15 hp or 20 hp

[Old Salt]

I have a 9.9 nissan on a 14' fiberglass boat I use on local lakes. The 9.9 almost but not quite gets it on plane when I have another person on board so I want to move up. I heard a 15hp is not much more than the 9.9 on power. Should I go to a 20hp or will 15hp make a difference. Don't want to spend more money than I have too.<br /><br />Thanks for any help

 

[OBJ]

Re: 15 hp or 20 hp

A cold snowy good morning old salt.<br /><br />Take a look at the engine set up on the boat. Is the Anti-cavitation plate even with the keel? If it sets below the keel, try raising it up. This will mean rasing the motor on the transom. You can also try different settings with the tilt pin that is located at the bottom of the transom brackets.<br /><br />Sometimes the above helps. Keep us posted.

 

[JB]

Re: 15 hp or 20 hp

Ahoy, Salt.<br /><br />If tweaking your rig doesn't help. . . <br /><br />Most 15s are on the same block as a sister 9.9 and don't offer much more torque. Improvement in hole shot would be minimal.<br /><br />I would look for a larger displacement engine; 18 or 20 IF your boat is rated for it.<br /><br />Good luck.

 

[DJ]

Re: 15 hp or 20 hp

Ditto JB,<br /><br />There is a huge difference between most 15's and 20's or 25's.<br /><br />The 20's and 25's usually have much larger displacements and will "lift" much heavier loads.

 

[rickdb1boat]

Re: 15 hp or 20 hp

Just for comparison, I have a 1967 14' fiberglass Wellcraft(Don't know weight) with a 1989 28 HP Johnson on it and it planes out real quick and runs about 24 MPH. I too think you are underpowered for that boat. I would get a 20 HP at the least for your rig. Put another person or two in it and you will need it!

 

[WillyBWright]

Re: 15 hp or 20 hp

Typically, a 9.9 on a light rowboat might plane you off of you're alone. A 15Hp should, but add another person and it probably won't. To cross the threshold, you need about 20Hp.

 

[cobra 3.0]

Re: 15 hp or 20 hp

Old Salt, what's the boat rated for? I too think the 15 is too little.

 

[bossee]

Re: 15 hp or 20 hp

Hi,<br />You probably need 20 hp to comfortably plane and maintain plane with two normal weight persons onboard. <br />If Your boat is rated for it: <br />For example Honda BF 20 hp (4-stroke) is not so heavy weight (Short shaft: 46 kg/101 lbs, Long shaft: 49 kg/108 lbs).<br /> http://www.honda-marine.com/mod15_20hp.htm <br /><br />But If you prefer 20-25 hp 2-stroke (not so expensive) check out:<br />Mercury 25 Classic (52 kg)<br /> http://www.mercurymarine.com/mercury_25_classic <br />Yamaha 25 hp (48 kg)<br />http://www.yamaha-motor.com/products/subc atspecs.asp?lid=5&lc=otb&cid=20&scid=11&but=42&year=2004&cat=Two+Stroke+Series&scat=Portable<br /><br />If You have the money the Honda BF20 is probably a very good (portable) outboard - low emissions, rather quiet, rather low vibrations and should comfortably get your boat up on plane with two persons.<br /><br />Have You found any 20 hp 2-strokes?<br /><br />15 hp 2-troke will probably be a little to weak for two persons onboard and maintain plane without rather high RPM (higher sound level and higher fuel consumtion also).<br /><br />If You need to take the outboard home often You probably will find a 50 kg outboard to heavy. Then a 15 hp 2-stroke, like Yamaha 15F (36 kg), will perhaps be an alternative.<br /><br />Good luck!

 

[AW]

Re: 15 hp or 20 hp

You can usually get a boat to plane by adjusting (1) load distribution, (2) trim angle, (3) prop pitch, and (4) adding trim tabs.<br /><br />How do you feel about your top end? The price difference between a 15hp and a 20 or 25 hp is usually small, and more hp helps both ends.<br /><br />I have a 13' Whaler with a Johnson 15 that planes well with 4 people totaling over 700lb plus gear. I also have a 14' Grumman aluminum with a Johnson 8 that planes well with 2 adults. Both boats are fairly wide and flat, giving a lot of lift.

 

[Old Salt]

Re: 15 hp or 20 hp

Thanks for all the great replies. I should have mentioned the boat is rated for 40 hp. It looks like I'll get a 20 hp if I can't tweak any more perfomance out my 9.9. There are several 20 hp Mercs listed on iboats so I might try them.<br /><br />old Salt

 

[flydangler]

Re: 15 hp or 20 hp

Don't want to spend more money than I have too.

Before spending the big bucks to upgrade try tweaking your rig as others have suggested, and think about spending the $25 or so a set of stabilizers (like the Doel fins) would set you back. <br /><br />

The 9.9 almost but not quite gets it on plane when I have another person on board

If this is true then tweaking and stabilizers just might do what you want and save you a bundle in the process.

 

[cobra 3.0]

Re: 15 hp or 20 hp

I dunno... a 9.9 on a boat rated for 40? Why not find a good deal on a 40?...or at least a 30. I had a 1988 30 hp Johnson two stroke. I was one great engine...smooth quiet...I could even troll with it.

 

[rickdb1boat]

Re: 15 hp or 20 hp

Agree with cobra! Nothing can substitue for raw HP. Go with the 20 or 30 HP. They are a dime a dozen....

 

[Jdeagro]

Re: 15 hp or 20 hp

Old Salt;<br /><br />I have a 9.9 Nissan on a 10' infaltable with a soft floor. Not known for planing well. It planes fine with two people (I am 240lb)but this is the first boat for which we developed Smart Tabs. It would not plane without the trim tabs.<br /><br />As for the motor, the 9.9 hp has a different cam attachemnt than the 15 hp on the throttle cable. In short it does not allow the carb to open all the way. You can check this by simply removeing the cover and holding the throttle handle open, then moving the linkage on the side of the carb by hand. It will open more.<br /><br />The problem is that the motor does not develop additional HP until your reach the higher RPM's, which will do no good when trying to get on plane. Low end torque is the same! The trim tabs will get the boat on plane easily. Check this site for pricing, or go the WWW.nauticusinc.com for other dealers and retailers. Use ST780-20 for this application.

 

[flydangler]

Re: 15 hp or 20 hp

Old Salt,<br /><br />Looking at Coast Guard standards for hp ratings for your boat to be rated for 40hp it would have to be at least 54" wide and 20" high at the transom, and that would be for remote steering only. Now I'm assuming, seeing as you're using a 9.9hp motor, that you're set up for tiller steering so it looks like about 25hp is really your maximum safe limit. <br /><br />If your transom is only 15" high and/or less than 54" wide the safe limits drop significantly.<br /><br />See http://www.uscgboating.org/regulations/boatbuilder/part1/reg33_183_4a.htm for full info.<br /><br />Good luck, and stay safe!

 

[MarkAB]

Re: 15 hp or 20 hp

I bought a 10ft tri hull bass boat with an 8hp motor. I also almost could get the boat to plane with one adult after adding a hydrolfoil and re propping. I make the wise decision to get a 25 (max hp rating for this boat) and now will never look back. I found that the boat was slightly unstable so I put the 8's hydrofoil on, and now it's a dream. It's also nice to be able to plane at 3/4 throttle.