90 HP 4 cycle performance

[Rhody]

Is anyone runing a 18' or 20' seacraft with a F90,Suzuki DF90 or a honda 90HPEFI? I am wondering if they can push a seacraft at a reasonable rate. These motors are not too heavy (348-370#)so I thought they might be adequate to the task.

[fdheld34]

Fr. Frank runs a 90 Opti on his Seafari...hopefully he will chime in!!!
FRED

[ehmarks75]

I run a 2001 115 hp Mercury Saltwater 4 Stroke on a 2001 20' Master Angler. It runs well, reaching 41 mph on a glass calm bay, and fuel consumption is very good but the hole shot is only fair in my view. A 90 hp might be a little insufficent on a 20' hull.

[Michael Vezzosi]

Rhody, my brother has had a 1986 18 since 98 or so. Started out with possibly the original OMC 112. Repowered with a rebuilt OMC 150. This winter he almost bought a used 150 to 175. 25 inch transom, but I'm thinking he'd have to stay two stroke.

I've got a 99 175 on my 20 MA. And an F60 on each 15 Whaler. I wouldn't want a 4S 90 on an SC 18 or a 20, unless it was a Fathers Day Gift. I do fish a lot from a 18'6" Mako/Kenner/F? bay boat with a 2003 Suzuki 90 4S, but there are times she wishes she had a 115 or 140 4S. Same weight, I believe. Just my $ .02. Part II.

[Fr. Frank]

Not to disdain Part II's position, but 90hp is certainly adequate, and demonstrably economical. You just can't go so fast you howl at the moon while flying "balls to the 'wall" at WOT.

1st, I run a 375 lb Mercury 90hp Optimax on my '72 Seafari. I do not have trim tabs. My hole shot is under 5 seconds, cruise speed is 25-26 mph, and WOT speed is about 33-34 mph with an average load. I get 5.1 mpg at cruise, and 3.2 mpg at WOT.

Just for the record, when I had the XR4 on the back, which produced an actual 190hp, my hole shot was about 3.5 seconds, I cruised at the same 25-26 mph, and my WOT speed was just over 50mph, lightly loaded. I got 3.5 mpg at cruise, 2.7 mpg at 35 mph, and 1.5 mpg at WOT. (I always ran WOT for 2-3 minutes every time I went out to minimize carbon build-up from using a straight 50-1 pre-mix, as I deliberately disabled the factory automatic oiling).

There are very few occasions where I desire to run faster than cruise. I really enjoy the economy and reduced maintenance of the Optimax. I used to run out to the Florida Middle Grounds with the XR4, and had to carry an extra 30 gallons of fuel on the deck (one 18 gallon portable, and two 6 gallon portables) to make the round-trip, depending on where I launched, as my factory tank was only 29 gallons. (Tip: burn from portable tanks first)

With the new motor, I also got a new fuel tank. My new tank is 28 gallons usable, but even so, I carry only the two extra 6 gallon tanks launching from Hudson. The Middle Grounds are 85 miles from Crystal River, and 68 miles from Hudson or Clearwater. I get there in about the same amount of time, but it costs me $60 less. That's enough during the summer for 3 rounds of golf (with cart) at any of my 5 favorite golf courses.

Ya gotta put things in perspective.

[Rhody]

"Fathers Day Gift" thats a good one. I guess adequate is different for each person.

Fr. Frank how do you think one of the new 4S 90's would do on your rig? If I recall on one of your posts you estimated your 90 Opti put out 100 or more HP. Mercs are often rumored to produce well above their nominal HP.Along that same line the new Honda 90efi uses the motor from the Honda Fit.Same displacement(1497cc),same bore and stroke.Compression not sure. It rates 117hp @6600rpm. 106#torque @4800rpm.Of course the outboard is rated at the prop shaft which might be the difference.

[Michael Vezzosi]

Padre, even though my brother inherited my fathers Jersey Speed Skiff, when fishing alone, he does admittedly run WOT everywhere. I believe he knows he cannot afford to repower, but if it blows his family will not be happy without "Dad's SeaCraft". I guess its a theory.?. And I guess 90 horses are ample. Part II.

In his defense, I'm the JA with the 1999 175 with 140 hours. Two years ago, I went to leave the sand bar with 12 other fireman on scene. She started perfectly, then farted and stalled. Of course the one from Jersey says "It's starving for Garage Air"! Nice.

[eggsuckindog]

Personally I don't think its nearly enough, you usually have to go up in HP to equal a 2S. Most 20's that go Zuke use the 140 and alot including me go all the way to 200. I just don't think it will work and could become very expensive trial. IMHO they need 140/150 to run correctly, I didn't say run, just correctly. I don't need all 200 but I damn sure don't want to send somebody to the bow to get on plane either. The boats Max HP was 150 then 175 - 90 is getting close to half that and 4 S's ain't the fastest in the arena anyway. In a more exotic description, the boat is designed to get up on the deeper deadrise center sections of the hull, to do that you need HP. The boat would just slog through and you would negate the advantage of the hull. If its on a Carolina Skiff with no deadrise fine but not a deep vee SC.

[nos3665]

1st, I run a 375 lb Mercury 90hp Optimax on my '72 Seafari. I do not have trim tabs. My hole shot is under 5 seconds, cruise speed is 25-26 mph, and WOT speed is about 33-34 mph with an average load. I get 5.1 mpg at cruise, and 3.2 mpg at WOT.

Just a Question or or 2 what size/ Pitch Prop,@ what RPM does your engine make that 90 HP?

How far from the Hull is the Lower plate on drive in height?
I have a terrible bad back and have put off repairing the transom on the 74 20' I picked up last spring but today I did pull the cover and back her up to the shop and plan to start the transom this week.
I have to use what I got which is a 1989 90 hp Force at this time.
it makes 90 hp @ 5000 RPM and weighs 304 lbs and prop sizes are Limited I hear for that engine 13.5 and 15 pitch thru 21
I may have a 17 on now I will pull and check it.
This will be my first transom job so I am not looking forward to it. feel free to jump in on advice thanks for being here Guys. BTW the way the Seas run here on a avg day running mid-range or less is fine for me.

[Fr. Frank]

what size/ Pitch Prop,@ what RPM does your engine make that 90 HP?
How far from the Hull is the Lower plate on drive in height?

I have to use ...a 1989 90 hp Force at this time.
it makes 90 hp @ 5000 RPM and weighs 304 lbs and prop sizes are Limited I hear for that engine 13.5 and 15 pitch thru 21
I may have a 17 on now I will pull and check it.

First of all, I have a 2.33:1 gear ratio, and I run a 4-blade 19p TrophyPlus, or a 3-blade 21p Michigan SST (30 years old). Most of the time I run the 3 blade. The figures I gave were with the 21p.
I make that max power at 5450 rpms on the hydro-dyno.
My cavitation plate is about 1.5 inches above the keel, and I have a hydro-shield mounted to the skeg below the prop.