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Hotfoot
08-16-2011, 11:22 AM
I just bought a 1995 prostar 190 with the corvette motor with 456 hours and when I start the boat it cranks a little bit before it starts and then idle is up around the 1100 rpm range but comes back down to about 700 rpm after about 15-20 seconds. It does it even after it has been running for a while (makes it hard when turning the motor on and off when teaching small kids to ski while having them climb on the platform to get there skis back on). It seems like the temperature is low about 120 degrees or cooler when running. Would this cause it to think that the engine is cold and is trying to start it as if it were just started for the first time of the day? Other than that the motor runs and idles great! Any opinions?

JimN
08-16-2011, 11:47 AM
I just bought a 1995 prostar 190 with the corvette motor with 456 hours and when I start the boat it cranks a little bit before it starts and then idle is up around the 1100 rpm range but comes back down to about 700 rpm after about 15-20 seconds. It does it even after it has been running for a while (makes it hard when turning the motor on and off when teaching small kids to ski while having them climb on the platform to get there skis back on). It seems like the temperature is low about 120 degrees or cooler when running. Would this cause it to think that the engine is cold and is trying to start it as if it were just started for the first time of the day? Other than that the motor runs and idles great! Any opinions?

Does the exhaust smell like gasoline? If it does, I would bet that one of the thermostats was removed, is stuck open or is the wrong one. Your engine uses two thermostats and the one that opens at 160 degrees needs holes in it to allow seepage.

Did you have the boat checked out before you bought it? Did you buy it privately, or from a dealer?

Where in the Midwest?

Jorski
08-16-2011, 11:53 AM
Check all hoses...

This happened to me and it was some sort of vacuum hose...caused a high idle.

In edit: Oops...just re-read your post and saw that the idle does come down after a little bit...mine didn't do that.

JimN
08-16-2011, 12:17 PM
Check all hoses...

This happened to me and it was some sort of vacuum hose...caused a high idle.

In edit: Oops...just re-read your post and saw that the idle does come down after a little bit...mine didn't do that.

Sounds like yours was the PCV hose- IIRC, that would cause the only unregulated vacuum leak, other than a manifold gasket.

dirtk38
08-16-2011, 12:27 PM
Not to hijack the thread, but my engine (Vortec MX in a '98 205) just started doing this recently. The boat cranks, idles rough for a couple seconds, then revs to a fast idle of around 1100 RPM. Exhaust does smell rich. Usually it goes back to normal after a few minutes, but the other day this continued even after I cruised for about 20 minutes and got to no-wake area of my marina ("no wake" at regular idle speeds is tough enough!). My engine was recently pulled to replace the oil pan, so maybe something wasn't put back together correctly? Engine temp is a consistent 140 degrees, and the ambient temp around here has been around 105.

Hotfoot
08-16-2011, 01:21 PM
I bought the boat from a private party in Baraboo, Wisconsin. I am located in Beaver Dam. The exhaust does smell rich. Do the thermostats that are used in the boat have to be bought from a MC dealer or can they be bought at a local parts store?

Jorski
08-16-2011, 05:45 PM
The 143 degree t-stat is a plain run of the mill unit.

The 160 degree t-stat, needs to have weep holes and is a very unique two way t-stat, due to the reverse cooling.


I would get the 160 from an MC dealer...it has to be the correct one.

LYNRDSKYNRD
08-16-2011, 06:24 PM
http://www.skidim.com/

dietdewboy
08-17-2011, 05:48 AM
Had the same issue with my 96 LT1 2 summers ago, I replaced both stat's and it cured the problem. Now my 160 degree stat has failed again in the (open position) temps are about 145 and the problem has returned. I must have got a bad one. Ordered a new one from skidim again, will post the results next week.

Hotfoot
08-17-2011, 02:04 PM
Ordered new thermostats. Will let you all know if that takes care of the problem. Thanks for your input it is much appreciated!