Air to the Engine

[steelhorse454]

To the experts...

I have a single engine 2023 SVHO and just replaced my air filter with the RIVA K&N type just for the hell of it hoping to gain 100 rpms or so. I noticed that the opening to the stock air box cover is within a couple of inches to the vertical fiberglass at the rear seat. Inside the boat, facing the back, small section of fiberglass under the seat to the right of the Fire extinguisher port. ( Sorry no pics )
Question, would drilling say a 2" hole through the fiberglass, and installing a perforated round cover plate of some sort, give any advantage to getting more air into the engine compartment? Advantage meaning more engine performance. I realize the risk is taking a huge wave and water getting into the engine area, but I truly don't see this happening the way we boat.
Thanks in Advance.
Jim

 

[FSH 210 Sport]

To the experts...

I have a single engine 2023 SVHO and just replaced my air filter with the RIVA K&N type just for the hell of it hoping to gain 100 rpms or so. I noticed that the opening to the stock air box cover is within a couple of inches to the vertical fiberglass at the rear seat. Inside the boat, facing the back, small section of fiberglass under the seat to the right of the Fire extinguisher port. ( Sorry no pics )
Question, would drilling say a 2" hole through the fiberglass, and installing a perforated round cover plate of some sort, give any advantage to getting more air into the engine compartment? Advantage meaning more engine performance. I realize the risk is taking a huge wave and water getting into the engine area, but I truly don't see this happening the way we boat.
Thanks in Advance.
Jim

That would not be a good idea. Someone else here was looking at doing that a while back and was advised not do that for the same reason, loss of sea worthiness. If you really want to see if it will make a difference, prop the engine hatch open a couple of inches and then go run the boat and see if you pick up any rpm at wide open throttle, if you think you have, close the engine hatch completely and see if the rpm drops.

If your engine is reaching normal max rpm then there is nothing to be done anyway. What are your maximum rpms?

Another thing you can try is turn on the bilge blower while cruising along at wide open throttle and see if you pick up any rpm that way.

 

[zipper]

There is a 4" hole in the back of the engine compartment for the blower exhaust. It is behind the seat back on the swim platform. Blower/ intake is on one side, the hole/exhaust is on the other. Twin engine boats have two blowers/intakes and two holes/exhausts behind the swim platform seat backs. Maybe add another hole there. Combustion air comes in thru that/those holes when the blower is off. Pics of your design please.

 

[steelhorse454]

That would not be a good idea. Someone else here was looking at doing that a while back and was advised not do that for the same reason, loss of sea worthiness. If you really want to see if it will make a difference, prop the engine hatch open a couple of inches and then go run the boat and see if you pick up any rpm at wide open throttle, if you think you have, close the engine hatch completely and see if the rpm drops.

If your engine is reaching normal max rpm then there is nothing to be done anyway. What are your maximum rpms?

Another thing you can try is turn on the bilge blower while cruising along at wide open throttle and see if you pick up any rpm that way.

Thanks for the response and understood. Not exactly sure on the RPMS but around 7,700 I would guess.

 

[steelhorse454]

There is a 4" hole in the back of the engine compartment for the blower exhaust. It is behind the seat back on the swim platform. Blower/ intake is on one side, the hole/exhaust is on the other. Twin engine boats have two blowers/intakes and two holes/exhausts behind the swim platform seat backs. Maybe add another hole there. Combustion air comes in thru that/those holes when the blower is off. Pics of your design please.

Thanks. I'll check that out.

 

[FSH 210 Sport]

Thanks for the response and understood. Not exactly sure on the RPMS but around 7,700 I would guess.

According to willm in this thread. 2023 255xd Maptuner X tunes It appears that the ECU’s for the 1.8’s limit rpm to 7500-7700, so if you’re getting 7700 then your engine is running at rated rpm and there would be nothing to gain.

Could you benefit from cooler combustion air into the engine bay? Probably. I’d check into what @zipper said, you may find that there are already two induction air holes behind one of the back rests for the swim step. The cooler the air coming in, the lower the density altitude and the more fuel the ecu will deliver to the engine. I have confirmed this on hot days by turning on the bilge blowers so that more outside air is drawn into the engine bay…but thats in my situation where I am not topped out on rpm.

The RIVA air filter you put in will probably help, you could test it by making back to back speed runs with the stock air filer in place then swap it for the RIVA.

 

[steelhorse454]

Do those back rests on the swim platform just slide up on a track to remove ?

 

[zipper]

Do those back rests on the swim platform just slide up on a track to remove ?

The fasteners should be visible from the engine compartment. Find the blower/hose/hole, the fasteners should be around it. Same on the other side with the hole cutout. There is a gap between the seat back and the fiberglass to allow air flow. Air is pulled from the bottom of the seat back, up and into the engine compartment. With the engine warmed up, run the blower the put your hand under one of the two seat backs, you will feel the heat being exhausted from behind the back rest. You can see the hole at the back of the engine compartment. This seat is popular on a cool day, as it is known to warm up its occupant. But be aware of CO present while engine is running.

 

[steelhorse454]

Thanks Zipper. Good Information.

 

[JETSKIJIMMY]

To the experts...

I have a single engine 2023 SVHO and just replaced my air filter with the RIVA K&N type just for the hell of it hoping to gain 100 rpms or so. I noticed that the opening to the stock air box cover is within a couple of inches to the vertical fiberglass at the rear seat. Inside the boat, facing the back, small section of fiberglass under the seat to the right of the Fire extinguisher port. ( Sorry no pics )
Question, would drilling say a 2" hole through the fiberglass, and installing a perforated round cover plate of some sort, give any advantage to getting more air into the engine compartment? Advantage meaning more engine performance. I realize the risk is taking a huge wave and water getting into the engine area, but I truly don't see this happening the way we boat.
Thanks in Advance.
Jim

RIVA Yamaha 2018+ SVHO Intake Manifold Upgrade Kit

RIVA Racing's Yamaha Intake Manifold Upgrade Kit enables your SVHO engine to produce more horsepower by delivering increased air flow and boost pressure (+1lb). Precision tapered billet sleeve directly replaces restrictive mesh element in intake manifold.

rivaracing.com

 

[FSH 210 Sport]

I was talking with my friend earlier today and he pointed out that if you put an opening in the front of the engine compartment you’d also get a lot of noise as well.