1995 Mariner 135 HP outboard

[ggundersen3]

So im looking at a pretty clean 1991 Maxum 1800XR with a 1995 Mariner 135HP outboard. Runs/starts/accelerates well. It's been on the boat since 1999. Looks good, except, according to what I looked up on boat specs that boat is rated for a 90HP. Explain to me if I'm going into dangerous territory here or is there a safe way to put a larger outboard like this one on that boat without problems? Help/advice appreciated here.

 

[wired247]

The coast guard formula for determining max hp for your boat (remote steering with over 20 inch transom ) is ...

( Length X Width X 2 ) - 90 = HP

(18 X 7.1 X 2) - 90 = 165 HP.

Even the inboard version of the same boat had a 130 HP . Coast guard doesnt differentiate between inboards and outs for HP consideration.

It might have had a 90 from the factory but thats no where near the coast guard limit for that boat. Thats a LOT of boat for 90 HP.

Normally my patent blurt is "who cares what the coast guard thinks" because I'm one of those people who overpowers everything but in your case you arent.

 

[ggundersen3]

Thanks! I didn't know that!

 

[Big Rig]

If the tag on the boat says 90 hp max, then the coast guard or the sherriffs dept can give you a ticket. The boat company rates the boat and that is what is set in stone. You probably won't have a problem with the 135, but you will get a ticket for it if they check you

 

[Dukedog]

Think its a tad different than that with "Coasties". Its not really against "their laws". They can and will in some cases order your boat back to shore if tha Officer deems it unsafe for any reason, over powered included if he/she believes its a problem (driver actin' a fool usual reason). Refusing this "command" can result in a unsafe type citation and possible "tow" to tha beach. Now State and Local laws can be different.........Way it was explained ta me on tha Texas coast.

As for tha "plate"' CG plates use ta be tha norm and still are on some but manufactures discovered with all tha big outboards out there now and lotsa boat models "over tha 20' CG hp exempt limit" it was better (their ins. and warranty)for them to limit THEIR hp ratings...... ....

 

[wired247]

If the tag on the boat says 90 hp max, then the coast guard or the sherriffs dept can give you a ticket. The boat company rates the boat and that is what is set in stone. You probably won't have a problem with the 135, but you will get a ticket for it if they check you

No he won't . Its an 18 foot boat. It doesnt have a 90 HP limit. Yes, It came with a 90 HP motor but it doesnt have a 90 HP limit. The manufacturer was being conservative when they mounted 90's on those. Ive seen quite a few of those and they usually have a 150 on the back.. As a general rule a 16 foot boat is going to have a 115-125 limit and and 18 foot is going to have a 150-175 HP limit. 19 foot and 200 -225 HP. Beyond 20 and whatever you hang on the back goes. Boat companies rate according to USCG guidelines for HP and weight limits on the tag. That particular company supplied theirs rigged with 90's but that doesnt mean thats what is written on the capacity tag

Ive got a 105 HP motor on the back of mine. Says so right on the tag on the mid section. The boat capacity tag is sun bleached blank. How handy.

 

[Chris1956]

As Wired says, an 18 foot fiberglass runabout will normally be rated for more than a 90HP motor. A 135/150 HP motor would be just fine. Is the OP sure that he is looking at the Manufacturers capacity plate and not something else?