Hey guys, I have a 1978 18.5 ft Hallett mini day cruiser with a stock 460 ford and a Berkeley JC. I bought it from the original owner at the end of last year. It runs and is in overall great shape. When I got it home I noticed that not a lot of water was running out of the port side exhaust. I pulled the water lines off the snails and found what appeared to be sand and calcium in the line coming out of the bottom of the port side snail and very little sand out of the starboard side. Once replaced the water hoses I had a lot better flow out of both exhaust tubes. With everything looking good I took it for a spin at my local lake.

Once I got it out on the lake it ran great for about 25 minutes. Then all of a sudden I noticed a decrease in propulsion and my temp gauge starting to rise. I immediately backed off the throttle and headed toward the ramp. By the time I got close to the dock I had practically no propulsion and the engine had reached a temp of 225. from the time I initially noticed a problem to the time I shut it down and pulled it out was around 10 to 15 minutes. I pulled it out and went home.

After I got home I opened the hand hold and noticed a little bit of grass wrapped around the impeller shaft. Worried that the overheating blew a head gasket I checked the oil on the dip stick and found no milkshake. I also pulled all the plugs and checked for water. I found no water in any of the cylinders. I then did a compression check on all the cylinders and came up with the following:

1.  115           5.  60
2.  118           6.  80
3.  120           7.  80
4.  125           8.  50

cylinders 5-8 are all on the port side and are obviously significantly lower. What do you think would cause the entire port side to have such low compression? I was hoping to get some feedback from you guys before I tear into it. Thanks in advance!

 

Hey guys, I have a 1978 18.5 ft Hallett mini day cruiser with a stock 460 ford and a Berkeley JC. I bought it from the original owner at the end of last year. It runs and is in overall great shape. When I got it home I noticed that not a lot of water was running out of the port side exhaust. I pulled the water lines off the snails and found what appeared to be sand and calcium in the line coming out of the bottom of the port side snail and very little sand out of the starboard side. Once replaced the water hoses I had a lot better flow out of both exhaust tubes. With everything looking good I took it for a spin at my local lake.

Once I got it out on the lake it ran great for about 25 minutes. Then all of a sudden I noticed a decrease in propulsion and my temp gauge starting to rise. I immediately backed off the throttle and headed toward the ramp. By the time I got close to the dock I had practically no propulsion and the engine had reached a temp of 225. from the time I initially noticed a problem to the time I shut it down and pulled it out was around 10 to 15 minutes. I pulled it out and went home.

After I got home I opened the hand hold and noticed a little bit of grass wrapped around the impeller shaft. Worried that the overheating blew a head gasket I checked the oil on the dip stick and found no milkshake. I also pulled all the plugs and checked for water. I found no water in any of the cylinders. I then did a compression check on all the cylinders and came up with the following:

1.  115           5.  60
2.  118           6.  80
3.  120           7.  80
4.  125           8.  50

cylinders 5-8 are all on the port side and are obviously significantly lower. What do you think would cause the entire port side to have such low compression? I was hoping to get some feedback from you guys before I tear into it. Thanks in advance!

This has me going down two completely different roads.

The first road is could be a failed head gasket.  It would be weird, but hey.

The second road would be valve adjustment. Reaching there two.


Stupid question of the day.

Did you have the throttles opened all the way for the test?  Did you do port first? Fuel washed?

Wet it up with some oil and do it again.

GT

I'll agree to some extent with Glenn.   You measured the "good" side first.   I'll disagree about oiling 'em up, that will give you a false positive.   Disconnect the pump, or back it into the water, get it fired and up to temperature...you may need oil in the cylinders to make compression to get it hitting on all 8, but that will be gone after a few minutes of running.   Then do another compression test.   Get a charger on the battery, hold the throttle wide open, disable the ignition.   The goal is to have the same cranking speed on every cylinder and no fuel to wash the cylinders down or sparks to surprise you.   Running the engine will condition the cylinder walls appropriately for meaningful test results.

My thought on a tad of oil will tell you if the head needs to come off is all.

I like your method better.  I'm a little more down and dirty.

GT

i'm a little more lazy, and too cheap to buy head gaskets ifn I don't need 'em

I was thinking head gasket but wouldn't it seem weird that all 4 cylinders would be lower in comp and not have any water in none of them?  What about a warped head?

Additionally could you get the boat up to temp in the drive way hooked up to water to test the comp for the warm compression test?  Instead of disabling the pump or backing it back in the lake?


----------------------------------
Last night....I was drunk for a week.

Kinda sorta.

Let me guess,  three point mounts?

If you got it hot enough,  you could have blown the web between cylinders.

You have to remember,  this is not a car and there is no cooling system pressure without the engine pulling a load.

Good luck.

GT

No V8 can lose the fire rings between all 4 cylinders on one side simultaneously. While it's not impossible, I can't see how it's possible.   

Do a compression text properly and it will tell the story.

Edit...the only reason I said to run it up to temp was to condition the cylinder walls and burn off fuel/reestablish the oil film so your test results are more useful.   Temp makes no difference since it's a comparative test

It only has to do it twice.

And you're wrong. I've seen it.  5-6 and 7-8.

Happened due to what I believe to have been a severe case of hydraulic action from a cracked exhaust manifold.

GT

Sent from my SCH-I545 using SoCal Jet Boats mobile app

Thanks for the feedback. Sounds to me like I need to re-due the compression test. I did it cold with the throttle in neutral. If I don't add a little oil to the cylinders and have the throttle wide open and fuel wash is a concern would I still get an accurate test? Do I need to run the motor between each cylinder test?


Sent from "The Brown Chair"

You must be a ford guy

Nope,

Been called much worse by better people. Hahaha

Just smart enough to know we were talking blue oval.

Then learn your damn cylinder positions

Edit.  Lol...did' even realize we were talking about ferd.   I just looked at it as basic diagnosis.

Immma put this in the win column.

It's pretty much how I roll.

Besides,  sometimes when you speak Chevy to a Ford guy they get confused,  you know,  like when you say start it up and run it.

That's completely foreign to most Ford dudes.


DOH!

GT

Ha! No problem at all. I appreciate all you guys and your willingness to get in the trenches to help a guy out! 👊🏼 I got called into work but when I get home I'm gonna try the test over again. I really hope it's just a cooling problem.


Sent from "The Brown Chair"

Take a look at both cylinder heads casting numbers and see if they match...it is a nearly 40 year old boat/motor

Big chamber/small chamber mismatch?

Dan'l

Good call.

Immma put this in the win column.

It's pretty much how I roll.

Besides,  sometimes when you speak Chevy to a Ford guy they get confused,  you know,  like when you say start it up and run it.

That's completely foreign to most Ford dudes.


DOH!

GT

Right when I was kinda startin to like you and your old man wisdom....😏

Did the leak down test get done yet? If so what were the results?

Shawn