Mercruiser 4.3LX questions

[DeepBlue2010]

Hi All,
I have a Mercruiser 4.3LX. The boat itself (1994 Bayliner 2252) is undergoing a major overhaul as we speak. I started thinking about the engine as well while I am at it. The engine was replaced in 2000 with a short block that was built in the same year (2000). Before I purchased the boat, I took the engine for inspection and the compression test came back with 145 to 150 in all 6 cylinders. The manual says, it should be around 175 in each cylinder. Is it time to think about a rebuild during the winter? How many horse power I am loosing with this drop in compression anyway?
My second question is about parts. I looked up some parts from http://dougrussell.com/. The price differences between this site and a site like Summit is huge. I know that Summit parts are intended for street applications not marine. Based on your experience guys, are there any real difference between the parts? For example, the 12 lifters are going close to $800 on Dougrussel while the whole set PLUS the camshaft are going $300 on Summit! If they are really different in quality, I don?t mind paying the price. I just don?t want to be charged extra premium just because I am a boat owner.


Thanks all

 

[NHGuy]

Re: Mercruiser 4.3LX questions

You can get lifters and a cam anywhere, just get a marine grind. High perf car cams have too much overlap which brings reversion. Reversion ruins motors.
When you find a cam you want post it up here, there are lots of very experienced folks who will be able to help you make a good pick.

 

[achris]

Re: Mercruiser 4.3LX questions

And make sure the lifters are 'anti-pump up'.... At higher revs 'normal' lifters can't move the oil out fast enough and they start to hold the valves open...

Chris.....

 

[DeepBlue2010]

Re: Mercruiser 4.3LX questions

Thanks guys for your fast reply. I used the lifters only as an example of the price variance. The question I am really interested in is ?In general, are these parts really different from their street application counterpart??
I hope someone will be interested in the first question, the compression related question.

 

[Mohawkmtrs]

Re: Mercruiser 4.3LX questions

Different compression guages will give different readings.

Depending on the last time a compression test was done, it may not be a bad idea to perform another one.

However, the real question is: Why is the compression different and where is it leaking?"

A leak-down test will determine where (if any) compression is leaking.

That should help you determine what work (if any) work might be required over the winter.

 

[Fishermark]

Re: Mercruiser 4.3LX questions

How did you do the compression test? Had the engine been run in awhile? Was it warmed up? Lot of factors can affect the compression test. The fact that the cylinders were all close to the same is a good thing. Before you go about buying parts for a rebuild, make sure you do the compression test right first.

 

[DeepBlue2010]

Re: Mercruiser 4.3LX questions

I had the compression test done during inspection before I bought the boat. This was in Aug 2010 and the engine didn't run since. Suggestions?

 

[Bondo]

Re: Mercruiser 4.3LX questions

I had the compression test done during inspection before I bought the boat. This was in Aug 2010 and the engine didn't run since. Suggestions?

Ayuh,.... 175 psi is New,... 150/ 145 psi ain't at all Bad,....

rebuild time is 100/ 110 psi....

 

[DeepBlue2010]

Re: Mercruiser 4.3LX questions

Thanks Bond-O. Can someone give me an estimate of the HP lost between 145 and 175 per cylinder?
I am replacing all the wood in the boat this winter with ? Marine Grade ply; also increasing the width of the stringers from ? to 1.5. With that said, I am a little worried about the added weight and if I will have enough HP to plane.

 

[Bondo]

Re: Mercruiser 4.3LX questions

Thanks Bond-O. Can someone give me an estimate of the HP lost between 145 and 175 per cylinder?
I am replacing all the wood in the boat this winter with ? Marine Grade ply; also increasing the width of the stringers from ? to 1.5. With that said, I am a little worried about the added weight and if I will have enough HP to plane.

Ayuh,.... So Don't over-built it so much....

1/2" deck, 'n 3/4" stringers is Plenty....