420 Aft cabin underpowered?

cigars01

cigars01

Member
Sep 1, 2016
124
Lake Lanier,Cumming Ga
Boat Info
1981 Searay 310 Vanguard Express Cruiser.
Engines
Twin 454 Crusaders Direct Drive
I am looking at buying a 1996 420 Aft Cabin. The boat is powered by the base 7.4 merc engines which I believe are 340Hp each. The engines from service records have been well mainitained and have 635 hours. I boat on Lake Lanier, Ga. My question is: are those engines enough power for that boat?

Seeing the configuration of how the engines are installed, if you had to repower or pull the engines for any reason, is it possible withoug doing surgery to the salon floor or cabin etc?
 
The trusty 7.4's are more than enough for a 400DA. I guess the only downside to the aft cabin is that it's heavier and the weight is further astern. My experience is that the gas powered 400DA is perfectly balanced, much better than the 340 I had with the same power.
 
Stee6043 said:
The trusty 7.4's are more than enough for a 400DA. I guess the only downside to the aft cabin is that it's heavier and the weight is further astern. My experience is that the gas powered 400DA is perfectly balanced, much better than the 340 I had with the same power.
Click to expand...
What does the 400 DA weigh. The 420 Ac dry is 27000 pounds.
Thanks
 
We have a 380 aft cabin with twin 454 you will burn 1 GPM at 6 knots. If we were to get a new big boat we would go with diesels. If you do less than 50 hours a year it is good boat.
Boat will do 22 knots but burn 55 GPH. Boat weight is 20,000 pounds dry we have it loaded and weight is 30,000 pounds.
 
I would say yes. My 44DB weighs in at 28,000lbs and is powered by Cummins QSC 500s at 478hp each and it is no speed demon. Loaded light at WOT I have seen 34mph....I cannot imagine 7.4 gas engines. Had a dock neighbor with a 370 Aft Cabin and I think it had 6.2s. To me, it was underpowered....A 2002 410 Dancer weighs in at 22,000lbs.

Bennett
 
cigars01 said:
What does the 400 DA weigh. The 420 Ac dry is 27000 pounds.
Thanks
Click to expand...

I am a svelte 23,000lbs in my 400DA.

I slip 2 slips away from an early 90's 45 Viking aft cabin powered by gas engines. Sure, it's a dog, but he's not running up and down the cost of Michigan every weekend. Seems to work famously for him and his family.
 
42 ft is ultimately too big and too heavy for 2 454 engines (they're 310 apiece). That thing will guzzle fuel like it's going out of style. In my opinion, anything 40 and up should be diesel.
 
For Lake Lanier, I dont think its under powered as we never really go that far, and none of the sea rays are over powered. It'll get you where you want to go except the biggest issue on the Lake (and Bennett can address this), is the height of the boat. You'll want to consider going North under Browns bridge and the other bridges on the North end of the lake, as this will limit where you can go. Also consider that the lake is going up 2' at normal pool, hence all the new bridges.

I'm a 2001 410 w CAT 3126's and we weighed in a 28,500 at the sea trial and I'm sure we weigh more like 30,000 filled with water fuel and all the other stuff that makes in onto the boat. My favorite cruising speed is at 2300 RPM going 20.6 kts or 23 mph burning 19.2 gal/hr and getting 1.07 NMpg or about 1.25 statute mpg. For cocktail speed, I use around 900-950 RPM going about 7.5 kts or 10 mph and sipping a little over 2 gals/hour and approaching 3 mpg.
 
Last edited:
bfernald0 said:
42 ft is ultimately too big and too heavy for 2 454 engines (they're 310 apiece). That thing will guzzle fuel like it's going out of style. In my opinion, anything 40 and up should be diesel.
Click to expand...
The engines are 340 hp as per the Searay brochure.
 
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