17" VS 19" prop

[trock84]

I have been trolling with a 19" prop on my tyee and I was wondering if changing to a 17" would slow down, Speed up, or have no change to my trolling speed?

[LMITOUT]

It theoretically should slow your boat down. How much it slows down is tough to say for certain.

Depending on the boat's current acceleration/top speed/max RPM's, changing the pitch just for trolling could mess up those other aspects of performance. If you think the boat is running perfect as is, you may end up with a negative result by changing the pitch and won't be happy even if it slows your trolling down a notch or two.

[trock84]

thanks lmitout

I am just going out for a day of trolling. Not much running around. I will pay close attention to the motor when I am running anywhere.

[marine_man]

Do you know where you're running for RPM at WOT?

You can do what you're proposing, but you'll have to watch the tach and keep it under the manufacturer's reccomended upper RPM limit.

marine_man

[trock84]

I believe I am around 5000 rpm with the 19" and I believe the max is 5400 rpm

[marine_man]

What do you have for a motor? Most specs are 5250, 5500 or 6000.

It sounds like a 17 might be in your best interest given your RPM's.. what's your holeshot like?

marine_man

[trock84]

I tried out the 17" on saturday. the 19" would go 2.8 to 3 mph at idle and 41mph at 5000 rpm. The 17" would go 2 to 2.2 at idle and 34 to 35mph at 5000 rpm. The 17 did very well for a long day of trolling. I have a 1990 merc 115 on a tyee 1750. As for the fishing I did very well but very small eyes and sauger.

I did run into a problem though. On my way back to the landing a alarm went off in my boat. My first instinct would have been low oil but I filled it that morning. So I checked it and I did use oil that day. So now I am at a loss. Any Ideas?

[marine_man]

A couple of things - are you sure you were running your motor "full out" - full throttle, trimmed all the way up until you porpise, then trim back until the porposing stops?

It seems very odd to me that you had the exact same RPM's with the 17 vs the 19, yet had slower speed (which is what I would expect with a 17).

I'm thinking your alarms are unrelated. What type of alarm was it? Was it a continous horn, intermitent, etc?

marine_man

[trock84]

the alarm was continous. So I guess I am bringing the boat in to get fixed. No I was not at full RPM. Yes I was trimed up.

[marine_man]

Continuous is no oil or overheat - so either you were out of oil, the float is stuck in the low position, or the engine was running warm. Sounds like you already checked the oil, so that should rule that out. How long has it been since you replaced your water pump?

Also, since you weren't running at full RPM, who knows if the 17 is the right prop overall for your boat. You need to run it full out, as described above, unless you're running over 5250 rpm.

marine_man

[trock84]

I took my boat to a boat mech. He told me to try and change the oil sensor module. I think is what he called it. So that is comming in tomorrow and I will try that but if that doesn't work he said that it is the oil float. But that doesn't make any sence cause I filled up my oil tank then trolled for 8 hours before the alarm went off. So you would think that if the float was stuck it would have went off right away. I am going to try and run both props at top RPM then give a report back.

As for the water pump. The pump is spraying the water out very well. But I have never changed it and I have owned it for 3 years so I guess I will look at that too.