Prop question,90hp yamaha trla 2002

[Libertyisland]

I have a 17' Blue fin aluminum open bow and we just purchased a 2002 yamaha 90hp trla engine (no prop) engine rpm on this site 4500-5500. I found a prop, factory Yam ss 13.75x18 4 blade for around $100.will this be proper?(no pun intended) Thanks

 

[mpsyamaha]

Re: Prop question,90hp yamaha trla 2002

what motor and prop did you have on the boat previously?

 

[Libertyisland]

Re: Prop question,90hp yamaha trla 2002

50hp Force was on it, not sure of the prop size. motor didn't last long enough to test anything.

 

[steelespike]

Re: Prop question,90hp yamaha trla 2002

Looking around I think the 18 is too much prop. I think a 15 would be closer to what you need especially if your putting the family in the boat and doing any water sports.What does the boat alone weigh dry?

 

[Libertyisland]

Re: Prop question,90hp yamaha trla 2002

iboats spec page says 850lbs dry. max cap weight is around 1500lbs and I believe 6 passengers. Not a whole lot of watersports,tow a tube or ski maybe 3 or 4 times a year. it's mostly a transportation boat from the marina to our cottage(about 15 minutes) and out to the garbage dump. We load it up[ pretty good with supplies and the water gets rough sometimes. it is used in the Georgian bay,Canada. The 50 hp Force was useless(for as long as it lasted) Thanks for any info.

 

[steelespike]

Re: Prop question,90hp yamaha trla 2002

I was figuring the boat for about 1,000lbs but if you are hauling supplies and stuff I would still stick with a 15.It may wind up a little tight empty but you can control that and you'll still have some push for a load.

 

[Libertyisland]

Re: Prop question,90hp yamaha trla 2002

Thanks, so a 15 pitch will let the engine spool up to a higher rpm and the 18pitch will make it spin at a lower rpm and lug the engine? I was looking for good hole shot and fuel economy,top speed is not that big of a deal to us. now 3 0r 4 blade ? I will go for ss. Thanks.

 

[mpsyamaha]

Re: Prop question,90hp yamaha trla 2002

i would say a 15p 3 blade prop should be great for your situation. I would think your hole shot and load carrying would be great. Just keep an eye on your wot rpms if you have a light load.

i have a somewhat similar boat.... 16ft fiberglass semi-v that weighs about 750lbs with a 06 yamaha 70hp. It turns a 17p 3 blade, but im about to switch to a 15p because i can get a little more rpms out of it and increase the hole shot. Even now with the 17p on the 70 it planes off quickly.

 

[Libertyisland]

Re: Prop question,90hp yamaha trla 2002

Thanks for the info, I will look for a 15p. But I may still buy the 18p for a back up prop (emergency) I figure 100 bucks for a ss spare will be ok, and it will get me back to the marina if I spin a hub or worse... Thanks for the info to a newbie..

 

[steelespike]

Re: Prop question,90hp yamaha trla 2002

If you want to refine your setup for best performance/ecomomy.the verticle height of the motor is critical.Start with the antivent plate(just above the prop)even with the bottom of the boat.THen raise the motor a hole at a time until just before ventilation becomes a problem.Just be sure it continues to pump water.A good stainless prop will help to fine tune this setup.
The idea is to have the least amount of motor in the water without venting problems.With some luck you could realize around 6 mpg.at cruising speed with a light load.