what prop size should i use

tdoucette · Jul 12, 2012

i have a 1972 srv 200 with a inline 6 165 hp some one changed the out drive to a 888 and kept the prop that came with the unit i am wondering what prop i should use with this motor and boat combo right now it is a 19 pitch and wont get out of its own way i have rebuilt the carb and took the screen off the end of the pick up yube it runs great now other than the slow get up and go had four people on board when i took it out it did nothing but stand strait up let 2 people get out and it barley planed off and it hit 23 mph rpms about 3200 what should i do

steelespike · Jul 12, 2012

Re: what prop size should i use

I think the 888 had a 1.5 gear ratio.
It would be good to see light load wot run, remind us of the prop size and tell us the rpm and gps speed.
It will help us tell if a prop change will help you out.

tdoucette · Jul 12, 2012

Re: what prop size should i use

steelespike said:
I think the 888 had a 1.5 gear ratio.
It would be good to see light load wot run, remind us of the prop size and tell us the rpm and gps speed.
It will help us tell if a prop change will help you out.

ihave done with alight load 1 man and small kid and it was 19 pitch 3200
rpm and 24 mph trimmed out to the max on gps rpm maybe off a little relying onboard tach

steelespike · Jul 13, 2012

Re: what prop size should i use

Lets assume the specs are accurate ,within reason and your 37% slip is due to the low rpm.
It appears you need to make up about 1000 rpm and you could do that with a 14" prop.
At 4200 a 14" prop could make about 33 mph.guessing 10% slip.
A 1.65 ratio if you could make 4200 rpm with the 19" guessing 10% slip you could make about 41.
I have a feeling it would struggle to do so.

90stingray · Jul 13, 2012

Re: what prop size should i use

What steelespike is saying is that your gear ratio is off... and a prop change is not going to make it right. I assume this boat is new to you? Some people dont know there are different ratios for different engines. So they slap a usable leg on thinking it will work... and when it doesn't ... well it gets sold. I think something from a v6 or even a 4 cylinder would do better for you. Tough spot...

tdoucette · Jul 13, 2012

Re: what prop size should i use

i went on the mercruser site they said that 888 is ok for that motor and i have got a used 14x17 stainless prop. In the sea ray prop selector it said 17c pitch just found it on the web it list all the out drives and motors for that year and model do you think this prop would do it i hope

Maclin · Jul 13, 2012

Re: what prop size should i use

Just going by the numbers you are getting a 2 inch drop in pitch will help a little, but still not get you to top RPM's of ~4100 for that engine.

What were the top rpm's and speed before this change? Did it take off ok before this?

tdoucette · Jul 13, 2012

Re: what prop size should i use

on my other post i made a mistake the prop pitch was a 14x21 not a 14x19 at light load 3200 rpm and 24 mph with a light load sorry about that now i got a 14x17 stainless couldnt beat the price brand new in a box one problem it hits my zinc the man told me to use a flat zinc does that sound right and will that help my problem

jimmbo · Jul 13, 2012

Re: what prop size should i use

First I would make sure it is firing on all six cylinders, that it's compession is good, and that the timing is set correctly and the advance weights are free and working. Then I would verify what the gear ratio is. An 888 probably has a taller ratio(lower numericly) than a 165, and probably not by very much, so the variance should be correctible with a different prop.

90stingray · Jul 13, 2012

Re: what prop size should i use

tdoucette said:
the man told me to use a flat zinc does that sound right and will that help my problem

Do you have power steering? If so, get a flat one. If no ps, get the offset tab. But if you have a 17 ss... give her a shot. Even for a quick check... you could cut off that tab to clear the prop. I have done that while waiting for parts to show up. Hope the 17 does the trick for you (Fingers crossed)

tdoucette · Jul 13, 2012

Re: what prop size should i use

ok cut off the zinc put on th ss 14x17 went out and wala it is going with 5 grown men on board 3900 rpm without trim and ill go about 31.6 mph when i go to trim it porpususes looks like i am on the right track should i put som dolphins on it to stop porpusing thank guys for all your help it is greatly appreciated you are very khowledgeable again i cant thank you enough do they make a zinc offset that is to clear the prop or should i leave it cut

what prop size should i use

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