700HP on a Marlin

Jestimator2

Jestimator2

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Hello all! I have a line on two brand new 350HP Yamahas for a good price, has anyone put twin 350’s on a 300 Marlin? Mine is a 2002 and says it’s rated for up to 600HP. Thanks!
 
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And that you'll be well outside your HP rating in the event you are involved in boating accident,,, it'll all be on you.
 
There is a reason why the 350s are a 'good' deal. Do your research.
That said, in addition to potential insurance issues and liabilities, there may be issues with the extra strain put on the transom
 
V8, or the new V6? Talk to your insurance company, and get it in writing that your coverage will not be affected.
Yamaha did not introduce a 350 until 2007, but your boat probably had max horsepower for the time. If weight and performance are not dramatically increased, they should give you the waiver. It is not an unusual thing for people repowering.
 
Too much power and weight if you ask me. F350s scare me from a reliability standpoint.
 
glacierbaze said:
V8, or the new V6? Talk to your insurance company, and get it in writing that your coverage will not be affected.
Yamaha did not introduce a 350 until 2007, but your boat probably had max horsepower for the time. If weight and performance are not dramatically increased, they should give you the waiver. It is not an unusual thing for people repowering.
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His first comment mentions "two brand new 350HP Yamahas", of which I don't imagine that they're brand new units from the mid 2000's.
 
Why the need for 350's? Per the Grady White website, a brand new 300 Marlin with twin F350's on it will do a top speed of 55 mph, and even with twin F300's, the boat still does 50 mph. I don't know about you, but 50-55 mph on the water is considerably faster than I ever need to go and it seems like it's maybe more for bragging rights than anything else at that point. I imagine with twin 250's on the boat that you should still be able to go between 40-45 mph at top speed, which is more than fast enough for me. Perhaps Fishtales will give the fuel/performance numbers on his boat...
 
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Those new v6 350’s are powerful and light weight! Think I’d like to hang one on the back of my 208. Just for fun.
 
Jestimator2 said:
Thanks for all the input, just got this off the the Grady owners resource page
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The V6 just came out this year, didn’t it? The link you were reading may have applied to the V8’s.
 
Mustang65fbk said:
Why the need for 350's? Per the Grady White website, a brand new 300 Marlin with twin F350's on it will do a top speed of 55 mph, and even with twin F300's, the boat still does 50 mph. I don't know about you, but 50-55 mph on the water is considerably faster than I ever need to go and it seems like it's maybe more for bragging rights than anything else at that point. I imagine with twin 250's on the boat that you should still be able to go between 40-45 mph at top speed, which is more than fast enough for me. Perhaps Fishtales will give the fuel/performance numbers on his boat...
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The newer boats are built for 700HP. Earlier models were 500 or 600HP. Mine is 600HP and I have F250s. With light fuel and crew, you can hit 50MPH is relatively flat conditions with a burn of 1.0 -1.21 GPH as I recall. I rarely mash it these days. Can cruise comfortably 44-45 MPH with 1.3 or so. I don't care about fuel burn to be honest and never paid much attention nor tracked it closely. On a 500HP boat, the 700HP seems excessive and that was my input to the OP. If I were buying new, then twin 300s or 350s would be fine with me, I'd prob never mash it often, so it's all reserve if needed. I'd be buying a stock boat late in the season to get my best deal, so I'd take whatever was on the transom. If I ordered, 300s would be plenty for me.
 
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Fishtales said:
The newer boats are built for 700HP. Earlier models were 500 or 600HP. Mine is 600HP and I have F250s. With light fuel and crew, you can hit 50MPH is relatively flat conditions with a burn of 1.0 -1.21 GPH as I recall. I rarely mash it these days. Can cruise comfortably 44-45 MPH with 1.3 or so. I don't care about fuel burn to be honest and never paid much attention nor tracked it closely. On a 500HP boat, the 700HP seems excessive and that was my input to the OP. If I were buying new, then twin 300s or 350s would be fine with me, I'd prob never mash it often, so it's all reserve if needed. I'd be buying a stock boat late in the season to get my best deal, so I'd take whatever was on the transom. If I ordered, 300s would be plenty for me.
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My "Why the need for 350's?" question was mostly aimed towards the OP, because as I'm sure you're well aware and especially on the older models of the boats, they have a considerably lighter dry weight to them. The 2002 GW 300 Marlin that the OP has comes with a dry weight of 7,000 lbs as opposed to a brand new one which has a dry weight of 8,221 lbs... so a difference of almost 1,225 lbs. That being said, even your 2006 claims to have a dry weight of the heavier 8,221 lbs per the brochure. Of which, if your figures listed above are accurate, the top speed of 50 mph with a light crew and fuel would make it seem like the twin 250's are very much up to the challenge. Unless one was heavily loaded down every single time they went out and for some reason needed a boat that would go over 50 mph. I imagine your boat even moderately loaded down still hits a top speed of around 45 mph, though? And yes I agree, the 700 hp seems quite excessive.
 
"With light fuel and crew, you can hit 50MPH is relatively flat conditions with a burn of 1.0 -1.21 GPH as I recall........"

If I were getting 40-50 MPG, I would be happy as a clam.
 
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