Speed with 9.8 Nissan

[Dave11]

I have a 9.8hp Nissan 4 cycle pull start outboard that I currently have on my 1448MT Lowe. I have added front and rear decks as well as a minn kota endura 45 mounted on the bow with group 27 12 v battery and gas in the rear.

The reason I got the 9.8 hp was so I could use it on some of the hp restricted lakes in my area.
With two guys (say 400 lbs) and tackle, what would you expect to get in terms of speed? Lets say during calm conditions and minimal current. I realize it is not going fly, but I just want to get an idea to make sure the motor is working properly.

Thanks for the help in advance.

 

[Whoopbass]

Around 15 mph with the load you described.
If your by yourself you should get about 18 mph.
I have a 15' semi v set up like yours and I could get close to 18 mph with an older Johnson 9.9.
Heck, you might get 20 mph by yourself since you have a newer motor.

It might take some time to plane your boat out when your fishing with your bud.

 

[Dave11]

Around 15 mph with the load you described.
If your by yourself you should get about 18 mph.
I have a 15' semi v set up like yours and I could get close to 18 mph with an older Johnson 9.9.
Heck, you might get 20 mph by yourself since you have a newer motor.

It might take some time to plane your boat out when your fishing with your bud.

You still think I will be able to go that fast with the decks and other accessories? All the other stuff in the boat has got to be equal to another guy. I didn't clock myself last time I was out, but it seemed slower than I was thinking it would be. Seemed like there wasn't
much of a difference between 3/4 throttle and full just louder.

 

[Whoopbass]

My boat has everything yours will have plus I have a heavy 24 volt Minn Kota Maxxum trolling motor that takes two batteries and it did 17 mph with a 9.9 by myself. When I tested my boat I didn't have any tackle or a cooler so that could make a difference. My deck conversion is pretty light. I doubt it adds much more then 30-35 lbs to the total weight of the boat. I used 1/2" plywood and lightweight brackets to support the deck rather then using thick plywood.

As long as your motor can get the boat up on plane and not push a bunch of water you should see these speeds. Adding that second guy might be a problem. I don't think there is a lot of speed difference between 3/4 and wot with any outboard. Seems like they just get louder and suck more gas with only a 2-3 mph gain in speed.

 

[cyberflexx]

I have a Tohatsu 9.8 4stroke 2009 model with elec. start on a 14 foot Alumucraft with aluminum flooring ( already there when I got it) and aluminum decking ( that I installed) a 30lb trolling motor, DC battery and a small tractor crank battery, Bilgepump, 3 gallons of fuel, 4 fishing rods, 2 small tackle bags and about 8lbs more of things like fire extiguisher, tools, odds-n-ends. We clocked this thing on GPS with 2 guys ( one being 280 and the other about 240 ) going 18mph. At one point we had it up to almost 20mph, but that was when I would lean further up front to help plane it out.. I'm guessing avg. speed would be 15mph..* it might go faster now that I lost 40lbs.. heheheh)

I hope this helps.

 

[Dave11]

Thanks for the reply. Now I have some ballpark idea of where I should be.

Last time out I got a phone gps reading of 6 mph( not sure how reliable that is but it felt like we were moving slow) going against the river current after a night of rain. That was with two of us at about 360 lb total. I felt like we were pushing through the water and not riding on top. I didnt have time to take a reading on the down side because a storm rolled in quickly.

Next time out I am going to do some more thorough tests and play with the trim and weight distribution. I would love to get the speeds you guys get. I only weigh about 170lbs, so I was thinking this 9.9 should push me around pretty good.

 

[Outdoorsman]

Wow...I have a 1446 older Monark Mod-V Hull John Boat with a 15 HP. Evinrude...36 lb thrust trollong motor, battery, and full 6 gallon plastic gas tank and I got max. 19.7 on the gps. It was in mildly choppy water conditions and the bow was down on plane....seemed plenty fast enough for me ......I am thinking maybe 21 - 22 on a clam day....oh yea...I weight about 240 lbs....

 

[Dave11]

Alright. So I have had the boat out a couple of more times and I am still thinking something might be wrong. The fastest I have had it was 12 mph and that was with 2 guys weighing 150 lbs. I have not been able to get it over 10 mph with anybody weighing 200 lbs in the boat (I weigh 160 lb) even going with the river current.

I thought maybe it was a weight distribution issue, but even when the passenger moves to the front or back it doesnt really help that much.

I put new spark plugs, new prop hardware (the older thrust holder was all cruded up), new fuel filter, put some seafoam in the gas. The seafoam seemed to help with low idle. Water pump is working fine.

The motor sounds fine, but I just thought I would get a little more out the engine. Maybe it is working fine and I am crazy.

I would really appreciate any suggestions.

 

[nathanielrthomas]

To me that sounds about right. Maybe you could adjust the pins that control the angle of the engine. Those 4strokes just dont have that much torque.

 

[bobberboy]

I think this may be a subject crazymanme2 (reach him here - https://www.tinboats.net/forum/memberlist.php?mode=viewprofile&u=1634) could help you with. He gave me good advice about the position of my motor (height on the transom) and might have some ideas. I had a Nissan 9.8 but no gps so I never knew how fast it went. If you were really fighting the current on the river I could see that you'd get less speed. It seems with a flat bottom that the current would not make as much of a difference as you described.

 

[Dave11]

Do you think it is worth it for me to buy a compression tester and get some readings? My thought was that if something was wrong internally then I wouldnt even be getting what I am getting out of this motor. I don't know if I have the skills to clean a carb, but I might be able to use the spray cleaner. That said, the motor is only a 2007, how bad could it be. The rest of the motor is very clean.

I feel pretty good about the way the motor sits on the boat. The cavitation plate is just under the bottom of the hull maybe and 1" or so. I have been playing around with the angle of the motor, but havent really found one setting working that much better than the others.

I could try to remove the back deck to eliminate some weight, but I don't think the extra say 60 lbs would make that much of a difference speed wise not to mention the conveinence when fishing.

 

[whitedog59]

Raise the motor until the cav plate is 1" above the bottom. The cav plate should not run under water, it should just skim on the surface. Water running over the cav plate imparts a heck of a lot of drag. If your cav plate is 1" below the bottom, I'd wager the water you have a good bit of spray as the water is hitting the motor about 2-3" above the plate.

 

[Dave11]

Raise the motor until the cav plate is 1" above the bottom. The cav plate should not run under water, it should just skim on the surface. Water running over the cav plate imparts a heck of a lot of drag. If your cav plate is 1" below the bottom, I'd wager the water you have a good bit of spray as the water is hitting the motor about 2-3" above the plate.

Actually, the plate does not run under the water because the motor creates a void from the wake. The water skims the bottom of the plate, but I can see the top.

Plus, the manual for the motor states the following:

 

[whitedog59]

Boater,
I'd love to read that comparison.

 

[user 32604]

Put the 15hp carburetor on it

 

[user 32604]

Put the 15hp carburetor on it

 

[airshot]

Put the 15hp carburetor on it

That doesn't work on 4 stroke engines very well, but it does on two strokes !!

 

[user 32604]

Lol the 9.8 Nissan 4 stroke still has a carburetor

 

[user 32604]

That doesn't work on 4 stroke engines very well, but it does on two strokes !!

Or there is a kit where you change the reestrictor plate and the ecm module i think

 

[Lowrider1]

Or there is a kit where you change the reestrictor plate and the ecm module i think

Maybe some exhaust opening too.

Anyone know if NV has 2 stroke restriction?