Retracting trim pistons (Yamaha)

[Pat Hurley]

I noticed that the trim pistons/rods on my Yamaha motors (30 Marlin) are underwater when the motors are up so I flip the engine supports and retract the pistons back into the cylinders to prevent corrosion from damaging the seals. However when I do that the lowers dip back a little deeper beyond the ablative line that was painted on them when I purchased the boat. Guess I'm gonna have to get it pulled to strike a new line to prevent corroding the lowers. Are there other Gradys that have this issue where the trim pistons are underwater or is it a Yamaha THING ?

 

[SkunkBoat]

My old OX66s sat with lower units 5" deep and trim at water line and the rods pitted. I did not know about the "lower onto the supports,then lower pistons so they pit at the top where it does not matter" thing.

it is genius.

my new zukes sit with trim above water and lower units high & dry
Its not a weigh thing because the zukes weigh more than the ox66s

 

[Pat Hurley]

That (Zukes) would be a serious consideration if repowering down the road. Has anyone repowered a Marlin with Suzuki motors and what was your experience ? Lowers and trim up and out of the water ?

thanks

Pat

 

[Kizuna]

Hi Pat,

I repowered with DF300s. Trim system sits out of the water, but the front tips of the lowers are still dipped in the water with full trim up. I'd say a couple inches, probably 3" with full tanks of gas.

 

[Pat Hurley]

.... thank you Kizuna !!

 

[seasick]

What has changed? If nothing but the water line has risen, you may have an issue with added weight. That can be gear or to some extent paint buildup but it could also be water intrusion.

 

[Pat Hurley]

What has changed? If nothing but the water line has risen, you may have an issue with added weight. That can be gear or to some extent paint buildup but it could also be water intrusion.

Nothing has changed other then when you put the stops down and then lower the tabs there is enough play to allow the motors to sit lower. The previous owner painted the lowers without consideration of retracting the pistons thus the need to re strike the line

 

[seasick]

I think I understand.
The motor doesn't sit lower since the weight is the same but the lower unit is at a different angle because the motor drops a bit to sit on the stop.
My question had to do with the fact that the trim cylinders were completely submerged. That suggests that the hull got heavier and/or that the motor is mounted too low. Where does the antiventilation plate sit when the motor is trimmed straight down?

 

[Pat Hurley]

I think I understand.
The motor doesn't sit lower since the weight is the same but the lower unit is at a different angle because the motor drops a bit to sit on the stop.
My question had to do with the fact that the trim cylinders were completely submerged. That suggests that the hull got heavier and/or that the motor is mounted too low. Where does the antiventilation plate sit when the motor is trimmed straight down?

Cavitation plate level is good. I’ve been told this is an inherent design issue with the Marlin and the Grady Cat in conjunction with the Yamaha’s. A dock neighbor of mine pointed this out to me. Kizuna stated that his DF Suzuki 300’s trim units are located up and out of the water

 

[seasick]

There is at least one Marlin, maybe two at my club. I will try to take a look at how the boat sits in the water.

 

[Pat Hurley]

Hi Pat,

I repowered with DF300s. Trim system sits out of the water, but the front tips of the lowers are still dipped in the water with full trim up. I'd say a couple inches, probably 3" with full tanks of gas.

... how does she perform with those 300’s. Cruise rpm, gph, mpg etc

many thanks

 

[Kizuna]

... how does she perform with those 300’s. Cruise rpm, gph, mpg etc

many thanks

The 300s are a big step up from the 225s I had before. Lots or torque and the larger prop makes docking the boat easier. No need for a bow thruster. The drive by wire took a little getting used to, but in a day or two you'll forget what the cable ever felt like. I also like that trim is measured by %, so it's more accurate than the Yamaha bars/blocks. Maybe they've updated since.

As far as performance, I typically cruise between 4,000-4200 RPMs which puts me around 30 MPH, and getting ~1.4-1.6 miles per gallon. Obviously conditions will have impacts, but I would say this is at least close to my average. If I slow it down a bit, 3800-3900 and 28ish MPH I'll see 1.7-1.9 mpg. Cruizing speeds generally burns around 19-20 gph. These numbers are also after I get her "settled in". Everything is higher getting up on plane, but with in a minute of cruising I can get the trim, rpms, tabs if needed, dialed in. In the right conditions I've see as good as 31-32 MPH with 1.7 MPG; this I was also with a light load.

My props allow the engines to top out at 5700-5800 RPMs with a top speed around 44 MPH, sometimes I might get a little more if I'm light.

My average load is 3-4 Kids + 4 or 5 Adults, 50% fuel, water tank is topped off frequently, and the boat is loaded with plenty of fishing gear, drinks, ice, etc.

 

[seasick]

I took a look at that Marlin at my club. It is a 2002 with F225s. With both tanks full, the top of the trim cylinders are just about at the water line with one person on the deck. With less gas, the rods would not be under water but could easily get splashed at the dock by wakes. If the person moves aft to look at the motors, about a half inch of the rod is below the water line.
I also noticed that about 3 or 4 inches of the lower unit is below the water with the motors tilted up (not on the safety rest)

 

[Kizuna]

Pat, I won't be able to get to my boat for another week or so (kid commitments) but I'll try and remember to get some picks of how my boat is sitting now. Currently nearly full tanks since the last time out I toped them off to recalibrate the gauges.

 

[drbatts]

Not an exact comparison but the trim system on my 305(same hull) with f300's is completely out of the water. My lower units sit a couple inches deep in the water, which was the same with my previous 265.

 

[Kizuna]

Hi Pat, so it seems I’ve been mistaken, and my trim tabs do sit in the water. At least with full tanks of gas. I’ll inspect again when the boat is lighter.

 

[Pat Hurley]

Kizuna,

I can see from the picture a little bit of your piston is in contact with the water. Mine were a couple inches under so they need to be retracted to prevent corrosion which subsequently would ruin the seals when running them in and out. The previous owner had the lower units painted to the water line without consideration of putting the safety stops down and retracting those pistons. When you put the stops down the lower units dip in a little further in thus I had to re strike the ablative (Trilux 33)paint line to prevent corrosion there also. We pulled the boat to set the correct line and took advantage of the haul out and did an oil change on the motors and lowers. Prior to launch this spring we had the trim seals replaced on my port motor and I suspect this was the culprit.

 

[Kizuna]

Pat,

Slightly off topic, but since you asked earlier in this thread; I took some pics of the kind of numbers I get with the Zukes. I had 5 adults and 5 kids aboard with over 230 gallons of gas. In the first pic running @ 4156 RPM, I was going 31.7 MPH, getting 1.53 Nautical MPG, and burning 17.96 gallons per hour. In the second pic I was going 33 MPH @4250 RPM, 1.49 NMPH and burning 19.15 GPH. The conditions were calm and this in the bay, not off shore.

 

[Pat Hurley]

.... that’s some awesome numbers there. Much improvement over the 225’s or 250’s. What size props etc ?

 

[Kizuna]

.... that’s some awesome numbers there. Much improvement over the 225’s or 250’s. What size props etc ?

I had 225's so yes a huge improvement. With them, I would cruise at 4400-4600 RPMs, and would be going slower with higher fuel burn. I'm currently running 3/16/8.5 props.