OVER PROPPED DT 150 ss? HOW BAD FOR MOTOR?

[hankll]

Motor revs are topping at 4600 WOT after trimming up. Motor running good, nice rooster tail but boat bouncing a little so have to trim back down brings revs to 4200. Mechanic says over propped, I agree based on hole shot, long and slow to plane.

Question: On a 19'6 fiberglass Bass boat, 2 people, fully gassed, 36 gal. and fishing gear, is this too hard on motor if I leave it for now, and deal with prop issue later?

Question: On this Suzuki DT150 SS, mechanic says I can bend throttle stop on bottom carb and it'll increase horsepower up to 200 hp and that might give me more power and offset the need for prop change - Is that an ok thing to do?

 

[deejaycee_2000]

Re: OVER PROPPED DT 150 ss? HOW BAD FOR MOTOR?

well, what pitch prop are you running? ..... you should be able to push at least 5500 - 6000 rpm ......

No it is not hard on the motor, and no do not bend the throttle stop, you will fry your motor sooner or later if you do that ......

 

[hankll]

Re: OVER PROPPED DT 150 ss? HOW BAD FOR MOTOR?

Well, I wasn't sure, it seemed to run well, at that 4600 rpm level and I was going 45 or so, plenty fast enough for me. Any faster it'd be time to get a motorcycle helmet.
As far as bending the throttle stop tab, I'm a firm believer that the word "carburetor" is french for "leave the #### alone", So as long as power is good why mess with it. That mechanic I was talking to was a Suzuki dealer mechanic and not the guy I was using for repair issues on my motor. I had been told that the DT175, and DT200 were basically same engine only with different carbs.

 

[hankll]

Re: OVER PROPPED DT 150 ss? HOW BAD FOR MOTOR?

Oh, sorry Deejaycee, I don't know for sure what pitch the prop is. its what came on it, and I assumed it would push my 19'6 boat fine since it was originally on a 17' boat. It's a stainless, but I don't know how to check for what pitch it is.

 

[grid]

Re: OVER PROPPED DT 150 ss? HOW BAD FOR MOTOR?

Nice advice with the throttle tab; he must be related to the dealer in CA who'd guaranteed 10MPH for $100--then re-drilled the speedo pickup hole. There are substantial differences between the 150/175/200, carbs being one, oil pumps to keep up with carb flow, etc. And, if you wanted to achieve that horsepower, add all the different items together and you'd find it was exactly the price increase between models! On your prop, you should see etched on the side of the prop something like 3X14 1/2X19 (or other pitches). Maybe it's a 4-blade, in which case coming back to a 3-blade might be advantageous on your hull. In any event, every inch of pitch equals roughly 100 RPM per blade (and there are other rules of thumb, equally accurate), so going from 19" to 17" would give you another +/- 600RPM with a 3-blade prop. Make sure you get the RPM up into the upper 5000's to prevent excessive side-loading of the pistons.

 

[Captain Paul]

Re: OVER PROPPED DT 150 ss? HOW BAD FOR MOTOR?

I only see about a 400rpm differance moving from my 21" 3 blade to a 19" 3 blade. I think what's important is to have your boat run at max rpms when you are wide open. If you run less pitch, you will see more rpm's, better hole shot, faster plane, all of this with all the gear you carry. You may not even lose that many mph's, since you run 4600 now, and the motor should be running around 5500 I would think. Do you know what max rpm's should be?

 

[hankll]

Re: OVER PROPPED DT 150 ss? HOW BAD FOR MOTOR?

I was told max was 5500-5800 rpms, and my mechanic did mention the piston side torquing could eventually score cyl wall. I'd never heard of that before, but then I'm not experienced at all with 2 cycle and no experience with marine. Issue for me was how severe a problem would it be if I don't attend to it now and deal with it later after my wallet has time to breath before I start extracting more money for the prop issue? AS in will it hold till winter when I won't be using it regularly and I'm dealing with maintenance issues. My usage now is mainly gonna be 2-3 times a month for fishing and I'm not doing tournament fishing by running hard toa spot and running hard to another spot, but mainly 3k revs where I go up on plane but not busting tail getting anywhere.

 

[hankll]

Re: OVER PROPPED DT 150 ss? HOW BAD FOR MOTOR?

oh, BTW, Grid, yea, I was thinking the mechanic might have been shooting me some BS, since my mechanic was in earshot and didn't chime in with an affirmative. I trust him pretty good, and I think he's been pretty good about giving me "good" advice so far.

Prop doesn't seem to have any etch of numbers on its surface in exhaust area of hub or on prop outside itself. maybe in the lower unit end of inside hub part?

Stainless 3 blade is what I have.

 

[yamamarinetech40]

Re: OVER PROPPED DT 150 ss? HOW BAD FOR MOTOR?

This is very simple, everybody is telling you the same thing, you need to get your RPM up at least 600 and really 800 or more....take the prop to a prop shop, spend 35 to 60 bucks and get 2 or 3 inches of pitch out of it...you won't go any faster and your engine will give a sigh of relief....

 

[hankll]

Re: OVER PROPPED DT 150 ss? HOW BAD FOR MOTOR?

THANKS Yam, Didn't realize you could change pitch of same prop. Simple and cheap, good deal, thats why I hang around this forum.

 

[downeaster]

Re: OVER PROPPED DT 150 ss? HOW BAD FOR MOTOR?

You need to drop back about 2 inches of pitch,, and should gain 400 to 500
rpm with each inch of pitch. yamamarinetech40 is exactly right on his
eval.. A drop back of 2 inch would put you about on the money.