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NeilMcG View Drop Down
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    Posted: January-16-2023 at 10:29pm
Happy New Year!

'78 Nautique. The replacement engine core has finally made its way to the shop, so now it's time to focus on parts. The only decision so far is the use of Hypereutectic pistons, but everything else in the rotating assembly is still up in the air. Any options or comments regarding material alloys, design and even specific brands is helpful.

Thanks

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Tip #17 - Installing an expensive sound system does nothing to attract women to your boat. 
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MrMcD View Drop Down
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Points: 3590 		Post Options Post Options   Thanks (1) Thanks(1)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: January-17-2023 at 12:33pm
I will share a few good choices.
Pistons.  Federal Mogul,  Silvolite. Hypereutectics work great in these boat engines just don’t let the machine shop put them in too loose.   
Rings:   Hastings, Sealed Power or Mahle
Bearings:   Cam, Mains and Rods.   Sealed Power, Clevite.  Or Durabond for cam bearings only
Timing.  Cloyes
Oil Pump Melling
Gaskets.  Fel-Pro.  Spend the money for Marine the head gasket is tougher and stainless so it does not rust

That is how I would purchase.   I trust these brands to provide quality long lasting parts.
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KENO View Drop Down
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Points: 10640 		Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: January-17-2023 at 6:19pm
What are you calling a "replacement engine core" ?  A bare block that everything will be transferred to or something else.

Reusing the original crankshaft or is there a replacement?

You've come a long way from a couple of leaky speedometers Wink
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NeilMcG View Drop Down
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Very valuable. Thank you!
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NeilMcG View Drop Down
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Points: 200 		Post Options Post Options   Thanks (0) Thanks(0)   Quote NeilMcG Quote  Post ReplyReply Direct Link To This Post Posted: January-17-2023 at 7:09pm
Originally posted by KENO KENO wrote:

What are you calling a "replacement engine core" ?  A bare block that everything will be transferred to or something else

Reusing the original crankshaft or is there a replacement?

You've come a long way from a couple of leaky speedometers Wink

I actually have 2 engines now; the original and another from an '80 SN. The plan is to rebuild the 80 since the orignial 78 had so many overheats and other problems that I'm still in therapy for, it's not worth the risk. The 80 turns over ok so it's probably the better bet. But since its history is unknown, I want to have a list of all  possible replacement parts. Anything in good working order will be re-used except pistons and lifters, but it's also likely new stuff will be needed too. Paul turned me on to cam research, but for everything else, I have no experience with. The price disparity between different brands only adds complication.

Some days I wish I had those damn speedos back in so they could sink this sled.
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KENO View Drop Down
Grand Poobah
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Points: 10640 		Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: January-18-2023 at 11:41am
Originally posted by NeilMcG NeilMcG wrote:

 
I actually have 2 engines now; the original and another from an '80 SN.


 
Well at least both blocks are for 2 piece rear main seals and both crankshafts will have reverse rotation wick/helix lines to make your project easier..
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MourningWood View Drop Down
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Possible cringeworthy post ahead....

There is a quality machine shop near me. When the machining is done, he provides a "engine master rebuild kit" specifically for marine use. He is able to order the kit with bearings and pistons in the sizes needed. (only catch is the rr cam and seals, if needed)...
I assemble the motor and so far (4 351W and 7 Saturns) it works out very well, and it keeps the cost way, way down compared to ordering everything individually. 
1994 Ski Nautique "Riot"
1964 Dunphy X-55 "One 'N Dun"

'I measured twice, cut three times, and it's still too short!"
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NeilMcG View Drop Down
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Points: 200 		Post Options Post Options   Thanks (0) Thanks(0)   Quote NeilMcG Quote  Post ReplyReply Direct Link To This Post Posted: January-18-2023 at 12:15pm
Originally posted by KENO KENO wrote:


Originally posted by NeilMcG NeilMcG wrote:

 
I actually have 2 engines now; the original and another from an '80 SN.




 
Well at least both blocks are for 2 piece rear main seals and both crankshafts will have reverse rotation wick/helix lines to make your project easier..



This is EXACTLY why I created this thread. Thanks Ken.
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Fl Inboards View Drop Down
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Points: 2065 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Fl Inboards Quote  Post ReplyReply Direct Link To This Post Posted: January-18-2023 at 5:24pm
First think you must ask your self is what are you going to do with the boat? Few blasts on the lake a year?
or a  dozen ski days a month  for 6 months.
78 ski nautique meh! i see the prior!
If your building for resale  goodluck on the towboat rollercoaster.
making a flatbottom ski boat go real fast is not a good idea. well at least for most.
50 Mph? good safe goal.
GT-P heads, or at least gt-40 heads, 10-1 pistons and a slightly bumpy camshaft as to not screw with good idle. match port a dual plane manifold as well as match port exhaust to head flanges turn it 5100 rpms. good ignition system should run 50 mph.. Good safe goal.
Hobby Boats can be expensive when the hobbyist is limited on their own skill and expertise.




1993 Shamrock "fat" 20. 2008 Nautique 196 5.0
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NeilMcG View Drop Down
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Points: 200 		Post Options Post Options   Thanks (0) Thanks(0)   Quote NeilMcG Quote  Post ReplyReply Direct Link To This Post Posted: January-18-2023 at 6:13pm
Originally posted by Fl Inboards Fl Inboards wrote:

First think you must ask your self is what are you going to do with the boat? Few blasts on the lake a year?
or a  dozen ski days a month  for 6 months.
78 ski nautique meh! i see the prior!
If your building for resale  goodluck on the towboat rollercoaster.
making a flatbottom ski boat go real fast is not a good idea. well at least for most.
50 Mph? good safe goal.
GT-P heads, or at least gt-40 heads, 10-1 pistons and a slightly bumpy camshaft as to not screw with good idle. match port a dual plane manifold as well as match port exhaust to head flanges turn it 5100 rpms. good ignition system should run 50 mph.. Good safe goal.


This isn't going to be a high performance build. The intended use is that of most every other sn. Lots of skiing and general enjoyment of the lake. Luckily I already have heads in great shape so unless the GT fairy lays a pair on my door, I'm going with what I have. RPM is def going to less than 5,000. The only real worry I have is making sure sound reliable parts are used for the rotating assembly. I already have an edelbrock 2181as well.
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DW1 View Drop Down
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Points: 21 		Post Options Post Options   Thanks (0) Thanks(0)   Quote DW1 Quote  Post ReplyReply Direct Link To This Post Posted: February-09-2023 at 1:23pm
Just a bit of food for thought.  The era of 250+/- hp ski boats met the goal of being useful ski boats.  The era of 300 hp boats did really improve the ski experience specifically when pulling up a slalom (single ski) skier.  The additional hp really cut back in the 'pop out of the water' distance.  Long gone are the days of dropping a ski once out of the water with the more locked in bindings. 
The hp gain was in the airflow area, both GM and Ford cylinder heads (Vortec / GT-40) were the keys.  You can sort of substitute the heads with a more aggressive camshaft or maybe rocker arm ratio if you want to pursue some additional hp.  Good luck and happy boating once it drops in the water.
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NeilMcG View Drop Down
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Points: 200 		Post Options Post Options   Thanks (0) Thanks(0)   Quote NeilMcG Quote  Post ReplyReply Direct Link To This Post Posted: February-09-2023 at 4:01pm
[QUOTE=DW1] Just a bit of food for thought.  The era of 250+/- hp ski boats met the goal of being useful ski boats.  The era of 300 hp boats did really improve the ski experience specifically when pulling up a slalom (single ski) skier.  The additional hp really cut back in the 'pop out of the water' distance.  Long gone are the days of dropping a ski once out of the water with the more locked in bindings. 
The hp gain was in the airflow area, both GM and Ford cylinder heads (Vortec / GT-40) were the keys.  You can sort of substitute the heads with a more aggressive camshaft or maybe rocker arm ratio if you want to pursue some additional hp.  Good luck and happy boating once it drops in the water.
[/QUOTE
]

You make some good points...got to some thinking now. My outlook is that the higher hp ratings came in response the needs of wakeboard boats and their ballast tanks. The 70's nautiques are incredibly light, and motors like the pcm model 250, rated at 240 hp is plenty of power for any type of skiing. This isn't my boat. It's for a friend and I'm doing it all out-of-pocket so maybe small things to improve performance might be worth considering, but it's unlikely that I'll go with performance heads or any of the exotic stuff..
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