Wrong Gear Ratio

Hello:

I have a 1981 Glastron SSV 194 w/ a 228hp, 305 V-8.

The guy I bought it from replaced the upper drive unit with one from a 165hp inline 6. The inline 6 gear ratio is 1.62 and the V-8 ratio is 1.47. I asked and he said he didn't change the gears, so I'm assuming that I am running 1.62 gears in the boat. As it sits, there isn't a "Flat" spot on the throttle where you give it a little throttle and all it does is make a little mor noise (Like going from plowing to planing) It came with a 19 pitch Vengance (I think) prop. I have not yet run it at WOT. I have had it to 4k RPM, buit don't really like to push it that hard. It cruises great at 3k RPM at 31 MPH. Both on plane picturesw are at cruising speed.

The question I have is, how much change is there in the speed / RPM from the gears I have and the gears I should have? The hole shot is very impressive for a 19'er.

Thanks for your imput and advice.

Craig

Re: Wrong Gear Ratio

Anyone??

Re: Wrong Gear Ratio

Some of the later model 200/5.0L came OEM with a 1.65

Re: Wrong Gear Ratio

Ok. Would I gain or loose anything by changing it? I never did really open it up to see what WOT was. What is the WOT range??

Re: Wrong Gear Ratio

4200 to 4600 is the WOT rpm for the 228. As long as you are getting the proper WOT rpm and not lugging the engine, and you are happy with the way it runs. Why worry?
If you are low in WOT rpm, then you really don't want the 1.47 ratio, and you should be. WOT is how you check if you have the correct prop or not. Prop forum is where you need to go for different props if needed.

Re: Wrong Gear Ratio

Thanks Don. Just out of curiosity, how much would the 1.47 lower the WOT?

Re: Wrong Gear Ratio

Have no clue how much, you would just have to change props to get the rpm back up where it's supposed to be.

Re: Wrong Gear Ratio

Hey 79Merc, do a search on the web for Prop Calculators, they can give you a cloe enough estimate on what changes do what.

Re: Wrong Gear Ratio

I did that and some of them said it was a 1.47 and others said 1.62. I used the cruising perameters I know since I have never had it at WOT.

I guess I'll have to count the teeth in the spring.

Thanks for your assisitance.

Craig

Re: Wrong Gear Ratio

Without accurate prop slip % you will not be able to determine the drive ratio. But, you can use the calc-er to see the differences between two ratios, or other changes.

Put in the parameters (pitch,ratio,slip, MPH or RPM) as if it is a 1.6 ratio, and let it calc MPH or RPM by leaving one of those blank. Then with all those parameters the same put the different ratio in, leave MPH blank and see the difference. Then leave all the parameters the same but leave the RPM blank and see the difference there at the same MPH. After a few tries you will be able to see the relationship between the ratio and pitch and RPM and MPH, and the relative results when pitch or ratio is changed.

Re: Wrong Gear Ratio

Oops,

meant to oput this link in that last post....:

http://www.marksmarineinc.com/prop_calc.aspx


Calculators like this can show relative changes, they are only as accurate as the info given of course, but using a normal prop slip constant of 12-15%, even if it is not the "real" number from your boat in operation, will produce numbers that show the relative differences between two calcs.

Re: Wrong Gear Ratio

My 19ft bowrider came with the 305 and 162 ratio. Works perfect, turns a 21p prop to 4700 rpm