1973 Mercruiser 165 compression

[EdwardC]

What I have:

1973 Sea Ray SRV 193
gm 4.1L with the original Mercruiser I/O

What I know:
compression test:
cyl. 1 105
cyl. 2 120
cyl. 3 165
cyl. 4 140
cyl. 5 30 (not a typo!):facepalm:
cyl. 6 30 (again, not a typo!):facepalm:

YIKES!!

The previous owner removed the head to have the rusted in spark plugs removed by a machine shop. He re-installed the head and then lost interest in the boat. I do not know how competent he was. He did replace the head gasket, head bolts, and valve cover gasket.

This is a 40 year old boat. It has maybe 5 - 10 left in it with TLC.

My Questions:

1. Do I roll it off the trailer and plant tomatoes in it? :applause:

2. Do I buy a different boat and sell this one?

3. Do I try to fix this motor?:frusty:

 

[alldodge]

Re: 1973 Mercruiser 165 compression

Well a boat is always Bring On another Thousand. It all comes down to, how deep are your pockets and do you really like to spend more time working on it then playing on it. For me number 2 is out. I like number 1 but do your your neighbors really like you.... I would go with number 2 but be honest, or make sure to not sell it to someone you know or someone who will look to take revenge.

 

[Don S]

Re: 1973 Mercruiser 165 compression

Since he had the head off, it may be as simple as improper valve adjustment, and it scared him and probably why he lost interest.

I would check that before I did anything else. Check that first, then if that is the problem, you still have to wonder how the rest of the repair was done.

 

[RogersJetboat454]

Re: 1973 Mercruiser 165 compression

Next step is a leak-down test to see where your compression is going.

I bet 5 and 6 may be swapping spit...

 

[EdwardC]

Re: 1973 Mercruiser 165 compression

The previous owner said he only had the plugs removed. the shop did not touch the valve or anything else. If it was me I would have had a complete valve job since it was off the motor, but that is just me.

How do I figure out if the cylinders are "swapping spit"?

My neighbors do not like me. (I think). I am the new guy on the block, and I have noisy kids. And I am not the previous owner of the house who was here since it was built! I rent so if they make me angry enough I will just leave!

I bet I could grow a lot of worms in this boat and set up my own bait stand at the boat ramp!! Teach the kids about business!!

Seriously, I went with option 2 above. I got a new boat that had just come from the mechanic from it's de-winterization with a clean bill of health. If the weather is OK we are going boating this weekend!!

In the mean time I have the Sea Ray for sale on craigslist. I am not very hopeful. If I can figure out what is wrong with it I may have less trouble getting rid of it.

Enough rambling, and thanks for your help. Again, how do I check the "spit swapping" situation? Pull the head, or some simpler test?

 

[998cc]

Re: 1973 Mercruiser 165 compression

Swapping spit? My second motor had low to no compression on 5 and 6 due to the previous owner leaving the engine out in the weather without the exhaust riser installed. This allowed rainwater to collect in the head and rust the valve seats in these two cylinders.

I am at number 3 with my quest to save a 1972 18' Gulfstream with a Mercruiser 165 inline 6 in it. There is now a second engine and outdrive in my garage for parts. If all the new parts come in this week, the plan is to put it back together this weekend.

Would I do it again? It has been a fun as well as a frustrating project, and I have learned alot about Mercruisers in the process. The biggest "plus" is having intimate knowledge of the condition of the bellows, gaskets, seals, U-joints, etc.; I can only imagine their failure could cause some real trouble while out on the water.

If I knew what I was in for back in March, I would have passed on this boat and bought one in running condition. Knowing what I know today, a running boat may give a false impression of being a sound watercraft when it may actually be potentially dangerous. I would do as you did and go with number 2 and certification by a competent mechanic or go with number 3 to be certain of the overall condition. The tomatoes can wait!!

 

[EdwardC]

Re: 1973 Mercruiser 165 compression

Oh that evil rust! Thanks 998cc!! You saved me some frustration! The previous owner did leave the exhaust riser unbolted after he reinstalled the head. I am sure some water got in there. Oh well, lesson learned. I think I am going to part out the entire boat and sell the bits on ebay. I just have to figure out what to do with the hull when I am done.

 

[RogersJetboat454]

Re: 1973 Mercruiser 165 compression

"swapping spit"= neighboring cylinders that are leaking compression into one another, due to a sealing issue between the holes, or crack in the head/block.
A leak down test would be able to show this, and if it's not the issue, it should be able to show what the problem is.

He may not have done a valve job to this, but did he remove the rocker arms when he pulled the head? If he did, there is a chance he improperly lashed the valves (holding them partially open) when he re-installed the rockers.

 

[bubbahemi]

Re: 1973 Mercruiser 165 compression

the head gasket could be bad or like on my boat the water impeller didn't have the key and got hot and a carb screw fell in and messed up the valve