Just can't win :(

[Scott Heidt]

Hey guys I just can't seem to win!

I have been working on restoring my '81 Hornet for two years. It had a rebuilt 454 when I bought the boat. During the first water test in January, 20 min into it, we threw two rods and sheared the cam in two places.

Bought a new 502 long block, All we had to do was install the new intake manifold, exhaust manifolds, water pump, dist, etc.
Cranked it up and everything seemed fine. Adjusted the timing etc. Couldn't seem to get it to run properly. We started to try and track down the problem. Water in the fuel, fuel pump problem, carb. issue, distributor problem. The main thing was that on the trailer it seemed tohave plenty of power. You get it in the water and it wouldn't go over 3800 rpm and then the power would drop to 3100 rpm. Like it was starving for fuel. Then at Mount Dora it ran terrible. On the way back to the boat ramp it was sputering like water was in the fuel. We'll we pulled the intake manifold and the oil on the top of the block was milky. The oil in the pan seemed ok. My uncle is pulling the valve covers today but there appears to be water in there also. The intake gasket looked fine and the manifold looked good. The exhaust manifolds are band new (stainless marine). He is pulling those also.

If all that checks out, is it possible that maybe there might be a defective headgasket, head, or improper factory assembly. I will post updates. My uncle is a good Merc. mechanic. He has been doing this for a long time. I rather a novice, but am learning from him. I thought I would post this to get some input from the group. I know there are many members with a vast array of knowledge. Comments and help are very much appreciated. I just want to go boating! Feeling a little frustrated, but I won't be beat. I have been around boats all my life and know how it goes. :banghead:

[rayjay]

What 502 Long Block did you buy?

rayjay

[MOP]

All of what you mentioned are good possibilities, also take a good look at the intake manifold gasket by the water passages. I had that drive one of our guys crazy after a leak down test showed no leakage he was going to pull the heads but by chance saw the water track mark, the block water pressure can get pretty high when running and can spray water into the valley if the gasket is not making a good seal.

That still does not explain the poor running condition, which I think is a top end issue.

Phil

[Scott Heidt]

All of what you mentioned are good possibilities, also take a good look at the intake manifold gasket by the water passages. I had that drive one of our guys crazy after a leak down test showed no leakage he was going to pull the heads but by chance saw the water track mark, the block water pressure can get pretty high when running and can spray water into the valley if the gasket is not making a good seal.

That still does not explain the poor running condition, which I think is a top end issue.

Phil

I saw a water mark on the gasket. I will try to post a pic of the water mark. It is hard for me to get to the shop during the week. Good thought though! Another member asked what gen the engine is? I am not sure my uncle has the paper work at the shop. All I know is that it is brand new, so I would assume that it would be the most recent Gen 502. :bonk:

[Digger]

Scott, sorry to hear of your troubles. Keep up the good attitude and hang in there. Is this a carb motor or MPI?

[rayjay]

Another member asked what gen the engine is? I am not sure my uncle has the paper work at the shop. All I know is that it is brand new, so I would assume that it would be the most recent Gen 502. :bonk:

There are a number of 502's besides just Gen V and Gen VI. They differ in intake, head and cam as well as whether they were for auto/truck or marine use. I am interested in this thread as I am starting with what appears to be a non-marine engine. I will know exactly which one as soon as I can really examine and measure the pieces. What you find out will help me learn about my combo and what I will have to do.

rayjay

[Cuda]

I'm betting on the intake gasket. A freind of mine had the exact same problem on his. He installed a water pressure regulator that dumps water if the pressure gets too high.

[BERTRAM BOY]

Could there be a crack in the intake manifold?

[Scott Heidt]

Scott, sorry to hear of your troubles. Keep up the good attitude and hang in there. Is this a carb motor or MPI?

Carb. Holley 750

[Scott Heidt]

There are a number of 502's besides just Gen V and Gen VI. They differ in intake, head and cam as well as whether they were for auto/truck or marine use. I am interested in this thread as I am starting with what appears to be a non-marine engine. I will know exactly which one as soon as I can really examine and measure the pieces. What you find out will help me learn about my combo and what I will have to do.

rayjay
It is a marine 502. My uncle bought it from Daddy O's Marine in Pompano. I will find out the particulars.

[Scott Heidt]

Could there be a crack in the intake manifold?

It doesn't appear that there is a crack. It is brand new, but there could be a defect when it was cast. We only did a visual inspection at this time until we do a little more investigation.

I am honestly hoping that it is a head gasket, head or something else that would allow us to just send the engine back and exchange it for a new engine or if it was a factory defect of the new intake manifold or exhaust manifold that would allow for some type of recourse with repairs. If it was something we did (ie. gasket not seated right, etc.) then it is on us. :shocking:

The saga continues! Stay tuned :outtahere

[Jamesbon]

If it helps, keep your head up, you'll win this one.

Ditto what MOP and CUDA said about the intake/head/gasket mating surfaces.

Also, please consider the services of Dean Nickerson in the carburator department. They are second to none in their carb. prep. Prepare to pay a couple to three bills in their bench testing and modification services. http://www.nickersonperformance.com/marine/marine.html

You can also H2O test your exhaust set up outside of the boat with a little duct tape and garden hose....just ask how I know this one...

Your boat is beautiful and representative of the hard work put into it, I drooled @ Dora!! (reminds me of what my GT will look like... :)

[Fish boy]

Your boat is beautiful and representative of the hard work put into it, I drooled @ Dora!!

I totally agree with Nate. Just keep chippping at it, pretty soon you will find the gremlin. Clearly too much hard work put into what is IMHO one of the benchmark donzi's on this site.

Fish

[RickR]

Although your 502 should be a Mark VI there is a issue with a
Gev V (1989/1995) block and early pre 1989 heads. Possible leak.
Chevorlet addressed this problem and supposedly it in not an issue in Mark VIs.

Dennis Moore's "Big Block Marine Performance" discusses the problem.

GOOD LUCK!!!

[MOP]

Scott and Old Fart Trick, put about 3-4 ounces of Simple Green in with the first "cheap oil" change run at high idle 1000-1200 for about 30 minutes, drop the oil and filter then put the good stuff in. You run in salt, bad enough having a tad of fresh water stuck in some obscure place that did not mix in but salt sneaks up on you later.

Phil

[Scott Heidt]

Scott and Old Fart Trick, put about 3-4 ounces of Simple Green in with the first "cheap oil" change run at high idle 1000-1200 for about 30 minutes, drop the oil and filter then put the good stuff in. You run in salt, bad enough having a tad of fresh water stuck in some obscure place that did not mix in but salt sneaks up on you later.

Phil

Thanks! That was going to be one of my questions once we figured this thing out. Sounds like a plan!

[Cuda]

I run half diesel and half oil to cut the emulsified oil out of the engine. Works great.

[DUCATIF1]

Sorry to about your string of luck but I am curious how there is water on top end but not in pan when you said boat was run for some length of time which would circulate any water problem related to a head gasket or most intake gaskets into pan area. I know nothing about boats recirculating coolant and I am sure there are a lot more qualified guys out there than me but..... Possible if this is fuel injected motor that there is leak in throttle bodies water passage if so equipped? GM on there auto line run water through TB for winter conditions. I had a problem with aftermarket TB set up with similar condition. Was a bitch to track down. I have seen guys pull apart auto motors without fully draining them revealing what they think is coolant related gasket problem that they caused during disassembly. I would look towards your initial thought of water in fuel system. Is there a way to recirculate water with dye in system as is done in auto type closed system?? Good luck and like I said just my two cents. In the end I hope it is quick inexpensive repair.

[Scott Heidt]

I run half diesel and half oil to cut the emulsified oil out of the engine. Works great.

Thanks! Cuda! I need all the help I can get! Ha!

[RickR]

FYI
Is in common to have moisture under the valve covers during cool weather and short runs when your oil doesn't get up to temp.
Everyone with a high performance engine should have an OIL TEMP GAUGE :yes:

[BUIZILLA]

Wrong head gaskets. Get a GMHPP book and you'll find the correct part numbers in there.

J

[gcarter]

Wrong head gaskets. Get a GMHPP book and you'll find the correct part numbers in there.

J
Jim;
I'm glad to here from you!! :)
George

[Scott Heidt]

Wrong head gaskets. Get a GMHPP book and you'll find the correct part numbers in there.

J

Hey Buizilla! Good to hear from you!

Man I hope that is it, because then it would be on the company I bought the engine from. The engine is a new long block. We purchased it about 2 months ago from Daddy O's Marine in Pompano.

My worst fear is that the problem would be from a gasket that we installed (ie. Exhaust manifolds, Intake manifold, etc.

I'll post updates as soon as I can. Thanks for your input. :wavey:

[BUIZILLA]

Was it a marine specific 502 longblock? or a GM crater? very important info here... GEN IV,V,VI ? heads match the block generation?

J

[Scott Heidt]

[QUOTE=BUIZILLA]Was it a marine specific 502 longblock? or a GM crater? very important info here... GEN IV,V,VI ? heads match the block generation?

Hey Buizilla

Thanks for your input! I have good news of sorts. We pressure tested the intake manifold and the exhuast manifolds and they all checked out. We also did a compression test.

L---------Bow----------R
125 125
120 125
70 50
120-------Stern--------120

We are now thinking head gaskets also! Buizilla I think you nailed it on the head. Thank you for taking the time to give your input. I will keep everyone updated. The good news is that it is a new engine and this is looking more and more like a warranty issue!

My uncle said that this was a marine 502 long block. HE is the mechanic in the family. I am but a mere apprentice! :) But I seem to be learning all this stuff the hard way! HA! But I'm learning!

Thanks again !

[BUIZILLA]

Hmmm, you lost the same opposed holes on each side.... there's gonna be more to this story.

J

[DUCATIF1]

I know I am outsider her but I am curious as to how you have low compression on either bank? You also explained that there was no water in the pan after running for what sounded like an extended period of time? That would be some coincidence to blow both gaskets unless they were indeed wrong as indicated possible by the above? I am no BBC expert as I a SB person but are those two intake runners close to a water passage? Possible leak from manifold into cyl causing additional damages?? Please these are just my ideas as I love any post that has perplexing mechanical problem. Unfortunatly it is yours and I hope it is a cheap resolution. Leak down test performed on those cylinders??
Also from dealing with dealership warranty issues I hope you have someone from either warranty co or dealer looking at that thing BEFORE you play with it any further. I know I would never pay for anything if it wasn't disassembled in front of me. You may trust your relative but it will mean nothing to them. Good Luck

[Rootsy]

now that's soemthing i can honestly say i have not encountered before!

[Scott Heidt]

Point Taken. Yeah we aren't going any further. Tomorrow we are going to call the Company that we bought the engine from to see how we are going to handle this. I want to make arrangements to take the engine down to them so we can have them pull the heads in front of us to investigate further.

I figure that you have to be very careful with a possible warranty issue. Thanks for your input. This will be interesting for sure. We should have a little contest to see who is the best prognosticator as to the final cause of the water intrusion into the engine.

Later!