mercruiser 165 - chevy 250 inline 6

[83mulligan]

I have to pull my motor to do some stringer and transom work. While its out i figure it would be a good time to go through it and rebuild/replace what needs done. My first question is what is the progression of tests I should do. I think compression is #1 and then possibly leak down. Should I do those and post the numbers here?

Second, can any engine mechanic help me rebuild this or is there anything specific to "marine" mechanic that I should be aware of?

 

[chiefalen]

Re: mercruiser 165 - chevy 250 inline 6

First test compression do it right and then post the numbers. We can go from there.

 

[Zackman]

Re: mercruiser 165 - chevy 250 inline 6

You may find Mercruiser Service Bulletin 97-25 useful, here's a link http://www.boatfix.com/merc/Bullet/97/97_25.pdf​

 

[83mulligan]

Re: mercruiser 165 - chevy 250 inline 6

Rats, that normal room temperature part is going to delay this. When I can get it inside a heated space, I will proceed.

Thanks Zackman, I printed that off.

 

[83mulligan]

Re: mercruiser 165 - chevy 250 inline 6

Second, can any engine mechanic help me rebuild this or is there anything specific to "marine" mechanic that I should be aware of?

Any advice on this? Here is the deal. The mechanic is a friend of a friend. Supposedly a good mechanic that has rebuilt many engines and does great work. Not a marine mechanic though. I may need to commit to something to get the engine pulled and in a warm shop. I just need to know if there is anything "marine" to rebuilding the engine outside of using the proper head gasket.

 

[chiefalen]

Re: mercruiser 165 - chevy 250 inline 6

Nope he rebuilds he can rebuild this also. I did 2 250's in the 70's. 2 novas.

Just need brass plugs and marine gaskets.

 

[83mulligan]

Re: mercruiser 165 - chevy 250 inline 6

can i do the compression test in cold weather and get a general picture of what's going on?

 

[Bondo]

Re: mercruiser 165 - chevy 250 inline 6

Yes...

 

[chiefalen]

Re: mercruiser 165 - chevy 250 inline 6

Listen the weather is 45-50 run a hose to it make sure all the plugs is in, run it 15 - 20 minutes pull the hose off and let it drain with the drive all the way down.

Bye the time you get all the tools ready and pull plug 1 and get a paper and a pen, you can pull the center plug on the dizzy so it don't start and do the compression test. It will have cooled enough.

 

[83mulligan]

Re: mercruiser 165 - chevy 250 inline 6

Ran compression on cold engine.............before chief responded . These numbers are on a winterized engine (fogged) They came back like this:

1: 120
2: 125
3: 125
4: 125
5: 135
6: 137

No water at storage to run it. It's cold, around 32 degrees in the warehouse. Not going to get any warmer this week and I need to get into gutting the transom and stringers, so I just did it. Feedback? I know the spec says 150. Greater than 100 psi acceptable, no less than 30% lower than highest reading.

Not sure how fogging oil for storage and cold weather affects this.

 

[Alumarine]

Re: mercruiser 165 - chevy 250 inline 6

Those numbers are good, considering the engine was cold and had been sitting.
They will only improve after the engine has been run.

Unless you have an issue with the engine, I'd leave it alone.

 

[83mulligan]

Re: mercruiser 165 - chevy 250 inline 6

Those numbers are good, considering the engine was cold and had been sitting.
They will only improve after the engine has been run.

Unless you have an issue with the engine, I'd leave it alone.

I kind of thought it would be opposite because of the fogging oil and denser (colder) air. So, the numbers might be inflated was my guess. I don't know though, that's why I ask all the dumb questions.

 

[chiefalen]

Re: mercruiser 165 - chevy 250 inline 6

Unless there is a issue you not telling us about i would leave it alone also.

 

[83mulligan]

Re: mercruiser 165 - chevy 250 inline 6

the only issue it had last year was after lengthy trolling sessions a couple times it would be bogged down and not want to run. I had to run it around 1800 rpms for a few miles back to the cabin and not on plane. I know trolling for 6 or 8 hours loads it up, but i've never had that problem before. Also, when the impeller in the lower unit failed, it got hot (215 F) before i noticed and shut it down. That was only for a couple minutes at most but it was enough to melt the lower housing of my impeller. Aside from that its been a great engine. I put about a hundred hours a year on her. The hour meter reads 4800 though.

I thought since I had to pull it anyway that this would be a good time to look at all the valve stuff and the seals, especially the head gasket. Also considering electronic ignition because it sits a lot, a long ways from home. So points and condensor gone would be a nice thing for me.

 

[chiefalen]

Re: mercruiser 165 - chevy 250 inline 6

You are right time for a full rebuild if it can be rebuilt? Goes to show you the durability of the inline six.

 

[Fishermark]

Re: mercruiser 165 - chevy 250 inline 6

Also considering electronic ignition because it sits a lot, a long ways from home. So points and condensor gone would be a nice thing for me.

The compression numbers would certainly not be reason to do anything to the engine. As others mention, they will only get better after running up to operating temp.

I would suggest putting a Pertronix kit on your engine for the electronic conversion. I have done a few and have always liked them. Especially for a boat like yours which sits for long periods of time. The points glaze over and need to be replaced. A big deal? Probably not, but with the electronic upgrade you get more consistency and less maintenance hassles. Not any performance gains, just more consistency.

 

[chiefalen]

Re: mercruiser 165 - chevy 250 inline 6

Why she locked up and not run got nothing to do with compression. Could be hydro-locking with water getting in who know till you pull it apart.

The big question is can it be rebuilt? Some are just to far gone, to be rebuilt.

This close to a 35 year old motor? Never gave the year.

 

[Fishermark]

Re: mercruiser 165 - chevy 250 inline 6

it would be bogged down and not want to run.

Why she locked up and not run

To me, that's two different statements. If I am understanding your description correctly, it sounds like the engine would be rough running after a lengthy run at trolling speeds - which could be many things - plugs fouling out, etc.

Or are you saying it would lock up and not run at all after trolling? Two completely different scenarios.

 

[83mulligan]

Re: mercruiser 165 - chevy 250 inline 6

A couple things. First, I forgot to mention, it was rebuilt completely in 1992. I think, but am not positive that it has around 1500 hours on it since the rebuild. I know i bought it in 1996 and have put on about a 1000 hours myself.

The bogged down part. After trolling a couple times last year for about 6 hours or so..........It would not want to get up and run. It would run at about 1800 to 2000 rpms max. The boat wouldnt' get on plane. (WOT is 3800 or 4100 depending on how i have it propped). I rarely run her above 2800. Now, after sitting for a couple hours it would run fine again going back out. I had messed with the idle screws before this started happening. I haven't put the time into tuning the carb like the one post in the sticky's tells how.

My thought is just to open up the top and go through what we can see and verify. Clean it up. Leave the pistons and rings as is. Just look it over and assess further since it will be out of the boat and on the stand and I have a mechanic willing to do the work for 200 to 300 labor.

I'm familiar with leaving well enough alone, but I also want to take advantage of whatever I can when I have the engine out. Also, I bought a Yamaha t-8 this past fall, so there will be very few hours idling along on the engine going forward. Just for running out and in, so hours per year should be greatly reduced going forward.

Oh, and the motor is a 1973

 

[Fishermark]

Re: mercruiser 165 - chevy 250 inline 6

I had messed with the idle screws before this started happening. I haven't put the time into tuning the carb like the one post in the sticky's tells how.

No harm done in removing the head and checking things out. You can even take the valves out and lap them in and put new valve stem seals in if you want. Very little money and just a little bit of time. But the biggest thing you ought to do while you have the time is to give some attention to the carb. Just my humble two pennies.