78 9.9 evine slow @ WOT

Acton

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Jan 15, 2015
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Ive pretty much thrown ridiculous amounts of money at this thing and still can't find a mechanic who will work on it and address the issue that it only gets to 10mph at WOT. It has a 15 hp carb in it.

I know the carbs cam roller is synched properly. It has 93 psi on both cylinders. I don't know what rpms the thing is running at and the last two mechanics I took it too didnt check.

I took it to a backyard mechanic first, then a liscensed mechanic second. They both found a bunch of issues for me to fix, but at the after paying the bill I'm still going 10mph on a barely 12' aluminum v hull when I started with a engine that already worked for $500.

The first mechanic threw on a new head gasket, replaced the water pump and impeller and put on a new power pack since apparently I had starting issues at that time.

After that I replaced the furl pump and threw a new carb kit in myself. I couldnt get the cam roller to line up with the mark on the cam since its a 78 and there's no adjustment screw on the cam. The engine worked but it out at idle at that point and was slow @ WOT but it got the job done at that point last july.

Skip to march and I finally had the money to take it to a real mechanic. Apparently I had issues with my trottle linkage that they replaced parts in, repaired my recoil unit which worked but had parts misding. They cleaned my carb, and checked the lower seal which was leaking but apparently is holding pressure. They also threw a new prop on, replaced the spark plugs and checked the compression as I requested I requested. They synch'd the cam roller properly and readjusted the slow speed idle needle (?) So now it starts on first pull and doesnt have any issues at idle.

I asked the shop owner if there was any way I could test the motor on the boat in the water before I paid the bill because I was concerned about how fast the motor was goinh to move me @ WOT. The shop owner became clearly irritated when I requested this and told me, "That's not how this works."

When I showed up at the shop I actually got to speak to the mechanic who actually worked on it and he told me in detail what was done. I told him I had concerns about the motor running up to speed @ WOT, and he assured me it would be fine since, "The thing was roaring in the barrel."

So I ended up waiting 5 weeks and paying an $800 bill not knowing that there are ways to directly test the rpms on each cylinder with these small outboards. I cant find any other mechanics in my area who will work on a small older outboard like this.

I live in new york in the hudson valley region. Does anyone know any mechanic in the tristate region or even any mechanic up in the cny/wny region who would actually take a look at the rpms and fix the damn issue? Id be willing to travel to western ct, eastern pa, northern nj or anywhere in ny to get this thing running quick a WOT.

Here is proof a 1977 9.9 evinrude can get a boat larger then mine up to 25 mph

https://youtu.be/M_OZ4Qa7H9g

This is my boat. Granted Im a big guy, I weigh 270lbs, but 10mph?!
 

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Vic.S

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fetch


Its difficult to be sure from the picture you posted but your boat appears to be a conventional displacement type of hull , not a planing hull!

The maximum speed of a displacement hull is related to the waterline length Id have estimated it to be about 5 mph .
 

racerone

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Dec 28, 2013
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Run it with a test prop and check the power output of it.----That should have been done long ago !
 

Crosbyman

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and clean up any crud on the bottom of the boat looks terrible.

did it ever run any faster at one time ?
 

Acton

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Jan 15, 2015
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What about using a tiny tach to test rpms on the water under load? Found info on the device here on iboats.
fetch
Its difficult to be sure from the picture you posted but your boat appears to be a conventional displacement type of hull , not a planing hull! The maximum speed of a displacement hull is related to the waterline length Id have estimated it to be about 5 mph .
Does this give a better view? Found a topic on here where the OP had same issue. He was able to do a few things to improve the speed. http://forums.iboats.com/forum/gener...inrude-2-cycle My boat has only ever gotten to 11mph though, much less than the previous OP started at. Disregard the outboard in the picture, its an older picture before I purchased this outboard.
 

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thumbnut

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Sep 29, 2006
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Betcha the motor is fine..like Vic.S said that hull and speed are mutually exclusive. My '76 15hp on a 1232jon does around 16 with my 190pound body. Add 80 pounds and I bet it will be only 10-12mph. That '78 9.9 is the wet leg mid, not the megaphone style exhaust. And that boat is a lot heavier than my 1232. And you are probably sitting in the back, bow high with a dragging stern maybe?

Besides where are you going in a hurry...only get you home sooner..

Many years ago I put my hurricane 10hp on my 18' canoe and the only thing it did was raise the bow higher and higher and push the stern low and lower into the water. At wot the stern was almost below the water level. Your boat is close to a square back canoe.
 
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Dizz

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Jun 12, 2007
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148
I have a 91 Evinrude 15 HP.
On my 15' mini bass boat with woood floors and carpet,seats,cast deck it will do 17mph gps with 2 people over 200 pounds,and gear.
These motors have 2 different pitch props,mine is the low end power prop.
I bought a new 90johnson 15(same motor) and put on a new Smoker Kraft 14' jon boat,it would do 25mph,as it had the hight top end speed prop,that prop would have issius planning my current boat,
Look up the props,get the power prop,can be bought for about $60,not omc but Solas 9.25x11RP.part#2111-093-11
This will fit your motor.
Like others said,your boat does not look like the type of hull that will plain easily,or maybe not at all.
All that $$$ you spent,maybe a newer boat like a 14' semi V ,or jon.
On another note,I tested the compression on my 15HP a while back cold,and it had over 150psi in both cylinders.Although your motor may run smooth,it would not have full power at your readings,IMHO.It may be putting out much less than even 10HP,I may get tarnished here for that opinion.
Good luck.
 
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thumbnut

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Sep 29, 2006
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I'd start with a 4 blade 7 pitch Solas cause they are easy to find and not too pricey. The stern lift with my 4 blade on my 1232 was a lot more than I thought it would be. It just seems like that boat with 360lbs sitting in the back is really rear heavy..motor included that is..
 
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Acton

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So Ive done some research and I DO want to invest in a new USED boat that would fit a few criteria. Something 14' in length with good stability and something wider then what I currently have. This means Ill be turning to Craigslist.

Im not sure how to identify a vhull that's ideal for planning vs a displacement hull such as is the case with my current boat. Before this I thought there where only v-hulls, semi v's and jon boats. I had a jon boat in the past but it was really unstable so I picked up my current boat.

I found this info on displacement hulls online.

"Rowboats like most displacement hulls go best if the waterline shape approximates that of a canoe. If the rowboat has a transom it is elevated to keep it from intersecting waterflow and causing drag. The pinched in stern therefore hasn't enough displacement to support a heavy motor/pilot combo without severely effecting trim.
There's more. Displacement hulls have rockered bottoms. They work great up to the hull's displacement speed. It usually takes very little HP to get there. Going beyond displacement speed can be done but the power required keeps going up geometrically with each additional MPH. And the hull will not plane so the load on the motor never decreases as it would when you go on plane. A displacement hull at speed will try to climb it's bow wave but never pop out on top so the boat remains on the side of a hill of water and works the hell out of themotor to stay there."

So I understand the concept now but I don't know how to identify a vhull thats considered a pkanning hull vs a displacement vhull.

Otherwise Ill be picking up a new prop as suggested above and running seafoam through the outboard.

Whats the most thorough way to decarb with seafoam? Ive heard turning the engine face down and pouring seafoam into the cylinders after removing spark plugs is best. Cylinders need to cover spark plug holes?
 

Dizz

Petty Officer 2nd Class
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Jun 12, 2007
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I saw a page on-line today that said compression on a used 9.9/15 shoud be at least 90psi.
A used motor with 110psi is considered best in class.
They also said electric start will boost that 15psi.
in any case,93 don`t sound that bad.
My 57 model Johnson 3hp twin has 65psi.
Another option is the newer modified flat bottom V hybirds.
I also have a 1236 flat jon.My like new 8HP rude will not plain it off with 2 people&gear.I went to the Solas lower pitch prop,but have not had chance to try it out.
Bottom line,get a boat newer than Noah`s Ark!
Just kidding.
 

Acton

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This boat is being advertised as a 12' duranatic semi v. Pretty wide for a boat its size with high sides. Would this be considered a displacement hull or a vhull?

I know they say if there is little to no dead drop aft the boat will plane well, but I feel like Im missing something. All the boats Im looking at, including mine seem to be pretty flat in the aft/transom section.
 

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Chinewalker

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It's not a V-hull. V-hulls are called V's because of the hull shape at the transom. That boat is more or less flat at the transom. However, I have a Duranatic 12 identical to that one and it flat out flies with a 9.9, well over 20 mph. Lot's of Craigslist ads will say V-hull because the sellers have no clue what makes it a V-hull. They see the pointy end and think V-hull. It's the shape at the transom that matters... Back to the Duranautic. I go about 240 myself and my boat handles me just fine. It's relatively shallow, though, so avoid putting all your weight on on transom cap. I usually run with my gas tank between the front and middle seats to balance things out a bit.
 
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