New Suzuki 90 seems way too loud

HuntnFish925 · Posted: Wed May 14, 2025 6:44 pm Post subject: New Suzuki 90 seems way too loud

Hello all,

Long time lurker, and finally made an account. We recently re-powered our 2002 22 Cruiser with a 2023 Suzuki 90DFA. It has a 15 pitch aluminum 3 blade prop. We love the motor. Starts with barely a turn of the key, has plenty of power, and looks great on the boat. Previously, the boat was outfit with twin Yamaha 40hp.

We have one issue. The noise! The noise increase over twin 40hp is incredible. The motor seems SO much louder. It was even more so evident on our last trip. We went out fishing in some pretty rough seas. On our way back to port, we could only motor at about 9-12 mph. This put the motor right around 3200-3900 rpm. The harmonic noise and motor noise was unbearable. It seems like it turned the whole boat into an instrument and the vibration thought the entire boat was very loud. 2 people on the boat used kleenex in their ears as ear plugs and sat and covered their ears with their hands as it was almost unbearable. The trip back to port was about an hour. The noise from the boat was horrible.

So Im wondering if this is normal? Mind you, I used a Suzuki dealer that I was NOT happy with their install. They did a horrible job. Which I didnt know until after the purchase and install obviously. Im wondering if this was something that was messed up during install? Our twin 40's never made this much noise, or caused such a loud harmonic noise though the whole boat like this.

I know a lot of people have this motor. I love the motor. Just want to try and figure out a way to make trips, especially in the 3000-4000 rpm range, at least tolerable.

colbysmith · Posted: Wed May 14, 2025 9:27 pm Post subject:

Any chance you have a damaged prop or drive shaft?

thataway · Posted: Wed May 14, 2025 9:50 pm Post subject:

That is not "normal"--we have a 140 Suzuki on my 18' Caracal Cat, and it is a quiet engine as they go. I am not sure what could cause that issue. However some resonate frequency is possible. Did you check out the transom? Two 40's and to a single, would have more holes in the transom.

HuntnFish925 · Posted: Wed May 14, 2025 11:41 pm Post subject:

Definitely not a damaged prop or shaft. The prop is still brand new looking, not a single scratch. The motor has only been in fresh water a few times and the ocean a few times. It has been like this since we got the new motor.

The holes in the transom were "filled" by the shop. They had wooden dowels plugged into them, and new glass was put over the back of the transom. You cant even tell there were twins on there before from the outside.

Im just worried it was something about the way the outboard was actually mounted. They completely screwed up all my wiring that wasn't outboard related (long story). So it wouldn't surprise me if they did something wrong on the mounting.

The motor makes EVERY panel on the boat vibrate, not like a violent shake, but a high frequency resonance. Especially between 2900-4000 RPM.

tsturm · Posted: Wed May 14, 2025 11:56 pm Post subject:

Joefairbanks · Posted: Thu May 15, 2025 11:26 am Post subject:

Just throwing this out there-
Have you checked the bolts going through the transom that they used to bolt the new motor on? Check for tightness, as I can imagine a loose bolt or two would make vibrations like crazy.
Maybe check while you're there to see if they sealed anything when they redrilled for the new motor.
Just a suggestion...

kcohen4 · Posted: Thu May 15, 2025 12:52 pm Post subject: Noise

Years ago I had same problem. I was trying different props with different pitch. I don't remember exactly which one caused the problem but when I changed the pitch of the prop the noise went back to normal

Xtraplus18 · Posted: Thu May 15, 2025 3:27 pm Post subject:

My 2017 115HP Suzuki make little noise underway. I would check the prop or maybe the shaft internally may be slightly bent. Manufacturing defect?

These are very good engines. I see more and more in my area.

If you are in Oregon John from Sportscraft Marine or Blackhawk Marine might be able to help out.

BigSwede · Posted: Thu May 15, 2025 10:51 pm Post subject:

Even a 2-stroke wouldn't be that loud... can't be normal.

HuntnFish925 · Posted: Sat May 17, 2025 3:21 pm Post subject:

Joefairbanks · Posted: Sat May 17, 2025 4:14 pm Post subject:

Not having the top of the mount resting on top of the transom is fairly normal. The height of motor can be adjusted as needed, up or down. There should be 4 bolts mounting it to your transom, and nothing else. Most people use some type of marine sealant/light adhesive between the bracket and the transom. Also, the bolts should be sealed as well.
At least that is what I have seen. I’m sure someone with more experience and knowledge than I will also chime in here.

Tug · Posted: Sat May 17, 2025 4:44 pm Post subject:

I just did a quick search ,one cause may be that the impellor housing has corroded or cracked. This may cause a knocking noise as the impellor spins, replacing the impellor housing should fix it. ??