G-3 1756 with a 1999 Mercury 45 jet? Pics added....

[Walkerdogman85]

I am running this motor on third hole down trimmed all the way down. I too out with 2 guys and fishing gear at 22-23 mph down river. My intake is right at the bottom of my boat. Where should it actually be set at? I have read flush with the bottom and bottom of boat with intake fin pins. I was hoping for better MPH. I have checked impeller clearance and wear ring. Also at top and wide open the motor seems to rev up and down not like cavitation but when it runs on the higher end of RPMs it run better and faster but it's just for short periods. I have removed the carbs and soaked them in cleaner. I'm not sure what else to do now? I don't have much spray now. I'll try to post pics tomorrow...

 

[dhoganjr]

On a flat bottom you should get optimum performance with the intake set with front grate pins even with the bottom of the boat. Take a straight edge (ruler, piece of flat or angle aluminum, steel, board, of whatever you have on hand) and hold it to the flat part of the hull between strakes extending out to the shoe. It should hit at the front pin. All hulls will be different, but that is the starting point. Some can run a little higher and some will need to be a bit lower. If there are any dents ahead of the intake that will make a difference too. With it set there you should be able to move the trim out at least one hole, that will help top end and should still get a good hole shot.

From what I have read and heard G3's are a little heavier, but you still should be getting 27 - 30 mph with that setup.

Sounds like there are other issues. Do you have a tachometer to verify what rpms you're running. Have the fuel lines been replaced recently, ethanol breaks them down over time. Are there any air leaks around the primer bulb, tank venting properly. If it has a thermostat check to make sure it is not clogged with debris, with jets they clog up with leaves, wood, sand, mud, etc.

Hopefully this gives you a starting point. Here is a pic of where mine sets fully trimmed down.

 

[Walkerdogman85]

I am having trouble with my photobucket app, but you can check out the pics by clicking on the link in the original post. I put on a new fuel line, new plugs, cleaned carbs... I started with motor even lower and had a lot of spray. I raised it to where it's at now and gained some speed and lost a lot of he spray.

 

[JL8Jeff]

It says your photobucket story is private so nobody can view it. I had to adjust my 60/45 Mercury 4 times to find the best running position. I also needed to add transom wedges to keep it from porpoising but it now rides the way I like it. I've never checked the speed so I can't really compare. But some of the G3 boats are a couple hundred lbs heavier than my Lowe so I would guess they would be a little slower. It sounds like you do have an issue, tough to tell if it's fuel related or spark related. Maybe try running another fuel tank and fuel line to see if that changes anything or possible have someone squeeze the fuel ball when you get that up and down surge to see if that eliminates it.

 

[Walkerdogman85]

I was able to add the pictures to the original post. I also moved the motor up a hole and now its slightly above the bottom of the boat maybe 1/8" to 1/4". I'll try and post a pic of it later. I'm going to try it later today. I have changed fuel filter and fuel line. The tank is a plastic tank i didn't see anything in it as far as dirt.

 

[Walkerdogman85]

I noticed today while operating the boat, my fuel ball wouldn't stay hard. What should I do about that? Having the motor up a hole didn't seem to gain anything by doing it but didn't loose either.

 

[stinkfoot]

I noticed today while operating the boat, my fuel ball wouldn't stay hard. What should I do about that? Having the motor up a hole didn't seem to gain anything by doing it but didn't loose either.

I had the same thing on 20hp Merc that had been rebuilt at a tech college. Problem was the carb gasket was upside down so the vacuum holes on the head that provide fuel pump pressure didn't line up. Flipped it over and now works fine. Could also be a leak in the fuel line. I'd rather have a hose clip I can tighten than those pressed on ones.

 

[dhoganjr]

If that last pic was where it was set at it was too low. 1 hole up should be close. I was thinking true flat bottom, a semi-v needs to be a bit lower than even with the pin due to the v. Before water was going over the lip, you can easily lose 3-4 mph with them that low.

You should notice an improvement when you get your other issue figured out.

 

[Walkerdogman85]

I took boat out today and I did gain some after I trimmed motor up a bit (manual trim). Also I tightened my breather up a bit in my tank and it seemed to help. Im hoping to figure out rpm issue, I'm thinking it's an air leak somewhere? I do now have more spray than before. Mabye in a year or so I can talk wife into buying a bigger motor!!!

 

[JL8Jeff]

If I trim my motor at all, I get more spray.

 

[dhoganjr]

Use your straight edge again after you trim it out to see where it hits. You may need to raise it more.

When you trim it out the foot moves farther away from the hull. When water leaves the hull it starts upward, so the farther out it is trimmed the more splash you will get when it is too low. With manual trim you want it set to get the best performance, kind of a balancing act. All the way down gives better hole shot, but you lose top end and can cause the boat to plow. Trimmed out gives better top end, but can cavitate while trying to get on plane and cause the bow to ride high. Get it between and raise it more, should cut down on the spray. If it cavitates after you raise it, the sweet spot is between holes. With a jet 1/8-1/4 inch will make a big difference.

When you get it set where you want it you can build a splash guard if you can't get the splash cut down. Most hulls built for jets come with them now.

When you decide to upgrade get power trim, it makes a hugh improvement and gives the best of both.

 

[RiverBottomOutdoors]

I'm sure that middle strake isn't helping things.

My G3 1656 w/ 60/40J is rigged out on the heavy side with 24V 80# TM; 3 batteries; 3 bank onboard charger. Me with 2 men I get 22-23 mph on flat water.

 

[Walkerdogman85]

I also have a trolling motor and 2 batteries, I have thought about taking it off and taking one battery out as i primarily catfish and with it being a 40 lb thrust its more or less useless on the river. I have the trim set to where my hole shot is a little slower but my top end is better. I had it trimmed down all the way on the first run and my hole shot was better but like you guys have said set it in the middle. I guess I'm going to have to face the fact that 28-30 MPH down river with no gear is all I can do with out bigger motor. This is my first boat so i guess it could have been worse.. Thanks for all your help. I'm hopefully going to find top end issue and I'll post back what happens.

 

[Walkerdogman85]

Do you think moving my side console to the front and putting it in the middle will help me at all?

 

[Lil' Blue Rude]

Do you think moving my side console to the front and putting it in the middle will help me at all?

No. All that's going to do is make you go slower. Might help spray but will hurt top end way worse.
Make a spray plate like dhoganjr said and you might raise your motor some more. Usually if you not cavitating out of the hole you can raise your motor up more until it does then back it back down a little bit. You might have to slot the bracket to get the perfect height. Won't hurt anything just lets you fine tune it better.

 

[Walkerdogman85]

I'll have to slot motor bracket or drill new holes in transom to go up any higher. I thought about moving console to the front so I could see better at night running the river. I think i'll just leave it alone though.. I hope to paint the boat soon and but some type of roll on rubber for the floor too

 

[Walkerdogman85]

I ran a bottle of seafoam through the tank and went fishing last night, my buddy 285 me 260, 2 18 pound anchors, live well full of bait and cooler full. Along with all our gear and we ran 25 down river. The motor seems to be running a lot better where it's at!! It feels fast at night on the river....