VIP 21' Center Console with 115HP Mercury Tower Of Power Inline 6 - Max Speed?

[frankrizzo]

I can only seem to get my boat up to 17mph. I need to know what could help assist in getting a higher top speed. I cleaned my carbs and adjusted the screws to 1 and 3/4 turns out. I replaced all fuel lines and filters. I put in a new stator and changed a bad switch box, but just cant seem to get any more speed out of this boat. Any suggestions?

 

[mr 88]

Did you buy the boat set up with the 115 ? How is the compression ? What pitch prop are you running ? Have you been on this boat motor setup and gone faster ? What is the max HP rating for the boat and what year is it ?

 

[frankrizzo]

Compression was 70 in each cylinder during a dry test. Not sure the pitch of the prop. Boat did not have a motor when i got it. The boat was previously registered with a 150hp motor. Not sure the year of the boat offhand.

 

[mr 88]

You should be within 75% of max HP rating and the older motors were rated at the crank vs todays at the prop.So your 115 is around 95-100 hp in todays rating system. You are probably overpitched and under powered. Find the max hp tag and see if your close to the minimum suggested hp.Your compression numbers are low but you may have taken them with a lousy compression gauge.

 

[mr 88]

The odds are that motor came off a smaller hull and was running a 19-21" prop. I am thinking with your setup a 17-15" would be the prop to run. I take it you do not have a tach hooked up.

 

[trevskidoo]

I have a center drive cobia year 72 with a 115 merc and I get 25 full out.