Changing from 150 to 200 hp - prop pitch need changing too?

[hankll]

I'm changing my 87 Suzuki DT 150 SS factory carbs to 200 hp factory carbs - effectively changing my HP up to 200 hp - Presently running 19 pitch on prop, so will I need to consider changing pitch upwards to accommodate higher HP?

 

[Texasmark]

Re: Changing from 150 to 200 hp - prop pitch need changing too?

What are you trying to achieve? Was your 150 underperforming? If it was running at the upper end of the recommended WOT rpm range then it looks like you have 50 more ponies to feed. If it was lugging, then maybe not.

Mark

 

[hankll]

Re: Changing from 150 to 200 hp - prop pitch need changing too?

Running at 5000 rpm's according to my tach, and speedo says 41-43 .... my boat is 19'6" Procraft, so its fairly heavy. the 150 pushes up to plane ok, and it runs ok at WOT, except idling is poor and seems to load up carbs. What I want is the maximum HP that my boat is rated for, and also hoping for a better idle performance although that may be unrealistic with bigger carbs/HP, but hoping to be able to see a better idle.

 

[steelespike]

Re: Changing from 150 to 200 hp - prop pitch need changing too?

I wouldn't make any changes until you have made the up grade and tested.
How reliable is your info on the carb upgrade 50hp seems like asking a lot from a simple carb change.Especially when you are working with 164 cu. in.The 150 and 200 develope their power in the same rpm band.5,000 to 5,600.My guess is you'll be at the top of the range.
Anyone know the 150 to 200 changes?

 

[Silvertip]

Re: Changing from 150 to 200 hp - prop pitch need changing too?

Just to set the record straight, it's not the carbs that are loading up, the carbs are loading up the engine. If 150 carbs load up the motor, 200 HP carbs will likely make it worse. Engines are all about breathing. To get fuel and air into an engine, the exhaust must get out. That typically means there are ignition, port timing, and exhaust tuner changes as well. Again, if you have poor idle quality now, I can't believe adding 200 HP carbs will help that. I'm not familiar with Suzies so that may not be the case but I really feel carbs are not the only change. I can assure you however, the engine will be as thirsty as the 200. If the gearset in the lower unit is the same on the two engines you might be able to twist a prop with slightly more pitch but run what you have and see what happens.

 

[hankll]

Re: Changing from 150 to 200 hp - prop pitch need changing too?

From what I was told by mechanic that worked on my motor last spring, no oil pump mods are needed and carbs bolt on. The Suzuki block is same for 150, 175, 200 and just carbs are different. Bigger jets, throat are difference in them. The block has full opened reed sets starting at 150 HP - So working from that is why I'm changing - however issue of exhaust breathing capability for bigger HP should be helped since I already have dual spark plugs on this engine. But good idea to see what happens with prop issue before changing to higher pitch. The SS prop that came on it was 24 and motor was originally on a 17' and had to change to lower pitch when it spun the hub while coming up on plane, marina where I was at and only had the 19 pitch aluminum in stock, so that worked ok, but had intended to put a 21.

 

[Frank Acampora]

Re: Changing from 150 to 200 hp - prop pitch need changing too?

Just my humble opinion Hank, but I think you are wasting your money: outboards are not like old autos where bolting a 4 barrel in place of a 2 gave major horsepower gains. I think you will be unpleasantly surprised at the performance with the 200 carbs. They will probably give you little to no performance gain. If you can get them for free or dirt cheap--then--what the hell--give 'em a try.

Now, I'm no Suzuki guru, but they probably follow typical engine design practice. Typically, on an outboard, while the block is the same for a series of engines, the port timing is usually different, the prop is different, the lower unit may have different gear ratios, and compression ratio may also be different. Without the other modifications, carbs alone make a minor difference. It seems to be a pretty common misconception with outboards that changing carbs will magically increase horsepower. Nothing in life is ever as simple as it seems.

But, Hey! I could be wrong. Go over to the Suzy forum and see what they have to say.