Issue with speed

[Matthewt]

1998 skeeter zx185 Yamaha VMAX TRP with low hours did 74 mph on the speedo when I first bought it one month ago. Since then I changed the spark plugs, and changed the lower unit oil and took the props off to see if there was fishing line around the shaft. Now Im only able to get it up to 70mph until it chine walks. My water pressure is at 25 WOT and RPMs are about 5900. Im running stock 25m props. I have been running 91 octane and I just read i should only put 87 in. Any suggestions? Raising or lowering motor? Thanks

[LittleBugMan]

First- Did you use the same plugs? Second, what was the water temp a month ago as compared to now. Third, have you switched the weight of all your tackle around any at all. Fourth. the speedo cannot ever be used to judge speed and performance. They might as well do away with it and put in a barometric pressure gauge. Fifth, do not use the higher octane gas- I was told it could cause detonation and cause damage to the power head.

[ChrisH]

get a GPS. you will be disappointed with the real speed of your boat after watching the speedo

[Skeeter Jay]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ChrisH &raquo;</TD></TR><TR><TD CLASS="quote">get a GPS. you will be disappointed with the real speed of your boat after watching the speedo

</TD></TR></TABLE>

Yep, I second the GPS statement. If thats a 150 (I'm not real familiar with what sizes they made TRP's in) then I would guess your at best running 65ish.

Also, I am going to guess that if your RPM's stayed the same on both those runs that more than likely you were running about the same speed, the speedo is just fluctuating.


Modified by Skeeter Jay at 7:36 AM 8/17/2006

[BillyJack]

Take a small drill bit and with your fingers use it to clean out the intake port in the front of your lower unit about 4 inches from the bottom. It may just have a little trash in it. Like the others are telling you though, those speedo's are not very reliable.

[dcbassman]

I had a buddy that had the exact same boat and he was able to run in the low 70's. Rumor had it that the motor had some aftermarket parts. I do know that his motor was extremly high, do a search on the TRP's I seem to remember a lot of guys running pretty close to even with the pad?