Thread: Optimax vs 4 stroke-Merc

That Is A Good Question My Boat Is Rated For 90hp But Is That A Conv. 2 Stroke Or Will It Handle A 4 Stroke?

I guess the question would be is the HP rating for a boat bases on weight of the motor or thrust of the motor? Which is the transom tested for? CF

It depends. Strictly on fuel, you'll probably be better off with the Opti, but the 4 stroke will be close. Opti will be faster on the top and stronger out of the hole. It will be relatively quiet at idle (compared to a 2 stroke). The 4 stroke will excel at idle if you troll, both for being quiet and on cost of operation. In the mid range fuel economy will switch back and forth with the 4 stroke winning some rpms and the Opti others. The 4 stroke will win out on day to day service cost. You can change your own oil, plugs, L/U and water pump. With the Opti, personally, I'd only run Merc Opti oil and their brand of fuel additive at a premium price due to my personal belief of running them as clean as can be. Due to that, for me, the operating costs would be higher with the Opti.

For me, I choose the 4 stroke in the mid range, but would consider going to Opti once I topped the 150 mark because I'd obvioulsy be looking for a lot more speed if the hull was rated that high. In the mid and low HPs, I prefer the operating characteristics of the 4 strokes.

Still, at times, I'd like to have the 3 to 5 mph of top end the addtional 2 strokes is costing me.

Wannabe...

Originally Posted by Wannabe...

It depends. Strictly on fuel, you'll probably be better off with the Opti, but the 4 stroke will be close. Opti will be faster on the top and stronger out of the hole. It will be relatively quiet at idle (compared to a 2 stroke). The 4 stroke will excel at idle if you troll, both for being quiet and on cost of operation. In the mid range fuel economy will switch back and forth with the 4 stroke winning some rpms and the Opti others. The 4 stroke will win out on day to day service cost. You can change your own oil, plugs, L/U and water pump. With the Opti, personally, I'd only run Merc Opti oil and their brand of fuel additive at a premium price due to my personal belief of running them as clean as can be. Due to that, for me, the operating costs would be higher with the Opti.

For me, I choose the 4 stroke in the mid range, but would consider going to Opti once I topped the 150 mark because I'd obvioulsy be looking for a lot more speed if the hull was rated that high. In the mid and low HPs, I prefer the operating characteristics of the 4 strokes.

Still, at times, I'd like to have the 3 to 5 mph of top end the addtional 2 strokes is costing me.

Wannabe...

The Optimax IS a two stroke motor,...only it is fuel injected and not a carbed
two stroke. Still,it should be lighter than a four stroke motor and it will have more torque than a four stroke since it is firing every revolution whereas a four stroke only fires every other revolution. Stick with the Optimax if weight
is a concern to you.

I love my four stroke. I have a 60 on a 17'7 war eagle. Great hole shot and fuel economy is great. Very quite. They say the first thing to go out on the four strokes is the starter b/c people forget they are running and turn the key again.

Mistyped, meant compared to a 4 stroke.

Wannabe...

Stop the presses.....anyone heard of the new Yamaha Vmax SHO 4 strokes? Being rolled out soon and is "34 pounds lighter than the standard Vmax". I take that to mean 34 pounds lighter than the EFI 2 stroke, not the DFI 2 stroke.

Not only that, but the review basically said the SHO kicked all the other engines to the curb.

There's also mention of a 70 hp version, so I'm sure there will be a 115 version pretty soon as well.

No mention of the price, but I'm sure it'll probably be 8 or 9 dollars higher than the Vmax. HPDI or 4 stroke

BassFan.com

Wannabe...

Maximum Rated Horsepower
Horsepower Ratings and Questions Related to Them
All boats manufactured and sold by Boston Whaler have been rated for a maximum horsepower. Some owners have chosen to install engines that exceed these ratings, and thereby raised several questions: How is the rated maximum power determined? Is powering above the rated maximum legal? Will dealers or service shops install an engine that exceeds the maximum rated horsepower for a boat? Can insurance coverage be purchased for boats powered above their rating?

How is the maximum rated power determined?
In response to a mandate from Congress contained in the Federal Safe Boating Act of 1972 (FSBA), the United States Coast Guard issued regulations covering small outboard boats and the maximum rated horsepower for them. The regulations bind the manufacturer to provide a capacity plate that shows the maximum rated horsepower for each hull.

The applicable regulations can be found in 33CFR183.53 My interpretation of those regulations is that the manufacturer must state the horsepower as no more than that computed under the formula, except, if the manufacturer conducts the performance testing procedure, the results of that testing can be used (with some qualifiers). However, the manufacturer is apparently free to state a lower rating if desired, and sometimes does. Note that the regulations only require ratings for monohull boats under 20-feet in length, but Boston Whaler has historically provided a rating plate for its boats longer than 20-feet as well.

The formula provided in the regulations reduces to:

(2 X L X W) -90 = rated horsepower

Where:

L=boat length
W=transom width; if the boat does not have a full transom,
the transom width is the broadest beam in the
aftermost quarter length of the boat.

The rated horsepower may be rounded up to the nearest "5".
Here is an example of how the rating formula works in practice, applied to an older Boston Whaler boat, the V-20 model:

Boston Whaler V-20
Length = 19' 10"
Width = 7' 5"

Thus:

(19.83 x 7.42 x 2) - 90 = 204.15
Rounding up = 205 maximum rated horsepower
In the case of the V-20/Outrage 20, from 1978 through 1985 Whaler chose to give it a maximum rating of 180-HP instead of 205-HP. Affixing rating labels which are lower than the rating permitted under the formula is common.

Is powering above the rated maximum legal?
The United States Coast Guard has an opinion on this frequently asked question, and their answer from their website is reproduced below:

Can I use a bigger motor on my boat than what it's rated for?

It is not a violation of Coast Guard regulations to install or use an engine larger than specified on the capacity label, but there may be state regulations prohibiting it, and restrictions from your own insurance company regarding this.

There are no Coast Guard regulations against exceeding the safe loading capacity, however, there may be State regulations or restrictions from your insurance company which prohibit this. There is a Coast Guard regulation that gives Coast Guard Boarding Officers the power to terminate the use of a boat (send it back to shore) if, in the judgment of the Boarding Officer, the boat is overloaded. There is no fine for this, unless the operator refuses the Boarding Officer's order. We certainly hope that you will abide by the rating, as overloading may lead to capsizing or swamping of the boat

Originally Posted by Wannabe...

Stop the presses.....anyone heard of the new Yamaha Vmax SHO 4 strokes? Being rolled out soon and is "34 pounds lighter than the standard Vmax". I take that to mean 34 pounds lighter than the EFI 2 stroke, not the DFI 2 stroke.

Not only that, but the review basically said the SHO kicked all the other engines to the curb.

There's also mention of a 70 hp version, so I'm sure there will be a 115 version pretty soon as well.

No mention of the price, but I'm sure it'll probably be 8 or 9 dollars higher than the Vmax. HPDI or 4 stroke

BassFan.com

Wannabe...

I also take it to mean that the VMAX HPDI two stroke motors are gone and
have been replaced by the VMAX SHO 4 stroke. Am I correct? I read the same article and that is the impression I am getting.

no, the HPDI will be back for 2010