I own a 2009 Triton 18HP Explorer.  Its 18.6 ft long and has a Merc Optimax 150. Im the third owner of the boat and know both of the previous owners however there is a little discrepancy in some information i have tried to find out. I actually fished out of the boat with both owners at one time or another before i bought it myself. The original owner was able to achieve around 66 mph at WOT but second owner only around 59-60. Second owner put on a jackplate, first guy ran it without. I have only been able to see 60 on gps. I feel strongly that the jackplate isnt set at the correct height which i will look into. However the original owner doesn't remember what pitch prop was on the boat and the second owner immediately swapped the prop that was on it for a tempest 3 blade 23 pitch before he had even taken it to the water. He traded the original prop and can't recall what it was either. Should i consider looking at a 3 blade 24 pitch for increased top speed ?

Lots of variables, the 1st being what rpm's are you turning @WOT?

Does the boat get up on plane with ease fully loaded?

10% speed loss can be attributed to hp loss, increased weight and load distribution with the same boat and motor.  Check to prop shaft height, start at 3 1/2" level with the plane surface, center hull pad.

Tom

56 minutes ago, WRB said:

Lots of variables, the 1st being what rpm's are you turning @WOT?

Does the boat get up on plane with ease fully loaded?

10% speed loss can be attributed to hp loss, increased weight and load distribution with the same boat and motor.  Check to prop shaft height, start at 3 1/2" level with the plane surface, center hull pad.

Tom

Wot rpm is around 5700-5800. Gets on plane very quick. Had it serviced 2 moths ago. All compression was exactly where they said it should be. Heck it only has 132 hours on it. Talked to a guy at triton customer service and he said the 23 was as much prop as he recommended. Said it sounded like the prop shaft height was too low in the water. Told me to it should be around 2 1/2 and 2 3/4 below pad. Should easily push that boat in the 64-66 range with everything set correctly. Now just for some time off to go tinker with it lol!

Check you water intake port height from the prop shaft centerline. If the lowest port is higher then 2 1/2 inches it will suck in air, not good! You need to plug the lowest part hole if you raise the engine higher. What you may need is more bow lift to have less hull water surface drag and this can be done by cupping the prop.

Try a test 23P, 3 blade SST Tempest + prop from the dealer. I realize you have a Tempest, just need to compare them.

Tom

1 hour ago, WRB said:

Check you water intake port height from the prop shaft centerline. If the lowest port is higher then 2 1/2 inches it will suck in air, not good! You need to plug the lowest part hole if you raise the engine higher. What you may need is more bow lift to have less hull water surface drag and this can be done by cupping the prop.

Try a test 23P, 3 blade SST Tempest + prop from the dealer. I realize you have a Tempest, just need to compare them.

Tom

Yeah he said to keep a check on my water pressure. Ideal is around 15 to 18. Any higher then the foot is too low any lower its too high and sucking air. Hopefully after i set it to the right height ill see the gains i should. 

Before you move the engine height measure it 1st so you know exactly what the baseline is. The jack plate set back gives you more bow lift at 3 1/2" then the engine mounted directly onto the transum at 3 1/2", it's all about leverage. What rpm's do you have when you over trim the engine up and a roster tail starts kicking up?

Tom

1 hour ago, WRB said:

Before you move the engine height measure it 1st so you know exactly what the baseline is. The jack plate set back gives you more bow lift at 3 1/2" then the engine mounted directly onto the transum at 3 1/2", it's all about leverage. What rpm's do you have when you over trim the engine up and a roster tail starts kicking up?

Tom

Never paid much attention because once its over trimmed it almost immediately starts wanting to chine walk. Gonna get a baseline measurement then go from there. 

Chine walk at 60 mph? You better check that Jack plate for tightness, sounds like it maybe loose! Hydraulic or manual stirring? Manual stirring the cable could be worn and loose. Chine walk is normally caused by prop torque tipping the hull to one side and bouncing back and forth, to prevent it you turn slightly to one side wetting the hull and back off the speed a tick while trimming back a touch. None of this should be happening under 70 mph.

Tom

15 hours ago, WRB said:

Chine walk at 60 mph? You better check that Jack plate for tightness, sounds like it maybe loose! Hydraulic or manual stirring? Manual stirring the cable could be worn and loose. Chine walk is normally caused by prop torque tipping the hull to one side and bouncing back and forth, to prevent it you turn slightly to one side wetting the hull and back off the speed a tick while trimming back a touch. None of this should be happening under 70 mph.

Tom

Yeah i did forget to mention that the cavitation plate is bent pretty goon on the left side. Runs true dead straight and making right hand turns but at WOT absolutely any movement or even notion that your gonna make a left hand turn and it starts. Which im in the process of having that issue repaired today or tomorrow. 

Hydraulic steering 

15 hours ago, WRB said:

Chine walk at 60 mph?

It's a Triton.  They're notorious for chine walk.