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GiorgioThai

2120 (1995) repowering

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After several years of happy cruising, it seems that the time has come to replace the old Yamaha F200 2 stroke.

Given the high price of the new Yamaha engines, I focused towards the new Suzuki series, especially towards the 4strokes DF175 and DF200A.
The seller suggested I choose the DF175, more reliable especially given the low quality of fuel sold in the area.
The price difference between the two engines is minimal (around US$ 700).

My uncertainty is on the (small) difference in power. I do not pretend to have a missile, but not even a rowing boat.

Some of you have already installed similar engines on a Robalo 2120 ?

Considering that my fishing trips mainly take place at more than 20 miles from the coast, I also asked if it is not appropriate to change the transom to install 2 outboards (for example 2 x DF90A). Someone has already done this modify ?

Thank You.

Giorgio
Phuket - Thailand

post-5435-0-49286500-1474910431_thumb.jpg

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No experience with the Suzuki's, but what is the difference between the 175 and 200 where fuel quality could be an issue? I would think as long as you are running at least a 10 micron fuel/water filter, what makes it past the filter should be fine. If both motors weigh the same, it is always nice to have the extra horsepower available when needed, especially on these heavy hulls.

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I installed a Suzuki 200 four stoke 1 year ago . The new online 4 cylinder because of the weight compared to a 6 cylinder . Top speed is around 39 fully loaded on flat waters , cruises good around 4600 rpm at 27 mph . Mpg at crushing is right at 3.0

 

Personally I think 175 is not enough for these boats . My Robalo is a 1997 2120 and they are heavy . Go with the 200 for the small difference in price

 

Best of luck . 75 hours so far with no issues at all .

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Hi Rooboy,
for now i'm still using the old Yammi 200 2strokes.

Last year i had a problem offshore and half boat went underwater.
The 2-stroke started regularly (it was almost submerged) and I could save the boat.
If I had a 4-stroke, with all the electronics they have, I probably would have gone to the bottom

I don't know exactly the size of the propeller, but i'm thinking is the standard 3 blades inox.

Anyway, with 2-3 persons on board, the cruising speed is 24 knots at 3800 RPM.
Top speed 38 Knots at 5000 RPM.
Fuel consumption about 40 liters per hour.

2018-05-12 10.53.25 (Large).jpg

Edited by GiorgioThai

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Care to share what happened offshore?

It could be a good learning experience for everyone on the board who goes offshore.

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Giorgio -

I missed your post back in September.  I think you can squeeze a little more performance out of that Yamaha.  At WOT, you should be able to see 5800-6000 rpms.  Anything less means the motor is straining a little.  

First thing to check is if it is sitting too low on the transom.  With it trimmed down neutral, the cavitation plate should be 1 to 1 1/2 inches above the bottom of the boat.  Any lower, you are dragging too much lower unit in the water and that is slowing you down.  If it is at the correct height and the compression on all cylinders is still good, time to start playing with props.  Every inch decrease in pitch should cause a 200 rpm increase.  If you have a dealer nearby that will let you test some different props, I would try two different sizes; one 2 inches less pitch and another 4 inches less pitch.  Compare speed vs rpms in 500 rpm increments to see which one gives you the best all-around performance.

I cannot tell from the picture, but if that is an OX66, those motors are darn near bullet proof.  Granted, going to a 4 stroke would be better fuel consumption and not as noisy, but that motor you currently have will run on just about any type of gasoline and are easily repaired if something does break.

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After a deep check of old engine ...
I have repowered and partially rebuilt the 2120 😁

- new engine Suzuki 200 4s 
- new steering system
- new batteries
- new fuel lines
- new electric system
- new bildge pumps
- new cockpit
- new gps-sounder
- new transducers
- new vhf
- new stereo
- new  gelcoat

Cruising speed 25 knots at 4.600 RPM, WOT 38 knots at 6.700 RPM
Pro:
fuel consumption about 40% less that the old Yamaha
less noise
easier start
more efficient battery charging

Con:
due to low transom, it's not possible some maintenance (like oil change) with the boat in the water
in case of rough sea, you have to work a lot with the throttle to avoid getting out of the plane
about 19.000 US$ less on the bank account 😢

 

Robalo 2120 fishing.jpg

2019-03-11 17.25.00.jpg

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Boat looks fantastic!  I had to go back to your first pictures when I first saw the black gelcoat job to be sure it was the same boat.  It does not look like a 24 year old boat at all!  If you did all that for $`19,000, you did very good.

One question, though.  Is that a mistake with the 6,700 rpms?  Other than the rpms, not bad on the speed.  I bet you could squeeze another 2 knots out of the boat playing with engine height and props. (On second thought, maybe not with the kicker motor still hanging back there).

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Hi 2-N-TOW,
the color of the gelcoat is dark blue, but, dependig of the sun, change from "eggplant" to light black. 

The RPM are right; after trying 3 types of propeller, the dealer has installed one 15-3/4x21 SS and run very well.

i'm have plan to remove the kicker motor, because now the upper part of the stern is dangerously close to the water.

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"i'm have plan to remove the kicker motor"

Too late 😄

Some days ago, during a strong tropical storm, one of two bildge pumps has stopped and another one was off.
The rain start to go inside the boat and the old rear scupper drains allow to the sea water to increase the level in the bildge.

Luckily the boat don't sunk ...

Now the Robalo still at the dry in the shipyard.
I have to replace/check the bidge pumps, seal the aft 
hatch, replace the scupper drains, partially rebuild the electric system in the battery compartment and, obviously, remove the Yammy 15 (50 kg. less on the transom).

I'm thinking also to install an engine bracket and raise the transom. 

 
 

2019-04-29 10.53.09.jpg

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Did you ever get lucky!

21 ft is the bare minimum for bracketing based on what I found when I did mine.  If you add a bracket, you will need to shift a considerable amount of weight forward to offset that 4 stroke motor hanging 30 inches further back behind the transom.  If your batteries are at the transom, they have to be moved to the console.  You may also need to put some weight up in the bow to help get the center of gravity  back where it was designed to be.  If you don't have trim tabs, definitely add them if the bracket is added...makes all the difference in the world for getting on plane and running in rough water.

One big positive once the boat is set up with the bracket....it will handle like a bigger boat and be much  more enjoyable in bumpy water.  I was pleasantly surprised in what an additional 30 inches in overall boat length did to my boat.

What are your plans for enclosing the transom?  I incorporated 2 fish boxes across the back of the boat extending 12 inches forward of the original transom.  The box structure also added some strength to the transom along with the 2 knee braces I installed to extend the stringers up higher.  Look at my rebuild thread 

It shows what I did rebuilding the 2160.

Let me know if you have any questions about it.

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