1995 ProCraft 180 pro

[Josh256v]

1995 ProCraft 180 Pro
1990 2.4L MERC 175
No Jack-plate
23p prop
Light Load
51mph gps @5100 rpm

Motor has sat for a year or so. Do I need to get a jack plate and raise motor to gain some RPM or try a smaller pitch prop first?

Thanks

[pmgoffjr]

First...get your motor checked out, you should be turning a 23 way past 6,000.

[Josh256v]

Compression is good 110psi across the board. Would fresh gas and lines make a difference or a carb cleaning? Fuel is about a month old...

[pmgoffjr]

No way to diagnose on the internet. It could be a hundred different things.
Compression just means it’s not dead. Doesn’t mean it’s not sick.

[Josh256v]

Thanks, Pat. I'll get with the mechanic who rigged it for me. I checked the basics and we cranked it and let it run a while however we didn't do any serious diagnostics.

[Josh256v]

P.S. it comes out of the hole great.

[jarhead175]

Still needs to be looked at something isn't right on the top end if your only turning 5,100 WOT. I had a 24p and 25p for my 175 the 25p would turn 5,850 WOT and the 24p would hit the rev limiter but, had a unbelievable hole shot so I used it to ski/tube. If your prop is a true 23p you should be hitting the rev limiter with very little effort.

[Josh256v]

I put new plugs in it tonight, and going to drain all gas and run it again this weekend. I’m going off my analog tack however speed was verifies my GPS. What would contribute to such low RPM? Compression good, had fire on all cylinders when we hung the motor and I double checked that I am getting true wide open throttle.

Could bad gas be a factor?

[jarhead175]

Too many things for internet diagnostics unless you got a end supply of cash to throw parts at it. Might make a post in the Mercury form and see if they know more. Fuel system would be my guess but that's only a guess because I had a Yamaha that did the same thing years ago. If your gas was bad it would run rough from start to finish.

[Fatshaft Merc]

Go weigh the boat. It could have waterlogged foam in it.

[JohnnyO]

Go weigh the boat. It could have waterlogged foam in it.

This or a bad tach

[Josh256v]

Both of those things have crossed my mind...The fact that my buddy's rig with a 150 runs about the same...

[Josh256v]

Update: Fresh gas and new plugs had the motor running better... 54.1 mph at 5200rpm still. Going to try a 21p prop I found before buying jackplate.

[jarhead175]

Something is off......your not getting full throttle or something weird. You should be able to spin that 23 to the rev limiter with little effort. Only turning 5,200 ain't right.

[Josh256v]

Could it just be the prop is too deep? I’ve popped the cowel to ensure the carbs are opening all the way up at full throttle. If I advance the throttle the motor obviously revs beyond the 5200 so it’s plenty capable. Motor sounds and feels “strong”. I guess I’ll take it to mechanic while I’m on vacation next week.

[jarhead175]

Check with the motor guys on the Mercury form. They can walk you through some easier stuff and save you a lot of cash.

First thing I would do is test the tach to make sure your info is correct.

[mdtritn21]

Check your gas lines and make sure they are not the old red letter gray lines. I don't know what kind of fuel filter that model has but it needs to be checked/changed too. The motor will rev high on 5 cylinders so one could be down and it could be the carbs and if the fuel hasn't been treated it can destroy the rubber and the plastic in the older carb motors.

[Josh256v]

I def have fire on all 6 cylinders. We tested that the day we mounted the motor. Gotta be fuel related.

[eatmywake]

Had the same boat with a 150 Mariner EFI. I ran a 24 Tempest at 5600 rpm and 63 mph. I would think a 25 Tempest would be the ticket.

[mdtritn21]

If the carbs have never been rebuilt and it has been running ethanol gas that could be the problem. Ethanol eats all the rubber parts up in older outboard motors.