Overheated this weekend - 0 compression in 5 and 7

[pridekit]

The vitals:
2006 Launch 21V
Indmar Assault 325 - non-Cat (I believe) with half system
1890 hrs
0 Compression is cylinders 5 and 7.
All 8 spark plugs have some sort of dry black "dust" on them. Wipes off pretty easily, but comes back after running for just a couple of minutes.

What happened:
A couple weeks ago I replaced my alternator, I checked the belt to make sure it looked fine, no fraying or anything. Everything checked out and I installed the belt. I couldn't seem to get the belt tight so my friends and I got the bright idea to use a ratchet strap to tension the alternator. This past weekend I took the boat out, we were cruising a long just fine, I brought the boat down to an idle for a few minutes because I wasn't familiar with the water around me. I look down at my temp after I've been idling and I see the needle pegged. I shut the motor down and start checking everything. Eventually I see the alt belt in the back just laying their with teeth missing and split. I had purchased an extra belt, just in case (I had a gut feeling). I put the new belt on at the dock (after getting a tow back to the dock, and letting the motor cool down for a couple hours). I cranked the boat up and everything seemed good.

I took the boat out the next morning and after about an hour I started to notice white smoke coming from the exhaust. Got back to the dock and checked the oil, it looked clean, but had definitely burned some (it was full when I started the weekend, it was at half way on the dipstick). I checked for leaking around the manifolds, nothing there. Coolant levels looked good, temperature looked fine, oil pressure was starting to dip, but I assumed that was because of the decreasing oil level. So I decided it was time for a compression test. I pulled all of the plugs out and they were all black on the end (I'll take a picture in a couple hours). While I had them pulled, I had the motor cranked to make sure it didn't spit out any water or coolant, nothing came out.

I changed the plugs and cranked the motor up and waited for it to warm up. I gave it a little gas once it warmed up (around 2500 rpm for 10 sec), brought it back to idle, then shut it down and looked at the plugs. Black again. Back to the compression test. Port side (2, 4, 6, 8 ) were around 160, with 8 being 155. Starboard side was 1: 180, 3: 120, 5: 0, 7: 0. So, sounds like I've either warped my head or wrecked my gasket on the starboard side. I have a few questions though.

Questions:
1) has anyone replaced the head gasket on one of these Indmar motors? If so, any tips or things I should no before I dive in head first?
2) I don't understand why all 8 of my plugs were black on the end even after replacing them! Any ideas?
3) Should I replace both gaskets while I'm doing this work, or should I leave well enough alone on the port side?
4) Is there anything else that I have missed when checking? Anything I should check when I pull the heads off?

[mmandley]

Sounds like you blew the head gasket.

Heads on these boats are pretty straight forward, you will need the toque spec, intake, exhaust, and head gasket. I personally would do both if you that deep into the engine already.

You will need to send both heads in to get them milled and checked. Hopefully they can deck them and your good. You will also need to have the Block checked, thats a little easier, after its really cleaned and you green pad it down so there is no ols gasket or carbon, use a Steel ruler and feeler gauge to measure for flatness. I don't recall the tolerance but its not much.

Then just resemble and torque it all down. You might be able to contact SC for specs on this, or possibly Idmar as well. If you have no luck let me know I can ping a couple people I know to see if I can pull a favor on this.

If this was by engine I would totally do this myself, its really not that hard at all, just take your time, take pictures of before, label wires you remove.

DO NOT wait until next year to start this, if your leaking water into the cylinders they will rust and ruin the block, it will have to be bored out then. If you really cant do this right away then fog the block like your winterizing, then squirt a little oil into your cylinders to help keep the rust out.

I would budget about 800-1000 bucks on parts and head machine work. I would go ahead and get the heads rebuilt with new seals and seats while you have it at the machine shop.

[parrothd]

How many hours? 2000?

My guess would be stuck valves and or warped/cracked heads. Even with a cracked head you still should get some compression The gaskets and refurb heads aren't bad $$$ it's the labor and time.

Considering the hours on the motor you should look into a crate/reman block, I'm sure with those hours there probably other issues just waiting, plus the resale value would increase with a new motor...

I cracked the heads on my v8 jeep and replaced them, it wasn't a fun job, probably $1000 in parts..

[pridekit]

I'm going to tear into the bad side this weekend and see what it looks like inside. The major things to remove are exhaust, intake, valve cover correct? Do I need to pull the distributor as well?

I plan on doing all the work myself.


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[parrothd]

I'd leave the distributor... Probably need a service manual for the rebuild, take lots of pics helps..

[pridekit]

I'm hoping I can leave it, I have to reread the manual I found on bakesonline. I'll definitely take lots of pictures along the way. I'm hoping I can start it on Sunday. Unfortunately I can only work on it on the weekends :/

When I pull the head and expose the cylinders, I'm thinking I'll spray them with fogging oil and wrap the motor in plastic.


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[mmandley]

Are the block is open just wipe the cylinders with fresh oil. They will be fun. Stick towels in all open holes and rags in the cylinders to keep debris out.

Yes, remove intake, exhaust, valve cover head. Deff use a manual if you have access. Make sure you mark the head bolts, push rods, rockers, lifters. They need to go back in their original locations. They have a wear pattern on them.

No need to remove distributor unless it goes through intake manifold. I can't recall on that engine.

Also watch some basic videos on rebuilding sbc engines. They will give you some tips.

[mjr119]

The head bolts are torque to yield. They will need to be replaced.

[pridekit]

Good to know. Thanks mjr119


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[parrothd]

You should remove the 3 parts of the sunpad/engine cover/storage covers, save your back..;)

[moombadaze]

^^^^ agree with that--get as much vinyl out of the way as possible, possible tape towels in place to cover what you cant remove, your hands, arms and more are going to get dirty and just being close to the vinyl will get it dirty.

get some trays, plastic bags to put bolt and screws in to stay organized-label everything , makes going back together easier

[pridekit]

I forgot to include the spark plug picture.

23003

All the plugs had the same black powder, that one came out of #7 and has some gunk around the electrode. No other plugs have the gunk, just the black powder.

[parrothd]

:)

http://www.ebay.com/itm/New-5-7L-350-V8-Vortec-GM-Marine-Base-Engine-with-Intake-Replaces-Merc-1996-up/261722269581?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%2 6asc%3D33058%26meid%3D879e5b5af3c44b77a5f83bbf5350 317e%26pid%3D100005%26rk%3D4%26rkt%3D6%26mehot%3Dl o%26sd%3D181838619433 (http://www.ebay.com/itm/New-5-7L-350-V8-Vortec-GM-Marine-Base-Engine-with-Intake-Replaces-Merc-1996-up/261722269581?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%2 6asc%3D33058%26meid%3D879e5b5af3c44b77a5f83bbf5350 317e%26pid%3D100005%26rk%3D4%26rkt%3D6%26mehot%3Dl o%26sd%3D181838619433)

[mjr119]

:)

http://www.ebay.com/itm/New-5-7L-350-V8-Vortec-GM-Marine-Base-Engine-with-Intake-Replaces-Merc-1996-up/261722269581?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%2 6asc%3D33058%26meid%3D879e5b5af3c44b77a5f83bbf5350 317e%26pid%3D100005%26rk%3D4%26rkt%3D6%26mehot%3Dl o%26sd%3D181838619433 (http://www.ebay.com/itm/New-5-7L-350-V8-Vortec-GM-Marine-Base-Engine-with-Intake-Replaces-Merc-1996-up/261722269581?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%2 6asc%3D33058%26meid%3D879e5b5af3c44b77a5f83bbf5350 317e%26pid%3D100005%26rk%3D4%26rkt%3D6%26mehot%3Dl o%26sd%3D181838619433)


My god that is outrageous. But it is a NEW engine right? Not a reman?

Anyways. Look into doing a remanufactured block. If you decide to do a new engine that is.

MAABCO motors out of Texas shipped me a short block last year for $1000 flat. Comes with a 3 month warranty I believe.

[pridekit]

Yeah, that's new. I saw a reman motor for $2200. Michigan motorz has some new ones as well without the intake manifold, shaves a few hundred off.

I can save on the shipping with that one from Center State, it's only a couple hours away from me.

[parrothd]

Sorry, I didn't really look at the add, was just trying to make the point it's probably a lot easier to buy a block in the long run.. :)

[mjr119]

Yes it is easier. I did a complete reman build last year on a Centurion.

Reman short block from Maabco Motors - $1000 shipped
Refurbished heads local shop - $200 for a complete overhaul
New everything (Oil pump, timing cover, sensors, ex manifolds, all new gaskets throughout, new plugs, wires, distributor cap, coil, starter, relay, etc.)

All for around $2000. Didnt include labor obviously, but my labor is pretty cheap :)

Oh and definitely invest in an engine stand and some kind of hoist. I built the engine on a pallet lol, and hoisted it using a come-along in a tree in my yard. Pretty hood but hey it worked.

[mjr119]

Btw a local shop quoted me I think it was $7000 to do it all. I said heck no. So they pointed me to Maabco for the shortblock. They were definitely the cheapest REMAN place. Even after shipping.

[Fastest1]

Reading spark plugs with no load is useless.
A true plug chop is made on a clean new plug under a short burst of wide open throttle. Engine is killed while running WFO. Then read the plug.

[ranger098]

Maybe consider pulling the engine yourself, and bringing it to an engine rebuilder. Ya youll pay extra money, but itll be way less work and stress, and youll have a warranty on the work done. To me that would be worth the extra 1000 in labor. At least somewhere around that, its a basic job to a good engine rebuilder.

[pridekit]

Pulled the head today. Pictures to come. I don't think their is any scoring on the walls, I didn't see any or feel any.


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[pridekit]

Tapatalk was acting up Saturday night so I couldn't get the pics posted. But here we go:

23061

23062

23063

[pridekit]

#7
23064

#5
23065

#3
23066

#1
23067

[pridekit]

#7
23068

#5
23069

#3
23070

#1
23071

I forgot to mention that I dropped the head off at a local machine shop for them to look at and see if it is warped, cracked, etc.

[parrothd]

The only way you really know is via the machine shop. Should rebuild the heads while at it if they check out..

[pridekit]

That's the plan. Really just waiting to hear how bad the damage is and what cost to rebuild is vs buying a new one. The new ones aren't terribly expensive.


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[pridekit]

According to the machine shop the loss of compression came from the valve seats. They were corroding away and would no longer seal. They suggested that I replace both heads and the exhaust manifolds. I can't quite swing heads and manifolds, and feel that I can still get at least another year out of the manifolds (they are going on 2 years old right now). The suggestion for doing both heads came from the idea that it if it has corroded on one side, it is likely corroding on the other, and I'm inclined to only pull this motor apart once (preferably :p).

What is everyone's thoughts on this?

[pridekit]

Here are some pics from the shop (they are a couple hours away so I'm not able to take my own).

http://images.tapatalk-cdn.com/15/09/22/c34eb4e32355a4c992ad98dee1ff83bb.jpg

http://images.tapatalk-cdn.com/15/09/22/5e4a1613421e3aea51b43ff12cdacb72.jpg

http://images.tapatalk-cdn.com/15/09/22/b9ebf6e004506e666bc4a33fc0302cee.jpg

http://images.tapatalk-cdn.com/15/09/22/43bb035a2ff91cfeb0cf154087f6b683.jpg


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[parrothd]

Buy the new heads, when the engine fails use them on the new reman block...

I wouldn't be comfortable selling it, but I'd use it until it explodes.. :)

[Jason05216]

I know nothing at all about this so bear with me if this is painfully obvious but what causes the valves to do this?

[pridekit]

So water gets circulated through various passages in your engine to cool it, eventually that water has to leave. The water leaves through your exhaust manifolds, and is carried up through the riser and out through the exhaust ports behind your boat (if you have ever hooked up a fake-a-lake, or any other engine flush system and seen the water come out of your exhaust this is what I am referring to).

Apparently the water can actually get sucked up or trickle back into your cylinder heads. The manifold bolts to your cylinder head and pretty much exposes the top of the valve and the valve seat area. In my situation, I run in almost nothing but salt water, this will accelerate this corrosion process and when the salt water sits on the valve it will eat up anything around it. I flush the motor every time I am done using it, but you can never get all of the water out, you just hope you get as much as possible out.

[parrothd]

So water gets circulated through various passages in your engine to cool it, eventually that water has to leave. The water leaves through your exhaust manifolds, and is carried up through the riser and out through the exhaust ports behind your boat (if you have ever hooked up a fake-a-lake, or any other engine flush system and seen the water come out of your exhaust this is what I am referring to).

Apparently the water can actually get sucked up or trickle back into your cylinder heads. The manifold bolts to your cylinder head and pretty much exposes the top of the valve and the valve seat area. In my situation, I run in almost nothing but salt water, this will accelerate this corrosion process and when the salt water sits on the valve it will eat up anything around it. I flush the motor every time I am done using it, but you can never get all of the water out, you just hope you get as much as possible out.


Back in my Seadoo days I always had this issue, since they were 2 cycle motors water would sit in the exhaust system then moisture would rust the cylinders/bearings, it's worse with 2 cycle because there's no valves per say. You'd have to fog the motor after every use to keep this from happening.

Engines an water really don't mix.. :)

[Jordy Dag]

^^What this is referring to is called water reversion. Its alot of typing to explain but just google it and you will understand. If it were me, personally I would also replace the manifolds and possibly the risers. Typical manifold life varies depending on conditions, but with 2000 hrs on them and being possibly originals I would say theyve served you well and dont re use them. 2000 ish hours is alot and I would be replacing the entire engine. Throwing money away on an engine that is nearly at its life expectancy seems like a waste. I had a professionally reman 340 hp custom engine built for my last boat 2 seasons ago in miami complete for $3000 canadian. It came with a 24 month unlimited hours warranty and it was awesome. Still serving the new owner well. I have built many 350 sbc's over the years and couldnt buy the parts for that let alone the machine work I had done. Pm me and ill give you the info.

[pridekit]

They were replaced 2 years ago. I'd love to replace the whole motor, but it's a bit out of budget at this time. I have friends in the auto parts industry that are getting prices for new and reman heads. I'm also going to look at switching the manifolds into coolant cooled (like the rest of my block).


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[Jordy Dag]

I must be missing something... if youre block is coolant cooled then you are recircing a typical automotive antifreeze thru a heat exchanger with cold water passage on the opposite side of the exchanger thus descipating heat. Spent or heated water is then passed thru the riser to quench the exhaust so youre fiberglass exhaust system doesnt catch fire and burn your boat down. So, raw water is still flowing through the riser where gaskets are still prone to failure resulting in the same issue.... I guess what Im saying is you lost me...

[pridekit]

It's a half system. The antifreeze is passing through the block and heads. The hot water passes through the heat exchanger and into the manifolds rather than into the risers.

With the full system the manifolds are coolant cooled and a block off plate keeps the coolant from going into the risers. A separate line runs to the risers to expel it through the riser. I imagine there is still a risk of water reversion either way, but my manifolds run less risk of rusting out as quickly I suppose. It still amazes me that after 20 years we have not come up with a better cooling system for the exhaust :p


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[Jordy Dag]

I hear ya. I understand the half system and youre right I was referring to the riser gasket and reversion issue but I understand what you are saying now. You are after manifold longevity... ok im caught back up... carry on lol. And good luck