1985 190 Thundercraft with 5 liter mercruizer how fast should it go

[Lornesboat]

Hope I have this posted in the right area
I got the boat from my wife's uncle who passed away a 2 months ago the engine I was told has less then a 100 hrs on the unit and its a 1985 boat . The engine looks new.

At full throttle and 3800 RPM I'm lucky to get 36 MPH tops on a 21 P prop and the engine sounds okay but seems to take time to get on plain .

 

[Bondo]

Re: 1985 190 Thundercraft with 5 liter mercruizer how fast should it go

Hope I have this posted in the right area
I got the boat from my wife's uncle who passed away a 2 months ago the engine I was told has less then a 100 hrs on the unit and its a 1985 boat . The engine looks new.

At full throttle and 3800 RPM I'm lucky to get 36 MPH tops on a 21 P prop and the engine sounds okay but seems to take time to get on plain .

Ayuh,... Drop down to a 19" prop, 'n Try it...
Ya should be seein' 4200/ 4600 rpms at wot...
Top speed will be whatever it is...

 

[Lornesboat]

Re: 1985 190 Thundercraft with 5 liter mercruizer how fast should it go

Thanks Bond-o-

The crazy thing is he had 2 spare props both 21 p and I have no idea why. Is there a chance the prop is slipping in the rubber abit?

My wife's aunt said the boat would do 52 MPH with the prop that on the boat and the speedometer goes to 60 MPH+ yet I can't get anywhere near that(36 mph) and my GPS and speedometer are close. I know wind conditions weight etc will have an effect but not a spread of this .

 

[craze1cars]

Re: 1985 190 Thundercraft with 5 liter mercruizer how fast should it go

100 hours on a 26 year old boat? Huge red flag to me...

I would speculate it possibly has old gas, clogged fuel filter/water separator, out-of-tune carb, clogged flame arrestor, high resistance spark plug wires, maybe bad cap/rotor/(points if equipped?), spider eggs under the distributor cap? May need a tune-up, maybe had some rust in the cylinders from long term storage that could impact engine's compression, maybe dried gaskets creating an air leak/lean condition?

Anything is possible. Leave no stone unturned...this boat is an antique, but it happens to have low hours.

Also, how exactly are you driving it? I presume power trim works? Are you trimming it out as fully as possible after it gets on plane? If you're leaving the trim down, that might leave 10 to 15 mph on the table real easy...

Was this boat treated to a comprehensive tune-up and check-up before putting it back in service?

I'm not trying to cast a black shadow. Just want you to be aware that this boat might need some help outside of the prop...low hours does not always mean problem-free and ready-to-go...

To directly answer your question, I would expect high 40's out of a rig like this...somewhere between 45 and 50 realistically.

 

[Lornesboat]

Re: 1985 190 Thundercraft with 5 liter mercruizer how fast should it go

Thanks for the info LC . I will look into everything you stated. I took it into the marine place where i dock the boat and they changed the fuel filter and said the boat seemed okay. Wifes uncle changed the oil last year at the end of the season and it looks like a freshly done oil change and I have run it 8 -10 hrs now. I changed the prop and still at WOT i get only 3800 RPM. Boat trim works on the shifter handle but I noticed on the dash was a trim switch also which is disengaged for some reason ??. I suspect your right and needs a complete overhaul.


The engine sounds okay other then occasional shift issues . when I shift to reverse ..no problems but always always when I go from reverse to neutral then forward I get a stall . Sometimes it takes me 3 times to go forward.