handyandy
Well-known member
So recently I finally got around to putting the jet pump on my 1993 60hp mariner that I've had on my boat. So here is a description of the set up 1554 excel boat it has a mod v front that goes to a smooth flat bottom center keel ends about 2ft or so before the back, it is 15ft long 54in bottom width. Gas tank is up front boat sits almost completely level without me in the back. I have atlas micro jacker jack plate only 4" set. The boat is heavy for it's size it's a 1/8"/.125" thick hull, Longitudinal stringers, welded in floor, with boxes going up each side. Great hull extremely tough, but heavy for it's size. It has some dings on the bottom but nothing bad. I previously had a 40hp nissan/tohatsu carbed prop outboard on it. Ran pretty well with it, low 30's with just me upper 20's with duck hunting load (2-3 guys, guns, decoys, and gear so decent load). I figured the hull could work pretty well with a jet being it sits nice and level, it's tough, planes easily, smooth flat bottom, slight mod v front to help disperse air/bubbles, jack plate doesn't set the motor to far back but would allow me to go between prop and jet. Reason I wanted a jet lot of my fishing is done in shallow, snag ridden, sandy/gravel bottom river with some shallow riffles that I can't quiet get through all the time with the prop. But sometimes prop is better for marshy areas I go to hunting where weeds I imagine would cause more headaches with the jet, so that's why I want to be able to switch. I know most don't suggest it you need to pick on or the other.
So I knew the 40 was just enough with a prop so putting a jet on it was out as I figured the power loss would just be too much and would perform poorly. So I figured a 60-70hp engine with a jet would be adequate as they should be around 40hp at the pump. So I hunted around and got a ok deal on a older 1993 60hp tiller steer mariner that runs pretty darn good that had a prop lower on it with a quicksilver stainless prop. So I mounted that on the boat with the prop, and dang the boat scoots with it. Then hunted down a outboard jet for it took a while, but got a deal on used one that was in almost new condition. Clearance between the impeller and liner is nice and tight, very few scratches in the liner, the impeller is in great shape all the shims are on the bottom, bearings are in great shape, only thing I did was change the drive shaft from a long one to a short one.
This past weekend I finally got around to putting the jet on it on the engine. Raised the jack plate up all the way and even set the motor on the highest bolt holes to give me the most room for adjust down or up finitely with the jack plate. Well I got it on got the shift cable and shifter dialed in. Made up a different transom saver for the jet foot. Stick it in the water and man was it disappointing. I knew the jet would be weaker than the prop, but crap I figured a sixty would have the balls to at least plane the boat out. I had a little load in it but not a lot. Just me and duck/goose decoys in the boat probably about equivalent of another guy in the boat. I'm small only weigh 150, decoys maybe another 150, 6-8 gals of gas up front, battery in back, trolling motor up front, so not really a ton of stuff. I know jets are sensitive to their set up, but I tried different trim levels, all the way down up a little. I tried the motor raised up all the way which made it cavitate some, down to much to where it was spraying, where it seemed the best not cavitating not spraying a lot. But I just couldn't get it to plane out. Just didn't seem to have the power which I figured it should have had enough to at least plane out and get into the mid 20's.
The things I really wonder is one my AG outboard jet currently has the 6 5/8" impellar and liner if I'm measuring it correctly which was meant for 50hp varieties of my engine 60hp was suppose to have 6 7/8" impeller and liner. How are you suppose to mesure the impeller and liner want to make sure I'm doing it right? If this is the case and I have a slightly undersized impellar would that slight 1/4" jump in impeller size make that big a difference? The other thing I wonder is I wasn't running any kind of spray/water tab on the bottom of the transom do they usually help that much? I think a tab could make some difference, but I have hard time believing it would be a big enough difference to get the gains I need. The engine certainly didn't struggle at all with the jet open it WOT it revved right up to whatever rpm it was running sounded higher than it ever did with a prop. Can't say as to the exact rpm though no tac gonna order one.
Sorry for the long post just tried to make it detailed and give necessary info. I have read a lot on here and elsewhere on the set up of jets, but I'm still all ears as many of you have much more experience than me. I'm hoping the larger impeller might do it. If so is worth spending the extra on a stainless one or just get aluminum to try it out.
So I knew the 40 was just enough with a prop so putting a jet on it was out as I figured the power loss would just be too much and would perform poorly. So I figured a 60-70hp engine with a jet would be adequate as they should be around 40hp at the pump. So I hunted around and got a ok deal on a older 1993 60hp tiller steer mariner that runs pretty darn good that had a prop lower on it with a quicksilver stainless prop. So I mounted that on the boat with the prop, and dang the boat scoots with it. Then hunted down a outboard jet for it took a while, but got a deal on used one that was in almost new condition. Clearance between the impeller and liner is nice and tight, very few scratches in the liner, the impeller is in great shape all the shims are on the bottom, bearings are in great shape, only thing I did was change the drive shaft from a long one to a short one.
This past weekend I finally got around to putting the jet on it on the engine. Raised the jack plate up all the way and even set the motor on the highest bolt holes to give me the most room for adjust down or up finitely with the jack plate. Well I got it on got the shift cable and shifter dialed in. Made up a different transom saver for the jet foot. Stick it in the water and man was it disappointing. I knew the jet would be weaker than the prop, but crap I figured a sixty would have the balls to at least plane the boat out. I had a little load in it but not a lot. Just me and duck/goose decoys in the boat probably about equivalent of another guy in the boat. I'm small only weigh 150, decoys maybe another 150, 6-8 gals of gas up front, battery in back, trolling motor up front, so not really a ton of stuff. I know jets are sensitive to their set up, but I tried different trim levels, all the way down up a little. I tried the motor raised up all the way which made it cavitate some, down to much to where it was spraying, where it seemed the best not cavitating not spraying a lot. But I just couldn't get it to plane out. Just didn't seem to have the power which I figured it should have had enough to at least plane out and get into the mid 20's.
The things I really wonder is one my AG outboard jet currently has the 6 5/8" impellar and liner if I'm measuring it correctly which was meant for 50hp varieties of my engine 60hp was suppose to have 6 7/8" impeller and liner. How are you suppose to mesure the impeller and liner want to make sure I'm doing it right? If this is the case and I have a slightly undersized impellar would that slight 1/4" jump in impeller size make that big a difference? The other thing I wonder is I wasn't running any kind of spray/water tab on the bottom of the transom do they usually help that much? I think a tab could make some difference, but I have hard time believing it would be a big enough difference to get the gains I need. The engine certainly didn't struggle at all with the jet open it WOT it revved right up to whatever rpm it was running sounded higher than it ever did with a prop. Can't say as to the exact rpm though no tac gonna order one.
Sorry for the long post just tried to make it detailed and give necessary info. I have read a lot on here and elsewhere on the set up of jets, but I'm still all ears as many of you have much more experience than me. I'm hoping the larger impeller might do it. If so is worth spending the extra on a stainless one or just get aluminum to try it out.