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Author Topic:   Prop and rpm
Popeye posted 11-11-2002 01:21 PM ET (US)   Profile for Popeye   Send Email to Popeye  
Hi,
I just repowered my 78 Montauk with a 97 Yamaha 90 hp. I did not get a owners manual and the sealok manual I purchased does not list the rpm for this motor. Anyhow Im quessing it should be at least 5500. The prop on it is a stock 13.25 x 17. My rpm is about 4900 and speed is 37 mph with gps. I run the boat very heavy.
40 gal fuel
15 hp Johnson 2s kicker
400 lbs fisherpeople
150 qt cooler w/ice
32 gal bait tank
200 lbs misc.
Im thinking maybe a 13.25x15 my be the hot setup. What do you think? Also would someone know the gear ratio for the lower end, then I could use the prop calc. in the ref. section. I have the owners manual on order. Thanks in advance.
Mark

Run down hill going home

Bigshot posted 11-11-2002 01:59 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
No need for prop calc. My 89 Montauk with 2 people spinning a 13x17 SS prop ran 5400. Redline is 5-5500. Being you are heavy is why the lower rpm's. If you always run this try a 15 but you may need a 15 SS prop to make it kind of a 16". I think gear ratio is either a 2:1 or a 1.83:1.
Popeye posted 11-11-2002 04:34 PM ET (US)     Profile for Popeye  Send Email to Popeye     

Thanks Bigshot,
I think I will give the 15 inch pitch a try. The boat is just for fishing, do not care about the top end, just dont want to strain motor.
Thanks again,Mark
TightPenny posted 11-21-2002 09:03 AM ET (US)     Profile for TightPenny  Send Email to TightPenny     
Just out of curiosity, where do you put 40 gallons of gasoline on a montauk, and still fish what would appear to be a skinny crew of two.
Popeye posted 11-21-2002 10:26 AM ET (US)     Profile for Popeye  Send Email to Popeye     

Hi Tightpenny,
I hve 28 gals. under the rps and carry 12 gals. on the deck in cans. Before the repower with the Yamaha 90, I had a 1978 85 hp johnson that was pretty thirsty, carried as much as 35 gals on the deck. No need to comment on the dangers of it, been doing it for 22 years.
I fish the boat from San Diego to Morro Bay, and all of the local banks for Yellowfin Tuna, Albacore and Dorado. This was not a good year for me as the fish were outside of my range, about 40 miles, younger and dumber been out 68 miles. The boat has never done anything except take me out, beat me up, and take me home. Switching to Halibut now. Three people, no gas cans, lazy drifts in the Santa Monica Bay, Dreaming of that 22 foot low profile that I always wanted.
Run downhill going home.
Mark.

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