89 Glastron Futura repower question

[rob89futura]

Hi everyone, I have an 89 Glastron Futura 180 that I am looking to re-power hopefully next spring. It currently has an 89 Merc Black Max 135 hp with a 21 pitch 5 blade stainless prop. After seemingly endless hours of research I am currently leaning towards the new Mercury 150 four stroke. The boat is rated for 150 hp max. The 135 I have on there is a 20" shaft but the transom is 23" which seems odd to me. The motor is mounted as low as it can go and the cav plate is about 1 1/2" above the bottom of the transom. I haven't had any ventilation/cavitation issues with this setup which I think may be due to the 5 blade prop. So I am now wondering if the new motor should be a 20" or 25" and also what prop? If I go with the merc maybe i can use the same prop? Any input from the resident experts would be greatly appreciated. Thanks!!

 

[Bob_VT]

Re: 89 Glastron Futura repower question

Welcome to iboats.

Transom length is measured vertically straight up and down and not against the boat. It is not uncommon for people to measure the transom with the tape against the boat and come up with a higher number. Remember the shaft of the motor is set back from the transom just based on engine designs.

If you have a 20" and the plate is 1 1/2" above .......that is just about perfect. I would recommend another 20" shaft then.

Prop could be a shot in the dark and I would go with the dealers recommendation to start.

 

[rob89futura]

Re: 89 Glastron Futura repower question

Thanks for the info, that makes sense. I figured I could get help with the setup from the dealer when the time comes as well. I'll probably keep the 5 blade and try it out later on.