1991 88 johnson with jet wont plane out

[Eric Lopez]

So my father-in-law just got himself a new boat, its a 16 ft ski barge, with a 1991 v4 88hp johnson with a jet, it wont get on plane. When we first got it we had to replace the water pump (impeller, impeller housing) and do thehead gaskets, dome gaskets and exhaust plate gaskets, it runs better now than when we got it but for some reason it wont get on plane. our tach doesnt work but it sounds like it goes wide open, when u first mash it wide open it has good umpf, it launches good, but it just wont come out of the water, but once the nose of the boat goes up about a foot and a half thats it, the rpms dont go down they still wind out, we've messed with trimm, different depth of the foot in the water, and we just cant figure it out, any help would be appreciated

 

[Eric Lopez]

Re: 1991 88 johnson with jet wont plane out

seriously can anyone give me any ideas to look for? im new to boats

 

[wanty9999]

Re: 1991 88 johnson with jet wont plane out

i am a newbie myself but have you done a compression check? i see you replaced head gaskets etc so you're compression should be in range, but definitely check that out. that boat should haul ***.

also, from this thread: http://forums.iboats.com/johnson-evinrude-outboards/my-boat-wont-plane-out-reach-rpms-467057.html

The propeller rests on a rubber hub that is designed to take the impact of a hit and destroy the lower unit. Take a scribe and mark the prop in relation to the rubber hub inside of the prop if the marks aren't still aligned then you have a spun hub meaning that the hub is turning without the prop. Make sure the gas tank is venting properly, as well as no restrictions in the fuel line. Could also be a Waterlogged hull. If its only getting 2800 rpms that means it is probably not a waterlogged hull though. Even though the carbs were just rebuilt it could also mean a clog in the high speed jet.

99% spun hub though

 

[AlTn]

Re: 1991 88 johnson with jet wont plane out

compression, spark, fuel..right amounts at the right time. Compression test for each cylinder, spark test for each, plug reading for each. Post back the results and you'll get a lot of help. A working tach would help matters.

All I know about jetdrive outboards is the great negative affect any disturbance of the intake water flow has on the power output. I fish with a friend that has a 20 mercury jet and a large leaf or branch can cut the power in half. Try contacting the folks at outboardjets.com for set up and running info.

You could also have water or water soaked flotation between the inner and outer hull causing the boat to be too heavy.

 

[ondarvr]

Re: 1991 88 johnson with jet wont plane out

Post a pic of the setup. I don't know what a "ski barg" is, but pumps don't work well on all hulls.

 

[boobie]

Re: 1991 88 johnson with jet wont plane out

Do a cyl drop test on it and make sure it's running on all 4 cyl's.

 

[MIsteelheader]

Re: 1991 88 johnson with jet wont plane out

Did you check the obvious, anything stuck on the intake grate? It doesn't take much to make a jet start to cavitate, only a single leaf or piece of seaweed. The clearance between the impeller and the liner would be another thing to check.

 

[Eric Lopez]

Re: 1991 88 johnson with jet wont plane out

we are doing a compression check today, ill post the results, as far as stuff being in the jet drive, ive checked, we ripped the whole jet apart so we could replace the impeller for the water pump, and resharpened the impeller prop. the impeller prop has some cavitation burns on it and the bars on foot of the pump are stiff, ive always seen the bars be a little wiggle, would this make a difference? and how would u check to see if the foam inside the boat has soaked up water?

 

[Eric Lopez]

Re: 1991 88 johnson with jet wont plane out

i am a newbie myself but have you done a compression check? i see you replaced head gaskets etc so you're compression should be in range, but definitely check that out. that boat should haul ***.

also, from this thread: http://forums.iboats.com/johnson-evinrude-outboards/my-boat-wont-plane-out-reach-rpms-467057.html

we have a jet on our boat not a prop so we can run the shallows in the river near us

 

[Eric Lopez]

Re: 1991 88 johnson with jet wont plane out




thats the boat, 16ft ski barge with a 88hp v4 johnson with jet not prop

 

[Eric Lopez]

Re: 1991 88 johnson with jet wont plane out

ok so we just did a compression test, readings came out as such. cyl 1;110, 110,110,110, cyl2;105,105,105,105, cyl3; 120,120,120,120 cyl4; 110,110,110,110. we tested each cyclinder 4 times, those were the readings, also regapped the plugs, i dont know how to tell if the flotation between the inner and outer hull would be wet, its been sitting out of water for some time with the plug out on the back, idk like i said im new to boats

 

[ondarvr]

Re: 1991 88 johnson with jet wont plane out

Let's sort of start over. Did he test drive it before he bought it? Did the prior owner say it planed out? Have you talked with the prior owner to discuss this?

The pics are too small and at the wrong angle to see if the pump is at the correct level, need some from behind and at the same level as the bottom of the hull. When you put the pump back together did you adjust the gap between the sleeve and impeller?

 

[Eric Lopez]

Re: 1991 88 johnson with jet wont plane out

the prior owner stop talking to us once we left his place, he was suppose to send us the cover for it and never did. no test drive before buying, but right off the bat when we took it on the water it never did get on plane.

but, good news, today we readjusted the carb, regapped the plugs, adjusted the sleeve and impeller (closed the gap) also honed the impeller and did the compression check, we took it out on the water and we got it to "almost" plane out today, we had to trim it out all the way and then it almost went on plane as long as u left it at full throttle, so tomorrow we are going to raise the whole thing till the foot meets level with the bottom of the boat.

 

[ondarvr]

Re: 1991 88 johnson with jet wont plane out

I have no idea why someone would put a jet pump on that type of hull. Pumps reduce the effective HP by about 30+ %, so you have maybe 60HP, plus they are very sensitive to adjustments.

 

[steelespike]

Re: 1991 88 johnson with jet wont plane out

If the motor is too low it adds drag and may restrict the discharge.

 

[MIsteelheader]

Re: 1991 88 johnson with jet wont plane out

Another thing to check is that the "bucket" or "scoop" is shifting into the proper position when the boat is shifted into forward. I have seen cables stretch or be out of adjustment causing major performance issues. A good indication of this would be if the boat tends to throw a "rooster tail" more than normal.

Steelheader

 

[ondarvr]

Re: 1991 88 johnson with jet wont plane out

Another thing to check is that the "bucket" or "scoop" is shifting into the proper position when the boat is shifted into forward. I have seen cables stretch or be out of adjustment causing major performance issues. A good indication of this would be if the boat tends to throw a "rooster tail" more than normal.

Steelheader

Very good suggestion.

 

[Eric Lopez]

Re: 1991 88 johnson with jet wont plane out

the "bucket" is in the right position, and the cable is stiff, today we raised the motor to the proper height, tomorrow i will post better pics of the posistion its in, and around here u might find one prop on a ski barge out of 50, normally around here on the feather river in northern california if u find a ski barge it normally has a pump so it can run all the shallow water cause of the shallow hub, u can run in as little as 4-6 inchs of water when your up on plane at full speed.

thanks for all the suggestions they helped alot, like i said ill post pics tomorrow and let u know how she does on the water.

thank you

 

[ondarvr]

Re: 1991 88 johnson with jet wont plane out

I live on a river where only jets are used, so I'm very familiar with them, 99.99% are used on aluminum hulls though, fiberglass tends to not get along well with rocks, especially at planing speeds. I wasn't sure if you were using ski barge as a term to describe the type of boat, or as a brand. Frequently there are locations that have very specific boat needs and/or designs, they make sense for that location, but are far less common or useful elsewhere.

 

[Eric Lopez]

Re: 1991 88 johnson with jet wont plane out

ya our river is a wide shallow sandy river, alot of people do run aluminum but the steady deck on the ski barge allows for better movement around the boat, and have a more shallow hull to run over some tricky spots if the river is at the right height, pretty fun