Need advise and your thoughts..

belliswood

Member
Nov 21, 2011
320
Colonial Beach, VA
Boat Info
1996 370 SUNDANCER
NAME: DAWG HAUS 3
Engines
7.4 EFI 454
V-DRIVES
I own a 1996 370 Sundancer with twin 7.4 EFI/MPI engines with 1100 hours on them. I purchased the boat in 2012 and every year when I do the oil change I have and oil analysis done. The only thing the oil analysis has revealed is trace amounts of antifreeze. The lab says not and issue but to keep an eye on it.

I am going to do the Great Loop in 2 years and was contemplating having the top ends redone on the engines. I believe that would take care of the trace antifreeze issue and give a boost to the engine performance somewhat.

So the question: would just doing the top end have any impact for me or should I just leave them be? any suggestions?

Thank YOu
Barry
 
I believe there is a coolant passage in the intake manifold on those engines.

It may just be a coolant leak from the intake manifold gasket into the crankcase.
 
This suggestion is strictly out of left field, but if I were serious about a Great Loop trip, I would try my best to find a 400, a 410 or even a 450 with 3116 Cat engines. You will burn about 1/2 the GPH compared to 7.4's. This is one of the very few situations where the cost of fuel alone may justify diesels. Then the continued maintenance is a lot less since the Cat engines have a 250 hour oil change interval.

Just a thought...........
 
I would do a leak down test and see the condition of the motors first - unlike a simple compression test, a leakdown will give you better data on ring and valve seal......as noted above, the intake and or gaskets could be a likely source of any leak......I would not just do the upper end if it is sealing well, often a new upper end can accelerate wear on an "old" bottom end (ring seal/blowby)
 
I have heard that doing just a top end sometimes on an older motor inadvertently puts pressure on the lower end something to do with the head gasket sizes and increasing the compression q sounds like you have some good running motor’s based on your information from the analysis I would leave well enough alone probably would be a good idea to stay on top of compression checks I think that’s always a great indicator of engine health
 
Thank You all for your response.

I would like to move up to a 450 but sadly I believe we will be keeping the boat we have. We do love it and it has been good to us.

A leak down test is a very good Idea. I will schedule with my mechanic once the boa tis in the water. Yes a Leak down would give good indication of the lower end condition.

So I guess I will leave things alone as far as the antifreeze issue. If it does get worse a gasket top end overhaul would be warranted.

Barry
 
I would not do the top end without doing the bottom end to. Joeyleggz is correct. The valves and rings wear and slowly leak compression. When you rebuild the heads, They no longer leak by, So now the rings are will either have to hold the extra pressure on the compression stroke or leak. Most of the time they will not hold and you will have a lot more blow by from the crankcase. My lesson learned from experience. This is why I bought a deisel boat, And reading Franks posts!!
 
This suggestion is strictly out of left field, but if I were serious about a Great Loop trip, I would try my best to find a 400, a 410 or even a 450 with 3116 Cat engines. You will burn about 1/2 the GPH compared to 7.4's. This is one of the very few situations where the cost of fuel alone may justify diesels. Then the continued maintenance is a lot less since the Cat engines have a 250 hour oil change interval.

Just a thought...........

I owned a 1995 37' DA with carbs for 12 years. I had Lowrance fuel flow meters so I knew my exact fuel burn and it was about 0.75 MPG. 40 DA with diesel gets about 1 MPG. But I agree with your suggestion to consider a 40/41. And for that trip diesels. Just your estimate of the fuel delta between gas and diesel is a bit off.
 
On cars at least, the old wisdom always said, 'never put fresh heads on an Old engine's. As others said, better sealing heads could cause more blow by on an engine with worn rings.
 
Kind of odd they would tell you your crankcase is making coolant but not to worry. Just keep taking samples?
Have you been adding coolant? Might want to try a different lab next go around.
 
If you take the rad caps off, warm the engines up while you watch the antifreeze you can some times see bubbles. If you see bubbles it is an indication you have a head gasket leak.
 
I'm not sure I like the advice of just watching it. In my experience a trace coolant leak into the oil can quickly evolve into all the coolant in your oil. This makes a mess of epic proportions and it something you don't want to have to deal with on a boat. I'd fix it.

Pete
 

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