Exhaust Relief Port/Holeshot? - long read

[AZ Intimidator]

Having a hole-shot problem. Doesnt seem to happen all the time but the majority of the time for sure. I have a 21ft Gambler boat which is already heavy in the rear with a Merc. 225 EFI on the back of a hydraulic 10" jackplate. Currently running about 3in below pad but I dont generally move the jack plate at all, seems to run best at that setting...water pressure, speed, handling etc....anyways, when I go to get on pad, I tuck the motor completely underneath (trimmed down all the way) and the motor really burys itself in the water and the port in the back right under the cowling is ALWAYS underwater. See pic below...its the center square port. My question is that if this port is underwater does that exhaust relief port possibly build up enough back pressure from being underwater and that it may be holding back the engine from reaching the necessary RPMs to get on plane? I only ask this because everytime my tournament partner walks up on the front of the bow, the front of the boat drops, the RPMs begin to climb, and im up and running. If we both stay in the seats, the boat will just plow around 2800 RPMs. Just curious if a snorkel type device would help or maybe I need the jackplate set higher at takeoff, then drop it to my optimal running point once im up? Ive tried many different props and pitches PVS plugs, no plugs, thru hub exhaust, over the hub exhaust, 3 blade, 4 blade from 24p to 27p and a 25 Tempest Plus fully unplugged seems to run the best. This is frustrating me though and since my boat doesnt have the Trim Tabs that Gambler is now installing on their boats, I need every bit of help I can get. Thoughts?

http://i69.photobucket.com/albums/i54/jgdpd21/Exhaustrelief.jpg?t=1257873427

[shooter1]

I was having a similar problem on a 492 VS with a little motor. I would have to raise the motor up to get up. I eventully had to have a dual PVS holes put in the prop, and then it would unload enought to spin up and get on plane. With the motor that low you will probably have to put some sort on planing aid on it to help. Also make sure that the motor is all set up right. My little 2.4L that I was running, the TPS is very critical as to adjustment. I can't say for sure on the 3.0L motor cause the one that I've got is new to me, but it is just a thought. By the way I'm running a Tempest 25 on my boat. I had the large vents in it and it dogged coming out of the hole, so I took 1 completely out and it comes out great now. Hope this helps.

Shooter1

[dez nuts]

Having a hole-shot problem. Doesnt seem to happen all the time but the majority of the time for sure. I have a 21ft Gambler boat which is already heavy in the rear with a Merc. 225 EFI on the back of a hydraulic 10" jackplate. Currently running about 3in below pad but I dont generally move the jack plate at all, seems to run best at that setting...water pressure, speed, handling etc....anyways, when I go to get on pad, I tuck the motor completely underneath (trimmed down all the way) and the motor really burys itself in the water and the port in the back right under the cowling is ALWAYS underwater. See pic below...its the center square port. My question is that if this port is underwater does that exhaust relief port possibly build up enough back pressure from being underwater and that it may be holding back the engine from reaching the necessary RPMs to get on plane? I only ask this because everytime my tournament partner walks up on the front of the bow, the front of the boat drops, the RPMs begin to climb, and im up and running. If we both stay in the seats, the boat will just plow around 2800 RPMs. Just curious if a snorkel type device would help or maybe I need the jackplate set higher at takeoff, then drop it to my optimal running point once im up? Ive tried many different props and pitches PVS plugs, no plugs, thru hub exhaust, over the hub exhaust, 3 blade, 4 blade from 24p to 27p and a 25 Tempest Plus fully unplugged seems to run the best. This is frustrating me though and since my boat doesnt have the Trim Tabs that Gambler is now installing on their boats, I need every bit of help I can get. Thoughts?

http://i69.photobucket.com/albums/i54/jgdpd21/Exhaustrelief.jpg?t=1257873427Jack your motor up some when you go to take off you sound like you are burying it to deepin the water for the prop to break loose at all try jacking it up 2in or so and also remove the plugs in your tempest completely it will help the prop to ventilate alittle so it will take off also 3in below the pad in way to low to run try jaking the motor up alittle after you get it trimed out and running you should pickup a great deal of speed and the boat should handle better as well. Dave:thumbsup:

[AZ Intimidator]

There currently are no plugs in the Tempest at all. When I bought the plate, I was told that the optimal running setting was determined by slowly jacking the plateup while running and continuing to do so until the water pressure on the gauge starts to drop, and at THAT point, im supposed to stop. Was I misinformed? I know the EFI motor I have is a low pressure, high volume unit and I generally run right around 9 on the water pressure guage. If I start raising the plate, the guage drops which is what I would expect so I figured better safe than sorry. Looks like that might be my problem and I may actually have a couple more inches I can go before it may jeopardize the water pressure intake. I'll try that this weekend and let you guys know. Thanks!

[Charger200]

Yup bring the motor up on the plate to get it to exhale better. Once your upand running take it back down where you like it. Also try starting the engine with a neutral trim or just a lil negative, this might also help.

when i pull skiers or tubers, i have my engine jacked up a ways to let it breathe better then as soons as i know shes on plane i drop it all the way down so that it has lots of bite.

jay

[sschefer]

Raising the jack plate will reverse the effect of tucking the motor all the way under which is your real problem. Set the trim so it is level with the attitude of the boat at rest. This will give you a starting point that you can refine. You're driving the bow down and lifting the stern in essence you're trying to lift the entire boat and wasting a ton of energy.