Can I get more HP out of my Johnson 90?

A couple years ago I bought a 19' 1995 cc fiberglass Hydraskiff with a v4 90 hp Johnson. I think the motor is undersized for the boat. In calm water and adjusting the trim I can get up on plane and do around 25mph. If the water is rough or if I have more that 3 big people on the boat, can't get up on plane and I just plow through the water. I have switched props and had motor checked, it runs good. Is there any way to develope more horsepower from this motor?.

Re: Can I get more HP out of my Johnson 90?

short answer...no...long answer yes.... but the yes isnt worth it.... you sell the 90 and buy a 115 or 150. You probably wont have to throw that much more money at the larger motor from what you get for the 90!! might even put cash in your pocket depending on how luclky your timing is.

I turned a 90 hp ocean pro into a 115 hp...but it was carbs, and heads and Reporting of the cylinder sleeves.... and that involves a complete motor tear down...hardly a walk in the park.

I did it because one piston was slapping its skirt and the motor had to be torn down anyway.

but i am really thinking if you boat is that much of a dog with a 90... and everything truely is running well...then you will need a 150-175 hp . can we assume the 90 is also a mid 90's motor? what model # is it?

when you say you had the motor checked...that is relative to us...by whom? and and how? what was checked?

what is the rpms your motor will max out at?????

do you have a picture of the back of your boat??


bob

Re: Can I get more HP out of my Johnson 90?

Like bob said, rpms at wot are key to know if your engine is set up properly.

Re: Can I get more HP out of my Johnson 90?

What's the boats maximum horse power rating ??

Re: Can I get more HP out of my Johnson 90?

First question is: What is the boat rated for?

Most 19' are rated for 150hp or more. The 70% rule of thumb calls for 70% or more of the rating. If your boat is rated for only 150HP the minimum HP for satisfactory performance is 105HP. It is even worse if you are rated for 175 or 200HP

You are underpowered enough to explain the lousy performance. No amount of fiddling would overcome that.

Re: Can I get more HP out of my Johnson 90?

OMC made two types of 90 engines in 1995. The old crossflow type and their new looper type. Which one do you have? Would be helpful to know the model number. Agree, helpful to know your WOT rpm's.

Re: Can I get more HP out of my Johnson 90?

I have an '85 V90 on a 21'CC Tinny. It pushes me up to 40mph.

Sounds like the motor has an issue, maybe one cylinder not running or the boat is really really heavy. Any chance you're water logged?

Re: Can I get more HP out of my Johnson 90?

64osby said:

I have an '85 V90 on a 21'CC Tinny. It pushes me up to 40mph.

Sounds like the motor has an issue, maybe one cylinder not running or the boat is really really heavy. Any chance you're water logged?

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Agree. Something's up with that motor or your boat is waterlogged.

Re: Can I get more HP out of my Johnson 90?

if i were you, id trailer the boat to the scrap yard and pull it up onto their scales. and dissconnect the truck...see what your trailer-boat-motor combo weighs

for rough reference you can figure what the motor, and trailer weigh and have a good idea what the boats portion is

I have done it a few times... and they didnt charge me at all.... takes 5 minutes tops

if the number are really really high...you can just drive away fast and leave the boat!!!!


ha ha..I make joke!


bob

Re: Can I get more HP out of my Johnson 90?

^^^:laugh::laugh: Good one Bob.

My local gravel pit also weighs for free.

Re: Can I get more HP out of my Johnson 90?

that boat is about 30 hp under min 70percent rating.boat should weight approx 1645 and is rated for 150 hp.start looking for a 120 plus motor ,you will never be happy with the 90 no matter what you do.

Re: Can I get more HP out of my Johnson 90?

Thank you all for your help. I have had the motor checked for compression and mechanic told me it was fine. I can get it up to around 5500 rpm when it gets up on plane. When I first push the throttle all the way up, it goes to 3500 rpm then when will slowly climb to max as long as water is smooth then goes around 26 mph. I did have the hull checked to see if it was water logged and it was OK. Max rating is 150 hp. I think I'm just underpowered. Went to the big Balto Boat Show last weekend and talked around and have some guys looking for a bigger used outboard for me. I guess this is what happens when you don't know enough about something and buy used. Seems pretty clear that the guy I bought it from knew about the problem. When I test rode it with him, we stayed on smooth water in a creek. I had my wife and kids on the boat and he did not go out into the rougher water in the bay saying he did not want anybody to get wet. Very considerate of him, eh?

So I had 1 boat dealer offer me $800 for my current moor toward a trade in. Any Idea what it's worth? Had another mechanic tell me a newer 4 stroke 90HP would make a big power difference because they put more power at the prop than an old 2 stroke.

Re: Can I get more HP out of my Johnson 90?

george1857 said:

Thank you all for your help. I have had the motor checked for compression and mechanic told me it was fine. I can get it up to around 5500 rpm when it gets up on plane. When I first push the throttle all the way up, it goes to 3500 rpm then when will slowly climb to max as long as water is smooth then goes around 26 mph. I did have the hull checked to see if it was water logged and it was OK. Max rating is 150 hp. I think I'm just underpowered. Went to the big Balto Boat Show last weekend and talked around and have some guys looking for a bigger used outboard for me. I guess this is what happens when you don't know enough about something and buy used. Seems pretty clear that the guy I bought it from knew about the problem. When I test rode it with him, we stayed on smooth water in a creek. I had my wife and kids on the boat and he did not go out into the rougher water in the bay saying he did not want anybody to get wet. Very considerate of him, eh?

So I had 1 boat dealer offer me $800 for my current moor toward a trade in. Any Idea what it's worth? Had another mechanic tell me a newer 4 stroke 90HP would make a big power difference because they put more power at the prop than an old 2 stroke.

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do not believe that last statement....he sound slike the brother of the guy who sold you the boat in the first place!!

youd be going BACKWARDS a HUGE step going to a 4 stroke 90 hp!!!! in terms of your issues now.

an e-tec 150 hp would be way better....and something id recomend.... the yamahas and suzukis , i have GREAT things about...but they are MUCH heavier..

you never said what your motor model # is.

your motor might be worth $2500!!!!!!! maybe more depending on condition

the model # will help.

the four strokes are reliable, easy maintence, clean running motors, but they are not more powerful than the 2 strokes and they are a lot heavier

bob

Re: Can I get more HP out of my Johnson 90?

that new mercury 150 four stroke looks really nice... 183 cubic inches!!!! only 455 lbs...if you were considering a four stroke...

BUT personally, not knowing your budget, you have already consigned yourself to a mid 90s motor when you bought this rig....so if you ended up with a mid 90's 150 hp.... you wouldnt be far from where you started.. I think it would be easy for you to buy a rebuilt , warrantied 150 hp ocean runner or ocean pro or even Intruder for about $4K . it will weigh about 100 lbs less that a four stroke, and be way more powerful. and LOT cheaper. and if you sold your motor on your own, you might be out maybe $2000 or so..maybe a little more with rigging....but if you have the money.....brandy new is always fun!

good luck

bob

Re: Can I get more HP out of my Johnson 90?

I may have missed it, but what is the max hp rating on the boat ??

Re: Can I get more HP out of my Johnson 90?

boobie said:

I may have missed it, but what is the max hp rating on the boat ??

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Think somebody said 150? Ya so 90's a lil low ...

Re: Can I get more HP out of my Johnson 90?

george1857 said:

I did have the hull checked to see if it was water logged and it was OK.

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So how did they check this for you?

Did you weigh the boat?

Have you checked if your prop is spun?