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And the update. 

Unfortunately boats that sounds pretty good on the trailer frequently don't when they hit the water. That was the case this past Saturday. 

The carburetor is definitely fouled up. Without the secondaries open it doesn't have the hp to get up on a plane. And as soon as the secondaries open it leans out and falls flat on its face. The secondary jets must be stopped up. So, carb work is in order. Since there is a fair amount of corrosion on the carburetor and I have no doubt things will wring off, I ordered a rebuilt carburetor from a shop in Florida. As soon as it comes in I'll install it and hit the water again for some more engine testing. 

Under deceleration it is smoking a fair amount out of the starboard cylinder bank. It also has a lope atjust above an idle that makes me think it has a cylinder that is questionable. I'm going to do a compression test this week some time. Pulling the plugs should identify the culprit. It could have one that is oil fouling. If the compression checks good then I have a couple choices. Valve seals, or rings. Luckily, the price on the boat was low enough that if I have to go into the engine I'll still come out on top. I may throw a rebuilt engine at it and be done with it.

There was some good news. The transmission shifts like butter. I was very happy with its performance. I will go ahead and do a fluid swap on it this week and adjust the shift cable. 

Low speed handling is actually very good. I had zero issues getting it to go where I wanted it to.

No pictures, sorry. 

More to come. 



maj75 (Forum Supporter)
maj75 (Forum Supporter) HalfDork
7/5/20 9:46 p.m.

Inspect the oil pan.  They are notorious for rusting out on Shamrocks.  New risers?  Bad risers mean water makes it's way into the engine...  could explain your one bad cylinder if that has happened in the past.

In reply to maj75 (Forum Supporter) :

The new risers could be an indication of water damage, but they are a maintenance item on saltwater cooled inboards and IOs. We only get 4-5 years out of a set before they need to be replaced. He was also chasing a indicated high temperature problem and was throwing parts at it including water pumps hoses and thermostat housings. That turned out to be a faulty gauge, so it could be any number of things. I'm hoping for the best but prepared for the worst. I plan to get the compression test done this afternoon and work from there.

A rebuilt marine 302 long block is only about $1800-$2200 delivered. Since I plan on keeping this rig for a long time I don't mind throwing an engine in it. 



Toyman01 (Moderately Supportive Dude)
Toyman01 (Moderately Supportive Dude) MegaDork
7/11/20 12:40 p.m.

The verdict is in on the engine and it's not good. 

Starboard bank was the one that was smoking so I tested it first. 

 The front cylinder was 120. Not too shabby. 

The second cylinder was 30. sad I noticed when I pulled the plug that it was clean. That's usually a bad sign. 

The third was 60. 

The 4th was 90. 

I didn't even bother to test the rest of them. 

Now it's decision time.

Rebuild or buy a rebuilt? Buying a long block is probably what will happen.

Change to a Chevy engine? Tempting. Easier to make power. Easier to get parts. Full closed cooling system is available. More expensive than repairing what I have though. I would need a bellhousing and a full set of manifolds. 

More power? Probably not. 

Diesel? Oh so tempting. Big money though. Probably north of $5k assuming I could find a used engine and transmission. 




11GTCS Reader
7/11/20 3:30 p.m.

Just my opinion, that was pretty efficient power for that hull from what I remember.   A rebuild at the price you mentioned above seems like a bargain and everything bolts up.    You could probably even get it done in time to use it this year  

Straight inboards don’t always take to more power as readily as a stern drive boat; upper 30’s to low 40’s is usually the practical speed limit due to drag from the shaft and strut. That hull likely wouldn’t be super happy at those speeds anyway.   As far as closed cooling, if you’re mostly trailering and fit a fresh water flush connection onto the water intake you can flush it after every use on the trailer.   With a raw water shut off valve and fresh water available at a slip, you can do the same.     If you plumb the flush connection low enough it can also be used as an emergency bilge pump.  

In reply to 11GTCS :

I've been doing some reading. At about 35-40 the hull wants to ride up on the keel and fall over, so a speed demon it will never be. I'm looking for a 302 long block now and hope to have it in a week or two. It shouldn't take more than a weekend to swap everything out. 

The main reason I'm going to go with the closed cooling is to get the engine temperatures up. Raw water cooling in salt water means running a 150 degree thermostats to keep the block from absorbing the salt and rusting out. Closed cooling will let me run a 180-190 thermostat which will make the engine more efficient. I already have the parts to do that, that I robbed off of another boat. I'll install that stuff when I do the engine swap. 


11GTCS Reader
7/11/20 4:10 p.m.

In reply to Toyman01 (Moderately Supportive Dude) :

Oh, cool I missed that you had closed cooling parts.  No question that’s way better for the engine.  Good luck getting the long block.

Long block ordered. ETA 10 days or so. 

ultraclyde (Forum Supporter)
ultraclyde (Forum Supporter) UltimaDork
7/11/20 5:07 p.m.

Shame that you have to go that route but it's not bad money for reliability.  Single engine off shore isn't where you want to take chances, which I'm sure you know. 

plus a 302 will always sound better than a small block Chevy. 

In reply to ultraclyde (Forum Supporter) :

Even after buying the engine, I'm several thousand dollars below book value on the boat and many of them seem to sell for more than book. So worst case and I have to sell it, I should be able to get my money back out of it. 

The reliability will be super nice as well. 

ClemSparks UltimaDork
7/12/20 8:25 a.m.

Very cool.  (well...not the part where you have to buy or build an engine).  Looking forward to details on the closed cooling system.  I had a Volvo I/O that had a closed cooling system and loved it for the ease of winterization and not having Big Muddy silt flowing (hopefully flowing) through my engine.  

Toyman01 (Moderately Supportive Dude)
Toyman01 (Moderately Supportive Dude) MegaDork
7/27/20 12:23 p.m.

This guy showed up at the office today. Without stripping the plastic, it looks very good. The old engine is 8 bolts away from being removed. I should be able to get it pulled this weekend. Then I'm going to take a week to move all the accessories over to the new engine, redo some of the questionable plumbing, and clean the bilge while the engine is out of the way. I am also going to remote mount the oil filter so I won't have to change it while standing on my head. The transmission is going to get cleaned up and painted while I'm at it. 

metty New Reader
7/27/20 12:25 p.m.

where did you order the long block from? 

Toyman01 (Moderately Supportive Dude)
Toyman01 (Moderately Supportive Dude) MegaDork
7/27/20 12:38 p.m.

In reply to metty :

Atlantic Marine out of Miami. 


More forward progress today. 

Today was engine removal day. 

Unfortunate the top was in the way. Removing the front braces and the bolts for the rear legs let me tilt it forward enough to get it out of the way. 

The gantry I bought for rebuilding the lathe came in handy. It was just wide enough and tall enough to be perfect for pulling the engine. 

With all the boys helping, we had it out in under 2 hours. 


That may well be the problem with old engine. Looks like water got under the valve cover at some point and the valve is probably stuck in the head. Now someone explain why it wasn't rattling like a marble in a can. 


This is what it sounded like during the test run. I sure don't hear a any valve noise. I didn't when it was overboard either.



Figured out the lack of rattle. 

One of these is not like the other.

11GTCS Reader
8/2/20 6:41 p.m.

In reply to Toyman01 (Moderately Supportive Dude) :

Wait,what?  Some one pulled the pushrod on that cylinder?  Jeebus. 

In reply to 11GTCS :

It's still there. It looks like it jumped off the lifter and slid down into the lifter gallery.

captainawesome HalfDork
8/2/20 8:16 p.m.

So there's potential the engine isn't really too borked up?

In reply to captainawesome :

A very good chance. 

Does anyone have a T5 they want to part with cheap?


Found it!

Lots of rust in the top of the engine. 

The bottom end looks better. Looking at how clean the bottoms of the pistons are I don't think it has seen much run time. 

maj75 (Forum Supporter)
maj75 (Forum Supporter) HalfDork
8/6/20 4:50 p.m.

I've had a few inboard motors in salt water and never seen rust like that under the valve cover and valley.  I don't think that just exposure to salt air could rust internally that badly.  That looks to have had direct salt water in there.

smokeysevin New Reader
8/7/20 8:53 a.m.

In reply to maj75 (Forum Supporter) :

It could also be because there was water left under the engine cover in the engine bay and it sat over the winter in 100% humidity. That killed my dads boat...



smokeysevin said:

In reply to maj75 (Forum Supporter) :

It could also be because there was water left under the engine cover in the engine bay and it sat over the winter in 100% humidity. That killed my dads boat...



Looking at the condition of the bottom end, I'm guessing condensation from sitting for a long period of time. 

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