put a lot of work into the boat redoing the wiring, shift cables, bellows, etc. So it’s a tough decision.

If I decide to fix it, what's my best bet for finding a rebuilt or used engine? The head on the engine is still good. Would I be able to purchase a rebuilt short block to save some money? Or does the head on an old engine not fit the newer blocks? Anything I need to worry about fitment wise if I got a newer block mated to my existing outdrive? The serial number for the existing engine is 4779114 and it has an SE106 outdrive. Anyone have any experience with these remanufactured eBay long blocks? https://www.ebay.com/itm/163788036534?hash=item26228719b6:g:eNgAAOSwaplceYpb

 

[alldodge]

Many here have had good luck with Michigan Motorz
https://www.michiganmotorz.com/3-0l-marine-engine-1968-1989

 

[alldodge]

Your motor could be rebuilt most likely, just need a good machine shop

 

[jmpridgen]

Yeah, there’s a good one pretty close to me which did the original work. But that MichiganMotorz engine isn’t too bad. If I rebuild the current one, the mechanic would be the one to do it. So it may be a wash in terms of cost since his labor is pretty expensive. The block may have to be rebored if the scratch is deep enough. I’m not sure how much farther they can go as it was already bored .030” over. I assume I’d have to get new pistons too.

Are there other costs to a rebuilt motor I’m not considering? Like the freight costs?

 

[alldodge]

In most cases there is shipping. With a long block gaskets will be the same. If any block is bored then its new pistons

 

[tank1949]

Well said, will do. I haven't run it very much because I've been too afraid I'll damage something. I'm glad you feel the same.

Dubs283:

Will do

I'll verify the dwell. I think there's a way I can do it with my multimeter measuring frequency or pwm percentage. Otherwise, I'll just get a real dwell meter.

I will verify the exact number, the service manual I have says 6°. I was hoping that verifying it was around that range would be good enough.

I'll do some research for this. Thanks for the tip. Mine has the hard fuel line so I wasn't sure if there was any way to attach something inline.

I did replace the points, I forgot to mention this. It came with the kit.

I mean the diagnostic pickup for an oscilloscope. Like this one on Amazon. I wanted to verify every cylinder was firing. I don't have a way to figure out which spark is which cylinder, but the waveforms looked reasonable at idle.

I will try this. Since that pulley is directly connected to the crankshaft, the timing is as simple as using a protractor, right? 30° from the 0 mark on the timing cover is 30° from top dead center?

The plug wires are hooked up correctly. Going clockwise around the distributor, the plug wires are hooked up 1, 3, 4, 2.

I tried to rotate the distributor while it was around 2500rpm and couldn't get anything to change. So I don't think the timing is too advanced. I'm going to chase the fuel hypothesis first.

Are there any brand preferences on fuel pumps? Are the cheap ones on Amazon really okay? I don't want it to leak into the boat while I'm on the water.

I'll report back my findings. Will be a few weeks before I'm back with the boat on the water.

Advice is much appreciated. I've learned a lot lurking on iboats.

With timing light aimed at timing tab, rev motor and see if distributor advances. I am guess full advance should be 30 degrees. But, you should at least see timing marks showing advancing.

 

[Grub54891]

Wow, If the floor was soft and layerd over, then got soft again, I'd say the boat is on it's last legs. The stringers and transom are next to fail.