90 HP 4-Stroke

Picture a brand new 2014 Crestliner 1650 Fishhawk. 90 hp fourstroke mercury on the 25″ transom. I found with full gear and me on board (215 pounds) and a 30# dog I trim up still gaining speed (not cavitating prop) but have to pull back on throttle or trim down to keep the motor at its 6000 RPM redline…. (approx. 6300 rpm wide open/trimmed for full speed) When I had others in the boat the RPM stayed in its limits due to weight and could be trimmed out ok. SO- Is a prop supposed to be sized to handle full cargo and a 200+ # passenger and deliver full performance at max rpm or am I over propped? Or am I totally missing the ball on this and please help.

You probably have a 15 degree prop on the boat and need a 17. the 15 get you up faster but loose tool end. my pro v with 90 i ran a 15 most of the time due to heavy loaded boat and a guy or 2. alone it would reach limits.

I don’t know who you are??? 90 4stroke seems to be way too much motor for the 1650. May be I am wrong and assuming that is a 16 ft boat. I run a 75 on a 17 ft. Have no issues with a 17 pitch. 90 on my boat and I wouldn’t think about going over 17-19 pitch. Again I have never had to deal with going too far up on RPMs

Sorry triple A. This message showed as a pm on my phone. So no disrespect asking who you were. Wish you luck with the boat

I’m not sure you have a 25″ transom height. The literature I have only lists a 20″ transom available. Never-the-less it sounds as though you are underpropped. But to be sure, some details need to be verified. First,what source are you using for RPMs? It should be coming from the motor’s computer control through a smart gauge or a digital readout of similar type ie a computer hooked to the engine control or a Lowrance/Humminbird hooked through an NMEA2000 backbone. If it is coming from an analog device such as a dashboard tach is it highly suspect and could be reading hundreds of RPMs high or low.
But your question really is: Which load should be used to determine the correct prop. Your normal load is seldom the full load you described when you got the engine in its proper range without exceeding its rev. limiter. That load should find the wot at 5500-5700 rpms. You and your dog should see the top revs and no more. But you first must verify the rpms on the tach are accurate. Good luck.

17P blackmax prop. 90hp is the current 2014 MAX transom HP and it is a 25″ transom which is “required” with the 90hp per crestliners website. I am positive its 25″ as the motor is extended shaft and I have looked at the same model with 20″ transoms and its clearly visible.

haha no problem bud. any help appreciated.

you want a prop that works when loaded.

Triple-A,
This sounds like a new rig for you, so consider this. A lot of us keep a spare prop on hand, so keep the one you have now for heavier loads, and get one with 2″ more pitch for when you’re by yourself.

HRG

On our old lund with a 2 stroke 90 horse we run 3 or 4 different props depending what we are wanting to do. A 17 works great for us pulling a tube—boy does it not me. A 19 works with a full crew out for a day of pleasure fishing. Come tournament day it is usually A 23 but we have been known to run a 21. Changing a prop is a 5 minute job so why not use the prop that gives you the performance that you want?

There is no “one size fits all” prop. Except, of course, on a new outboard where they have no idea of the use conditions and owner preferences. Then they take a one size fits all guess.

Obviously, you have a lot of motor for the size of your boat. As others have already said, switch out the prop. There are several prop finder apps out there, but you need to know things like total boat weight, top RPM, top speed, etc, so you need to read/study the app and then go out and do some test runs to gather the required info to make them really effective.

Grouse

I am buying a alumacraft 165 competitor sport with a 90 Yamaha. The dealer said I can try their stainless props until I find the right one. On my old boat with a 75 2 stroke I used a 19p aluminum and struggled to get on plane. I switched to a 18p stainless and it jumped on plane, and improved top end by 2-3 mph. This was all when loaded with 3 guys and gear. I would go with a lower prop so you don’t over rev. and can get up with a load.

Nut