980 hours on engines - compression test

[Scott Danforth]

Moat salt water boats with low hours and rebuilt motors are marina dock queens and the exhaust rotted out requiring a rebuild

 

[achris]

Moat salt water boats with low hours and rebuilt motors are marina dock queens and the exhaust rotted out requiring a rebuild

Agree... Low hours does not always equal a good thing in boats...

When I was servicing outboards, we had a couple of local fishing companies as clients. A very rough 20hp outboard or 2 would arrive in the workshop for a 6 month service. You could see that this engine was worked hard, and put away wet, EVERY DAY! But every bolt unscrewed easily, and it just required new gear oil, pump impeller, spark plugs and a fuel filter clean and it was running like new again. These engines has THOUSANDS of hours on them... The other side of the coin was customers bringing in the outboard that only got use at Christmas. :facepalm: These engine were a nightmare. Every bolt fought all the way out, the fuel systems were gummed up, the impellers were cracked and broken, steering and tilt pivots were seized... Never liked seeing a 15 years engine with 40 hours on it in the shop!

Chris............

 

[tpenfield]

The nice thing about my boat is that it has been used pretty consistently throughout its life. About 40 hours per year. I am the 4th owner, having owned the boat for 6 years now. The PO, 3rd owner, only had the boat for a couple of years. So, the first 2 owners split the first 14 years (+/-). All 3 of those owners were Lake Winnepesaukee, NH.

The boat did not see salt water until I bought it. The engines have never seen salt water, because of the closed cooling that I added.

 

[Scott Danforth]

The nice thing about my boat is that it has been used pretty consistently throughout its life. About 40 hours per year. I am the 4th owner, having owned the boat for 6 years now. The PO, 3rd owner, only had the boat for a couple of years. So, the first 2 owners split the first 14 years (+/-). All 3 of those owners were Lake Winnepesaukee, NH.

The boat did not see salt water until I bought it. The engines have never seen salt water, because of the closed cooling that I added.

if it was my boat, I would do nothing more than pulling the heads, inspecting the bores (above the pistons with a bore gauge for diameter and run-out)

then I would do some mild porting and bowl blending to remove casting flash, port match the exhaust, get a valve job and bolt the heads back on and go boating.

(and yes, the evil little guy on my shoulder is saying "build a pair of 540's however the realist in me is saying cant do anything until you pull the top end and look)

 

[Bondo]

having owned the boat for 6 years now.

Wow,..... Hard to believe it was that long ago, you were up here lookin' at Chris' boat, 'n stopped by,.....

 

[tpenfield]

Wow,..... Hard to believe it was that long ago, you were up here lookin' at Chris' boat, 'n stopped by,.....

Yup, seems like just last week. I remember that summer, looking all over the Northeast for my 'next' boat, which is now my 'getting old boat' .

Maybe when I'm in the market again, there will be something up your way :thumb:

 

[tpenfield]

if it was my boat, I would do nothing more than pulling the heads, inspecting the bores (above the pistons with a bore gauge for diameter and run-out)

then I would do some mild porting and bowl blending to remove casting flash, port match the exhaust, get a valve job and bolt the heads back on and go boating.

(and yes, the evil little guy on my shoulder is saying "build a pair of 540's however the realist in me is saying cant do anything until you pull the top end and look)

Yes, I think the heads are a definite, then the rest will be decided based on measurements and tolerances.

 

[Rick Stephens]

I've enjoyed this thread enormously. I never really thought about the unique, and potentially expensive pitfalls, of maintenance on 1000 hour motors that might be sold. Great input from some knowledgable folks. Made me sit and think about things. Learned a few things, I might add. Thanks!

Rick

 

[tpenfield]

I've enjoyed this thread enormously. I never really thought about the unique, and potentially expensive pitfalls, of maintenance on 1000 hour motors that might be sold. Great input from some knowledgable folks. Made me sit and think about things. Learned a few things, I might add. Thanks!

Rick

Me too, learned a bunch of stuff throughout the process so far.

1) Engines will go 2,000 - 3,000 hours before really needing a rebuild as long as maintenance is attended to.

2) Engines might need a valve job at 1,000-1,500 hours

3) 1,000 hours on an I/O has some market perceptions. Not sure how real they are.

4) I was surprised to learn that the std Mercruiser cam has almost NO valve overlap. I guess they are not taking any chances with reversion at idle speeds.

5) Now when I see someone talking about installing a jacked-up cam in their I/O I can have a stronger sense of the trouble it probably will bring. . . . BTW - Does anyone remember the guy who did a high performance rebuild on a 4.3 V6 I/O a few years ago (maybe longer). IIRC he was using a performance cam against the advice of many. We never heard much from that guy after he was all done. I don't remember his Name/handle :noidea:

6) Tolerances for crankshafts, cams, and cylinder bores are in the 0.001" range, as low as 0.0004" for original production parts.

7) I did not realize the flat lifter cams had a taper designed into the lobes.

8) If it ain't broke . . .​

Not sure what else . . .

Of course, in my previous experience doing just a valve job on the 454 in my 24 foot cuddy (Formula 242), I did get some critique after the fact of possibly shortening the life of the lower end of the engine, now that I had fixed the top end.

Not sure if I should keep #8 above in mind when I do a valve job. :noidea:

 

[hoowahfun]

You could always sell it now and save yourself the hassle of a rebuild...plus 980 hours sounds better than 1000+ wouldn't hurt to put the feelers out there...if nobody bites at the price you want then you could move forward as planned.

 

[Lou C]

I guess the issue of doing just a valve job, could be considered after doing a leak down test. If acceptable leak down was found, or the leakage was due to valve sealing, not piston ring/cylinder wear, then just doing a valve job might not be risky eh? I basically did the same thing with re-man heads, have not really run it enough that any problems would be manifest, but at this point whatever I get in terms of longer use is all good....(30 year old short block lol)….

 

[tpenfield]

Good point, Lou. Probably a leak test would be in order once I got the engines out of the boat and before I loosened any bolts. Then I could get an idea of how much leak is valves vs. rings

 

[Scott Danforth]

I believe it was Tail gunner that built the 4.3 back in 2009. he had a thread on the hotrod forums as well as here.

I ran into reversion at idle with my build. I built a custom exhaust with a cross-over to take care of that gremlin.

 

[tpenfield]

There was another guy that Tail Gunner helped with a 4.3 rebuild, after he had finished his own. The guy didn’t stick around though.

 

[Rick Stephens]

Seems to me, that if you want high performance, swap to a V8. The cost to add performance stuff to a V6 quickly exceeds its value in a boat. Jumping to a 5.7 or 6.1 would surely be a more cost effective way to jump the shark.

 

[achris]

Seems to me, that if you want high performance, swap to a V8. The cost to add performance stuff to a V6 quickly exceeds its value in a boat. Jumping to a 5.7 or 6.2 would surely be a more cost effective way to jump the shark.

Yes and no. The 'price' of the V8 over the V6 is about 100kg. In a small boat, that can be significant... Particularly in a stern drive configuration, with all the engine weight at the back.

Chris......

 

[harringtondav]

Yes and no. The 'price' of the V8 over the V6 is about 100kg. In a small boat, that can be significant... Particularly in a stern drive configuration, with all the engine weight at the back.

Chris......

True that. My 4.3 shoots my 'lil boat out of the water. But in slow speed chop management, that extra stern load just worsens the hammering.....Although the good times beat the 3.0L.

 

[Scott Danforth]

There are 4.3s with superchargers.....about 350hp

 

[tpenfield]

There was another guy that Tail Gunner helped with a 4.3 rebuild, after he had finished his own. The guy didn’t stick around though.

Found it Member’s name RSBJ Rebuilt his 4.3 into a high performance version.

https://forums.iboats.com/forum/eng...ing-a-1998-mercruiser-4-3l-need-advice-please

 

[Rick Stephens]

Found it Member’s name RSBJ Rebuilt his 4.3 into a high performance version.

https://forums.iboats.com/forum/eng...ing-a-1998-mercruiser-4-3l-need-advice-please

I remember that thread.... RSBJ was a bit on the prickly side. Did NOT like being told no, ever.

I also believe static water line is mostly meaningless. Every boat behaves in its own way in rolling water and while in use - if you give an engine the cam to enable reversion, it will, regardless of what the static level is.